CA2081250C - Light detecting device - Google Patents
Light detecting device Download PDFInfo
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- CA2081250C CA2081250C CA002081250A CA2081250A CA2081250C CA 2081250 C CA2081250 C CA 2081250C CA 002081250 A CA002081250 A CA 002081250A CA 2081250 A CA2081250 A CA 2081250A CA 2081250 C CA2081250 C CA 2081250C
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- 239000004065 semiconductor Substances 0.000 claims abstract description 69
- 229910052751 metal Inorganic materials 0.000 claims abstract description 19
- 239000002184 metal Substances 0.000 claims abstract description 19
- 239000000758 substrate Substances 0.000 claims abstract description 13
- 239000004020 conductor Substances 0.000 claims description 14
- 239000000872 buffer Substances 0.000 claims description 6
- 229910000980 Aluminium gallium arsenide Inorganic materials 0.000 claims description 4
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims description 4
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 3
- WPYVAWXEWQSOGY-UHFFFAOYSA-N indium antimonide Chemical compound [Sb]#[In] WPYVAWXEWQSOGY-UHFFFAOYSA-N 0.000 claims description 3
- 229910004613 CdTe Inorganic materials 0.000 claims description 2
- 229910000661 Mercury cadmium telluride Inorganic materials 0.000 claims description 2
- 229910021417 amorphous silicon Inorganic materials 0.000 claims description 2
- 238000009792 diffusion process Methods 0.000 claims 3
- 229910001258 titanium gold Inorganic materials 0.000 claims 1
- 239000013078 crystal Substances 0.000 abstract description 19
- 239000000969 carrier Substances 0.000 description 33
- 230000003287 optical effect Effects 0.000 description 14
- GPXJNWSHGFTCBW-UHFFFAOYSA-N Indium phosphide Chemical compound [In]#P GPXJNWSHGFTCBW-UHFFFAOYSA-N 0.000 description 7
- 239000002019 doping agent Substances 0.000 description 5
- 230000002411 adverse Effects 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 3
- 238000005275 alloying Methods 0.000 description 2
- 239000003708 ampul Substances 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- KXNLCSXBJCPWGL-UHFFFAOYSA-N [Ga].[As].[In] Chemical compound [Ga].[As].[In] KXNLCSXBJCPWGL-UHFFFAOYSA-N 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 1
- 230000008033 biological extinction Effects 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012806 monitoring device Methods 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 230000003449 preventive effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000010581 sealed tube method Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by at least one potential-jump barrier or surface barrier, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier
- H01L31/105—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier the potential barrier being of the PIN type
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/022416—Electrodes for devices characterised by at least one potential jump barrier or surface barrier comprising ring electrodes
Abstract
This invention relates to a light detecting device comprising a first conduction-type semiconductor substrate, a first conduction-type semiconductor crystal layer formed on the surface of the substrate, and a second conduction-type first region formed in the semiconductor crystal layer. The first region is surrounded by a second conduction-type second region. On the surface of the semiconductor crystal layer, an electrode is formed on the first region, and a reflection preventing layer is formed on that part of the first region inside the electrode, and a device protecting film is formed on that part of the first region outside the electrode. On the semiconductor crystal layer, a metal film is formed in contact both with the semiconductor crystal layer and with the second region. This structure enables the second region to capture unnecessary charges and further to recombine and extinguish them.
Description
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Title of the Invention Light Detecting Device Background of the Invention [Field of the Invention]
This invention relates to a light detecting device for use in light output monitoring devices of semiconductor lasers, receiving devices of optical communication systems, etc.
[Prior Art]
FIG. lA is a top view of a structure of a conventional light detecting device, and FIG. 1B is a sectional view along the line X-X' in FIG. lA. As shown, the conventional light detecting device comprises a first conduction-type semiconductor substrate 1 with a first electrode 8 formed on the underside; a first conduction-type semiconductor crystal layer 2 including a light absorbing layer; and a second conduction-type first region 3 formed in the first conduction-type semiconductor crystal layer 2 by selectively diffusing a dopant. Thus formed is a pin photodiode structure. This pin photodiode structure includes an n-layer (or a p-layer) provided by the semiconductor substrate l, a p-layer (or an n-layer) provided by a first region 3, and a light detecting region 10 provided by the pn junction (the depletion layer or the i layer) . A second electrode 5 is provided on the first region 3 in the semiconductor ~~t.,~~. 1 iJf..:..1 Ia ~. t_ ~ .~... vs 1 crystal layer 2. The top of the first region 3 inside the electrode 5 is covered with a reflection preventive film 6, and the top of semiconductor crystal layer 2 outside the electrode 5 is covered with a device protective film 9.
In the semiconductor device of the above-described structure, when an reverse bias is applied, an electric field is generated in the depletion layer. Electrons and holes generated by incident light on a light detecting region 10 are divided respectively to the first conduction-type semiconductor substrate 1 and to the second conduction-type region 3 and are accelerated.
Thus a photocurrent can be taken outside. and an optical signal can be detected.
In the above-described structure of FIG. lA and 1B, when light is incident on the light detecting region 10, photo-carriers are generated in the depletion layer, and a good response characteristic can be obtained. But when light is incident outside the light detecting region 10, due to densit y gradient the generated carriers are diffused to reach the depletion layer, and are taken out in a photocurrent. The transfer of the diffused carriers is slow. When the carriers reach the light detecting region 10, adversely a tail is generated at the last transition of a light-pulse-responding waveform.
In the application of the above-described light
IILI ~~..L.~wV~~
Title of the Invention Light Detecting Device Background of the Invention [Field of the Invention]
This invention relates to a light detecting device for use in light output monitoring devices of semiconductor lasers, receiving devices of optical communication systems, etc.
[Prior Art]
FIG. lA is a top view of a structure of a conventional light detecting device, and FIG. 1B is a sectional view along the line X-X' in FIG. lA. As shown, the conventional light detecting device comprises a first conduction-type semiconductor substrate 1 with a first electrode 8 formed on the underside; a first conduction-type semiconductor crystal layer 2 including a light absorbing layer; and a second conduction-type first region 3 formed in the first conduction-type semiconductor crystal layer 2 by selectively diffusing a dopant. Thus formed is a pin photodiode structure. This pin photodiode structure includes an n-layer (or a p-layer) provided by the semiconductor substrate l, a p-layer (or an n-layer) provided by a first region 3, and a light detecting region 10 provided by the pn junction (the depletion layer or the i layer) . A second electrode 5 is provided on the first region 3 in the semiconductor ~~t.,~~. 1 iJf..:..1 Ia ~. t_ ~ .~... vs 1 crystal layer 2. The top of the first region 3 inside the electrode 5 is covered with a reflection preventive film 6, and the top of semiconductor crystal layer 2 outside the electrode 5 is covered with a device protective film 9.
In the semiconductor device of the above-described structure, when an reverse bias is applied, an electric field is generated in the depletion layer. Electrons and holes generated by incident light on a light detecting region 10 are divided respectively to the first conduction-type semiconductor substrate 1 and to the second conduction-type region 3 and are accelerated.
Thus a photocurrent can be taken outside. and an optical signal can be detected.
In the above-described structure of FIG. lA and 1B, when light is incident on the light detecting region 10, photo-carriers are generated in the depletion layer, and a good response characteristic can be obtained. But when light is incident outside the light detecting region 10, due to densit y gradient the generated carriers are diffused to reach the depletion layer, and are taken out in a photocurrent. The transfer of the diffused carriers is slow. When the carriers reach the light detecting region 10, adversely a tail is generated at the last transition of a light-pulse-responding waveform.
In the application of the above-described light
2 ~ a l', ~ A
/dc ~ i .. ~.a 1 detecting device to the optical communication, light exiting an optical fiber is focused so as to enter the light detecting region 10. In a case that a part of the light leaks outside the light detecting region 10, it leads to a lowered response speed of the light detecting device for the above-described reason. Esneciallv in a light detecting device of high response speed, since an area of the light detecting region 10 is made small to decrease a junction capacitance, light is incident by a higher ratio on the outside of the light detecting region 10, adversely a diffused carrier component resulting in a lowered response speed is increased, which leads to a decrease in a response speed of the device.
In the case that, to keep a light output of a semiconductor laser constant, a drive current of the semiconductor laser is feedback-controlled on the basis of light emitted from the rear end surface of the semiconductor laser, if light emitted by the semiconductor laser adversely spreads even outside the light detecting region 10 of the light detecting device, the diffused carriers, as described above, a carrier component which delays a response speed, which affects the feedback control.
Summary of the Invention A first object of this invention is to provide a light detecting device which has successfully solved the
/dc ~ i .. ~.a 1 detecting device to the optical communication, light exiting an optical fiber is focused so as to enter the light detecting region 10. In a case that a part of the light leaks outside the light detecting region 10, it leads to a lowered response speed of the light detecting device for the above-described reason. Esneciallv in a light detecting device of high response speed, since an area of the light detecting region 10 is made small to decrease a junction capacitance, light is incident by a higher ratio on the outside of the light detecting region 10, adversely a diffused carrier component resulting in a lowered response speed is increased, which leads to a decrease in a response speed of the device.
In the case that, to keep a light output of a semiconductor laser constant, a drive current of the semiconductor laser is feedback-controlled on the basis of light emitted from the rear end surface of the semiconductor laser, if light emitted by the semiconductor laser adversely spreads even outside the light detecting region 10 of the light detecting device, the diffused carriers, as described above, a carrier component which delays a response speed, which affects the feedback control.
Summary of the Invention A first object of this invention is to provide a light detecting device which has successfully solved the
3 i~~...:.. .1 i~~..~f I~i'. .u ... ' .J
above-described problems and improved electric characteristics, such as response speed, etc., and optical characteristics.
A second object of this invention is to provide a light detecting device comprising a first region formed of second conduction-type semiconductor and formed in a.
first conduction-type semiconductor layer, a second region formed of second conduction-type semiconductor and spaced from the first region and surrounding the first region, and a conductor layer provided both on at least one part of top surface of the semiconductor layer and on at least one part of top surface of the second region.
According to the above-described light detecting device of this invention, even if incident light leaks outside the light detecting region which is the pn junction formed between the first conduction-type semiconductor layer and the first region and adversely generates carriers, the carriers are absorbed by the second region with the result that the flow of the diffused carriers into the light detecting region can be prevented. Consequently a necessary photoelectric current alone can be taken out to an outside circuit.
Decrease of a response speed of the device can be prevented.
The first conduction-type semiconductor layer and
above-described problems and improved electric characteristics, such as response speed, etc., and optical characteristics.
A second object of this invention is to provide a light detecting device comprising a first region formed of second conduction-type semiconductor and formed in a.
first conduction-type semiconductor layer, a second region formed of second conduction-type semiconductor and spaced from the first region and surrounding the first region, and a conductor layer provided both on at least one part of top surface of the semiconductor layer and on at least one part of top surface of the second region.
According to the above-described light detecting device of this invention, even if incident light leaks outside the light detecting region which is the pn junction formed between the first conduction-type semiconductor layer and the first region and adversely generates carriers, the carriers are absorbed by the second region with the result that the flow of the diffused carriers into the light detecting region can be prevented. Consequently a necessary photoelectric current alone can be taken out to an outside circuit.
Decrease of a response speed of the device can be prevented.
The first conduction-type semiconductor layer and
4 n v l-'. (, ~ ~ ~J
~/ t ~W .l.., wI ~
1 the second region is short-circuited by a conductor layer of a metal, a semiconductor or others formed over their top surfaces, and carriers absorbed by the second region can be recombined or extinguished. Accordingly carriers are not accumulated in the second region. Even when light pulse of very high intensities is incident, no tail is generated at the last transition of a response waveform for the light pulse. Thus, electric and optical characteristics of the device can be improved.
A third object of this invention is to provide a light detecting device in which the second region has a ring-shape, and the conductor layer is provided on a surface area including a boundary between the second region and the first conduction-type semiconductor layer outside of the second region.
A fourth object of this invention is to provide a light detecting device in which the conductor layer is provided on a surface area including a boundary between the second region and the first conduction-type semiconductor layer between the first and the second regions.
A fifth object of this invention is to provide a light detecting device in which a first output electrode is connected to the top surface of the first region, and a second output electrode is connected to the underside of the substrate on the underside of the first
~/ t ~W .l.., wI ~
1 the second region is short-circuited by a conductor layer of a metal, a semiconductor or others formed over their top surfaces, and carriers absorbed by the second region can be recombined or extinguished. Accordingly carriers are not accumulated in the second region. Even when light pulse of very high intensities is incident, no tail is generated at the last transition of a response waveform for the light pulse. Thus, electric and optical characteristics of the device can be improved.
A third object of this invention is to provide a light detecting device in which the second region has a ring-shape, and the conductor layer is provided on a surface area including a boundary between the second region and the first conduction-type semiconductor layer outside of the second region.
A fourth object of this invention is to provide a light detecting device in which the conductor layer is provided on a surface area including a boundary between the second region and the first conduction-type semiconductor layer between the first and the second regions.
A fifth object of this invention is to provide a light detecting device in which a first output electrode is connected to the top surface of the first region, and a second output electrode is connected to the underside of the substrate on the underside of the first
5 I,l'. .. ~_. r... ~I
conduction-type semiconductor layer. The first output electrode and the second output electrodes outputs photoelectric currents respectively corresponding to carriers of the second conduction type and to carriers of the first conduction type.
A sixth object of this invention is to provide a light detecting device in which a first output electrode is connected to the top surface of the first electrode, and a second output electrode is provided by the conductor layer.
A seventh object of this invention is to provide a light detecting device in which the first conduction-type semiconductor layer includes a buffer layer formed on the substrate, a light absorbing layer formed on the buffer layer, and a window layer formed on the light absorbing layer, the second region being extended from the window layer into the light absorbing layer.
A eighth object of this invention is to provide a light detecting device in which the conductor layer does not completely cover the boundary between the surface of the first conduction-type semiconductor layer and the surface of the second region, but partially covers the same.
Brief Description of the Drawings FIGs. lA and 1B are view of a structure of a conventional light detecting device.
conduction-type semiconductor layer. The first output electrode and the second output electrodes outputs photoelectric currents respectively corresponding to carriers of the second conduction type and to carriers of the first conduction type.
A sixth object of this invention is to provide a light detecting device in which a first output electrode is connected to the top surface of the first electrode, and a second output electrode is provided by the conductor layer.
A seventh object of this invention is to provide a light detecting device in which the first conduction-type semiconductor layer includes a buffer layer formed on the substrate, a light absorbing layer formed on the buffer layer, and a window layer formed on the light absorbing layer, the second region being extended from the window layer into the light absorbing layer.
A eighth object of this invention is to provide a light detecting device in which the conductor layer does not completely cover the boundary between the surface of the first conduction-type semiconductor layer and the surface of the second region, but partially covers the same.
Brief Description of the Drawings FIGs. lA and 1B are view of a structure of a conventional light detecting device.
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1 FIGs. 2A and 2B are views of the light detecting device according to a first embodiment of this invention.
FIG. 3A and 3B are views of the light detecting device according to a second embodiment of this invention.
FIGs. 4A and 4B are views of the light detecting device according to a third embodiment of this invention.
Description of the Preferred Embodiments A first embodiment of this invention will be explained with reference to FIG. 2. FIG. 2A is a top view of the light detecting device according to the first embodiment, and FIG. 2B is a sectional view along the line X-X'. On an n+InP (Indium-Phosphide) semiconductor substrate 21 with an n-electrode 8 formed on the underside, there are formed a non-doped InP buffer layer 22a (carrier concentration: n=2x1015cm-3, thickness: 2 gm), a non-doped InGaAs (Indium-Gallium-Arsenide) light-detecting layer 22b (n=3x1015cm3, thickness: 3.5 Vim), and a non-doped InP window layer 22c (n=1x101~cm 3, thickness:
2 pm) for decreasing a dark current. In the light detecting layer 22b and the window layer 22c, there are formed a p-type first region 23 and a p-type second region 24 by selectively diffusing Zn. The first region has a 200 ~.m-diameter, and the second region 24(charge trapping region) has a 40 um-width. The n-type region between the first region 23 and the second region 24
1 FIGs. 2A and 2B are views of the light detecting device according to a first embodiment of this invention.
FIG. 3A and 3B are views of the light detecting device according to a second embodiment of this invention.
FIGs. 4A and 4B are views of the light detecting device according to a third embodiment of this invention.
Description of the Preferred Embodiments A first embodiment of this invention will be explained with reference to FIG. 2. FIG. 2A is a top view of the light detecting device according to the first embodiment, and FIG. 2B is a sectional view along the line X-X'. On an n+InP (Indium-Phosphide) semiconductor substrate 21 with an n-electrode 8 formed on the underside, there are formed a non-doped InP buffer layer 22a (carrier concentration: n=2x1015cm-3, thickness: 2 gm), a non-doped InGaAs (Indium-Gallium-Arsenide) light-detecting layer 22b (n=3x1015cm3, thickness: 3.5 Vim), and a non-doped InP window layer 22c (n=1x101~cm 3, thickness:
2 pm) for decreasing a dark current. In the light detecting layer 22b and the window layer 22c, there are formed a p-type first region 23 and a p-type second region 24 by selectively diffusing Zn. The first region has a 200 ~.m-diameter, and the second region 24(charge trapping region) has a 40 um-width. The n-type region between the first region 23 and the second region 24
7 ~-~!',f,'. ~! i f .f SEI 92~'L~'l~J ~-'~'J'~
1 around the first region 23 has a 10 ~.m-width. A p-electrode 25 is formed on the first region 23, and a reflection reducing film or antireflection film 26 is formed on that part of the region 23 inside the electrode 25, and a device protecting film or passivation film 2?
is farmed on that part of the first region 23 outside the electrode 25 and the window layer 22c including the second region 24.
In this structure, electrons and holes generated by incident light on the light detecting region 30 are divided respectively toward the semiconductor substrate 21 and the first region 23, and are accelerated.
Consequently a photocurrent can be taken outside, and an optical signal can be detected. If light is incident on parts other than the light detecting region 30, generated unnecessary carriers are captured by a built-in potential formed in the second region 24 embedded in the semiconductor crystal layers 22a, 22b, 22c and are hindered from entering the light detecting region 30.
Eventually a photocurrent necessary for detecting an optical signal can be taken out.
But a part of the carriers absorbed and trapped by the second region 24 are recombined and extinguished in the semiconductor crystal layer, but the other are accumulated in the second region 24. Especially when a light pulse of high intensity is inputted, a ratio of
1 around the first region 23 has a 10 ~.m-width. A p-electrode 25 is formed on the first region 23, and a reflection reducing film or antireflection film 26 is formed on that part of the region 23 inside the electrode 25, and a device protecting film or passivation film 2?
is farmed on that part of the first region 23 outside the electrode 25 and the window layer 22c including the second region 24.
In this structure, electrons and holes generated by incident light on the light detecting region 30 are divided respectively toward the semiconductor substrate 21 and the first region 23, and are accelerated.
Consequently a photocurrent can be taken outside, and an optical signal can be detected. If light is incident on parts other than the light detecting region 30, generated unnecessary carriers are captured by a built-in potential formed in the second region 24 embedded in the semiconductor crystal layers 22a, 22b, 22c and are hindered from entering the light detecting region 30.
Eventually a photocurrent necessary for detecting an optical signal can be taken out.
But a part of the carriers absorbed and trapped by the second region 24 are recombined and extinguished in the semiconductor crystal layer, but the other are accumulated in the second region 24. Especially when a light pulse of high intensity is inputted, a ratio of
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1 carriers extinguished by recombination is low, and most remaining carriers are accumulated in the second region 24. Resultantly a built-in potential formed in the second region becomes weak, and a ratio of carriers trapped by the second region is lowered. Diffused carriers having a lower transfer speed flow into the light detecting region 30, and a tail is generated at the last transition of a response waveform for the light pulse. Thus, electric and optical characteristics of the device are affected.
The above-described affection is more remarkable especially in the case that the second region 24 is not exposed at the end surface of the second region 24. In this case, recombinations and extinctions of the carriers hardly take place, and carriers are accordingly accumulated in the second region 24. In this state, as described above, electric and optical characteristics are affected. In the case that the second region 24 is exposed at an end surface of the device, carriers tend to leak at the end surface and to be recombined.
Consequently most carriers are not accumulated in the second region 24, and accardingly a built-in potential in the second region 24 does nat tend to be lowered.
Consequently a ratio of carriers trapped by the second region 24 does not lower with the result that electric and optical characteristics are not seriously affected.
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1 carriers extinguished by recombination is low, and most remaining carriers are accumulated in the second region 24. Resultantly a built-in potential formed in the second region becomes weak, and a ratio of carriers trapped by the second region is lowered. Diffused carriers having a lower transfer speed flow into the light detecting region 30, and a tail is generated at the last transition of a response waveform for the light pulse. Thus, electric and optical characteristics of the device are affected.
The above-described affection is more remarkable especially in the case that the second region 24 is not exposed at the end surface of the second region 24. In this case, recombinations and extinctions of the carriers hardly take place, and carriers are accordingly accumulated in the second region 24. In this state, as described above, electric and optical characteristics are affected. In the case that the second region 24 is exposed at an end surface of the device, carriers tend to leak at the end surface and to be recombined.
Consequently most carriers are not accumulated in the second region 24, and accardingly a built-in potential in the second region 24 does nat tend to be lowered.
Consequently a ratio of carriers trapped by the second region 24 does not lower with the result that electric and optical characteristics are not seriously affected.
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1 However, in applying the light detecting device according to this embodiment to various optical devices, it is necessary to extinguish generated carriers more quickly to maintain a state in which no carriers are accumulated in the second region 24 even when light of high intensity is inputted.
Here to eliminate the above-described influence, in addition to the above-described structure, as shown in FIG. 2, a metal film 31 is formed on the semiconductor crystal layers 22a, 22b, 22c so as to be in contact both with the p-type second region 24 and with the n-type region outside the second region 24. This metal film 31 is formed by alloying Au/Zn/Au and is contact over a 10 ~.m-width both with the second region 24 and with the n-type region outside the second region 24. The area of the metal film 31 is 20 gm x 40 um.
It is preferable that the light detecting layer 22b has a thickness of 2 9 um for good absorbing efficiency of incident light, but the width is not necessarily limited to this range. The n-type region between the p-type first region 23 and the p-type second region 24 preferably has a width of 2 40 um, but the width is not necessarily limited to the range. The shape and width of the metal film 31 in contact with the n-type region and with the p-type second region 24 are not necessarily limited to the above.
lnt. I 'A.~ r... w 1 In the above-described structure, when light is incident on regions other than the light detecting region 30, unnecessary ones of the generated carriers are captured by the second region 24 which is a charge trapping region. Consequently no tail is generated at the last transition or the fall of a light pulse, and only a photocurrent necessary for the detection of an optical signal can be taken out. The captured carriers are recombined and extinguished by the metal film 31 short-circuiting the window layer 22c and the second region 24 and are not accumulated in the second region 24. Accordingly a ratio of carriers captured by the second region 24 does not lowered, and electric characteristics and optical characteristics are not affected. In terms of the structure, it is not necessary to provide an extra electrode and connect the same to the electrode 28 in order to take out accumulated carriers.
The device can have a simplified structure. The diameter of the region 23, etc. are not limited to this embodiment.
The light detecting device according to a second embodiment of this invention will be explained with reference to FIG. 3. FIG. 3A is a top view of the light detecting device according to this embodiment, and FIG.
3B is a sectional view along the line X-X'. On a Fe doped InP substrate 21 (specific resistance: - 1MS2~em), '1 ~/l f ~~~ W .r...~-y SEI 92-2'1 1 there are formed a non-doped InP buf fer layer 22a (n=ix1015cm3, thickness: 1 gm), a non-doped InGaAs light detecting layer 22b (n=1x1015cm3, thickness: 4 um), and a non-doped window layer 22c (n=2x1015cm3, thickness: 3 um). In the light detecting layer 22b and the window layer 22c there are formed a p-type first region 23 and a p-type second region 24 by selectively diffusing Zn by ampul or sealed tube method. The first region has a 300 ~.m-diameter. Because of this region 23, a structure including the pn junction as the light detecting region 30 can be provided. The n-type region between the first region 23 and the second region 24 has a 20 ~.m-width. On the first region 23 there is provided a p-electrode 25.
A antireflection film 26 is provided on that part of the region 23 inside the electrode 25, and a device protecting film 27 is formed on that part of the region 23 outside the electrode 25 and on the second region 24 in the window layer 22 c. An n-electrode 48 for the light detecting device is formed on that part of the InP
window layer 22c outside the second region 24 and on a part of the second region 24. the n-electrode 48 has a 330 um-inner diameter and is over the second region 24 by 5 ~.m .
In the above-described structure, the electrode 48 formed in contact with both the p-type second region 24 and the n-type window layer 22c can function as the n-I.r,I-'~. ~ ~t f .r.., ., v rr .~
SEI 92-2"l 1 electrode 28 (FIG. 2) for taking out a photoelectric current, and as the metal film 31 (FIG. 2) for recombining carriers captured by the second region (charge trapping region ) 24. The second embodiment has a simple structure but can produce the same advantageous effect as the first embodiment.
The light detecting device according to a third embodiment of this invention will be explained with reference to FIG. 4. FIG. 4A is a top view of the light detecting device according to the third embodiment of this invention, and FIGS. 4B is a sectional view along the line X-X'. As shown, on the surface of an n-type (first conduction-type) semiconductor substrate 21 with an n-electrode 28 formed on the underside, there is formed an n-type semiconductor crystal layer 22. A p-type (second conduction-type) first region 23 is formed on the semiconductor crystal layer 22 by diffusing a dopant by ampul method. The first region 23 has a 300 ~.m-diameter. The first region 23 forms a pn junction which is a light detecting region 30. This first region 23 is surrounded by a p-type second region 24 which is formed as a charge trapping region by diffusing a dopant.
The second region 24 is spaced from the first region 23 by 20 um. A p-type (second conduction-type) electrode 25 is provided on the first region 23. An antireflection film 26 is formed on that part of the first region 23 ,t .
L~ ~. m -.... wJ
1 inside the electrode 25, and a device protecting film 2'7 is formed on that part of the first region 23 outside the electrode 25 and on the semiconductor crystal layer 22 including the second region 24. A metal film 31 is provided in contact with the semiconductor crystal layer 22 and with the second region 24. In this embodiment, the metal film 31 contacts over a 5 pm-width respectively with the semiconductor crystal layer 22 and with the second region 24 so that carriers captured by the second region can be recombined and annihilated. The metal film 31 has an area of 10 gm x 50 Vim.
In this structure as well as that according to the first embodiment, unnecessary carriers are collected in the second region further to be recombined and extinguished by the metal film 31. Accordingly diffused carriers never affect electric characteristics of the device, such as response speed etc. , and optical characteristics thereof. But a disadvantage of this embodiment is that because of the location of the metal film 31, whose reflectance is high, near the first region 23, in comparison with the first embodiment light tends to leak to the surroundings.
The semiconductor materials and their dimensions referred to above are merely exemplified and can be varied in accordance with applications, wavelengths to be used, etc. For example, the materials of the ' wf'~r'_ 1 ~~~'f~
ir< ~ e...~.vy.J.
semiconductors may be compound semiconductors, such as GaAs (Gallium-Arsenide), InGaAsP (Indium-Gallium-Arsenide-Phosphide), AlGaAs (Aluminium-Gallium-Arsenide), CdTe (Cadmium-Telaride), HgCdTe (Mercury-Cadmium-Telaride), InSb (Indium-Antimonide). etc., or Si (Silicon), Ge (Germanium), ete. In the case that AlGaAs is used for the light absorbing layer, GaAs or others, for example, can be used for the window layer. As dopants, Be (Beryllium), Cd (Cadmium), etc. may be used.
The dopants ma3T be added by ion implantation or others.
The second region and the semiconductor crystal layer is not necessarily short-circuited by a metal film, but may be short-circuited by a semiconductor layer. The metal film may be formed e.g. , by vacuum evaporating an AuGeNi alloy or by depositing Au/Ge/Ni on the semiconductor crystal layer and alloying the same. The semiconductor layer may be provided by, e.g., amorphous silicon.
1 However, in applying the light detecting device according to this embodiment to various optical devices, it is necessary to extinguish generated carriers more quickly to maintain a state in which no carriers are accumulated in the second region 24 even when light of high intensity is inputted.
Here to eliminate the above-described influence, in addition to the above-described structure, as shown in FIG. 2, a metal film 31 is formed on the semiconductor crystal layers 22a, 22b, 22c so as to be in contact both with the p-type second region 24 and with the n-type region outside the second region 24. This metal film 31 is formed by alloying Au/Zn/Au and is contact over a 10 ~.m-width both with the second region 24 and with the n-type region outside the second region 24. The area of the metal film 31 is 20 gm x 40 um.
It is preferable that the light detecting layer 22b has a thickness of 2 9 um for good absorbing efficiency of incident light, but the width is not necessarily limited to this range. The n-type region between the p-type first region 23 and the p-type second region 24 preferably has a width of 2 40 um, but the width is not necessarily limited to the range. The shape and width of the metal film 31 in contact with the n-type region and with the p-type second region 24 are not necessarily limited to the above.
lnt. I 'A.~ r... w 1 In the above-described structure, when light is incident on regions other than the light detecting region 30, unnecessary ones of the generated carriers are captured by the second region 24 which is a charge trapping region. Consequently no tail is generated at the last transition or the fall of a light pulse, and only a photocurrent necessary for the detection of an optical signal can be taken out. The captured carriers are recombined and extinguished by the metal film 31 short-circuiting the window layer 22c and the second region 24 and are not accumulated in the second region 24. Accordingly a ratio of carriers captured by the second region 24 does not lowered, and electric characteristics and optical characteristics are not affected. In terms of the structure, it is not necessary to provide an extra electrode and connect the same to the electrode 28 in order to take out accumulated carriers.
The device can have a simplified structure. The diameter of the region 23, etc. are not limited to this embodiment.
The light detecting device according to a second embodiment of this invention will be explained with reference to FIG. 3. FIG. 3A is a top view of the light detecting device according to this embodiment, and FIG.
3B is a sectional view along the line X-X'. On a Fe doped InP substrate 21 (specific resistance: - 1MS2~em), '1 ~/l f ~~~ W .r...~-y SEI 92-2'1 1 there are formed a non-doped InP buf fer layer 22a (n=ix1015cm3, thickness: 1 gm), a non-doped InGaAs light detecting layer 22b (n=1x1015cm3, thickness: 4 um), and a non-doped window layer 22c (n=2x1015cm3, thickness: 3 um). In the light detecting layer 22b and the window layer 22c there are formed a p-type first region 23 and a p-type second region 24 by selectively diffusing Zn by ampul or sealed tube method. The first region has a 300 ~.m-diameter. Because of this region 23, a structure including the pn junction as the light detecting region 30 can be provided. The n-type region between the first region 23 and the second region 24 has a 20 ~.m-width. On the first region 23 there is provided a p-electrode 25.
A antireflection film 26 is provided on that part of the region 23 inside the electrode 25, and a device protecting film 27 is formed on that part of the region 23 outside the electrode 25 and on the second region 24 in the window layer 22 c. An n-electrode 48 for the light detecting device is formed on that part of the InP
window layer 22c outside the second region 24 and on a part of the second region 24. the n-electrode 48 has a 330 um-inner diameter and is over the second region 24 by 5 ~.m .
In the above-described structure, the electrode 48 formed in contact with both the p-type second region 24 and the n-type window layer 22c can function as the n-I.r,I-'~. ~ ~t f .r.., ., v rr .~
SEI 92-2"l 1 electrode 28 (FIG. 2) for taking out a photoelectric current, and as the metal film 31 (FIG. 2) for recombining carriers captured by the second region (charge trapping region ) 24. The second embodiment has a simple structure but can produce the same advantageous effect as the first embodiment.
The light detecting device according to a third embodiment of this invention will be explained with reference to FIG. 4. FIG. 4A is a top view of the light detecting device according to the third embodiment of this invention, and FIGS. 4B is a sectional view along the line X-X'. As shown, on the surface of an n-type (first conduction-type) semiconductor substrate 21 with an n-electrode 28 formed on the underside, there is formed an n-type semiconductor crystal layer 22. A p-type (second conduction-type) first region 23 is formed on the semiconductor crystal layer 22 by diffusing a dopant by ampul method. The first region 23 has a 300 ~.m-diameter. The first region 23 forms a pn junction which is a light detecting region 30. This first region 23 is surrounded by a p-type second region 24 which is formed as a charge trapping region by diffusing a dopant.
The second region 24 is spaced from the first region 23 by 20 um. A p-type (second conduction-type) electrode 25 is provided on the first region 23. An antireflection film 26 is formed on that part of the first region 23 ,t .
L~ ~. m -.... wJ
1 inside the electrode 25, and a device protecting film 2'7 is formed on that part of the first region 23 outside the electrode 25 and on the semiconductor crystal layer 22 including the second region 24. A metal film 31 is provided in contact with the semiconductor crystal layer 22 and with the second region 24. In this embodiment, the metal film 31 contacts over a 5 pm-width respectively with the semiconductor crystal layer 22 and with the second region 24 so that carriers captured by the second region can be recombined and annihilated. The metal film 31 has an area of 10 gm x 50 Vim.
In this structure as well as that according to the first embodiment, unnecessary carriers are collected in the second region further to be recombined and extinguished by the metal film 31. Accordingly diffused carriers never affect electric characteristics of the device, such as response speed etc. , and optical characteristics thereof. But a disadvantage of this embodiment is that because of the location of the metal film 31, whose reflectance is high, near the first region 23, in comparison with the first embodiment light tends to leak to the surroundings.
The semiconductor materials and their dimensions referred to above are merely exemplified and can be varied in accordance with applications, wavelengths to be used, etc. For example, the materials of the ' wf'~r'_ 1 ~~~'f~
ir< ~ e...~.vy.J.
semiconductors may be compound semiconductors, such as GaAs (Gallium-Arsenide), InGaAsP (Indium-Gallium-Arsenide-Phosphide), AlGaAs (Aluminium-Gallium-Arsenide), CdTe (Cadmium-Telaride), HgCdTe (Mercury-Cadmium-Telaride), InSb (Indium-Antimonide). etc., or Si (Silicon), Ge (Germanium), ete. In the case that AlGaAs is used for the light absorbing layer, GaAs or others, for example, can be used for the window layer. As dopants, Be (Beryllium), Cd (Cadmium), etc. may be used.
The dopants ma3T be added by ion implantation or others.
The second region and the semiconductor crystal layer is not necessarily short-circuited by a metal film, but may be short-circuited by a semiconductor layer. The metal film may be formed e.g. , by vacuum evaporating an AuGeNi alloy or by depositing Au/Ge/Ni on the semiconductor crystal layer and alloying the same. The semiconductor layer may be provided by, e.g., amorphous silicon.
Claims (27)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A light detecting device comprising:
a first region formed of second conduction-type semiconductor and embedded in a first conduction-type semiconductor layer;
a second region formed of second conduction-type semiconductor and embedded so as to be spaced from and surround the first region; and a conductor layer provided both on at least one part of top surface of the first conduction-type semiconductor layer and on at least one part of top surface of the second region.
a first region formed of second conduction-type semiconductor and embedded in a first conduction-type semiconductor layer;
a second region formed of second conduction-type semiconductor and embedded so as to be spaced from and surround the first region; and a conductor layer provided both on at least one part of top surface of the first conduction-type semiconductor layer and on at least one part of top surface of the second region.
2. A light detecting device according to claim 1, wherein the conductor layer is a metal film.
3. A light detecting device according to claim 1, wherein the conductor layer is a conductive semiconductor layer.
4. A light detecting device according to claim 1, wherein the second region has an annular shape, and the conductor layer is provided on a surface area including a boundary between the second region and a part of the first conduction-type semiconductor layer outside the second region.
5. A light detecting device according to claim 1, wherein the conductor layer is provided on a surface area including a boundary between the second region and a part of the first conduction-type semiconductor layer between the first and the second regions.
8. A light detecting device according to claim 1, wherein a first output electrode is connected to the top surface of the first region, and a second output electrode is connected to the underside of a substrate provided on the underside of the first conduction-type semiconductor layer.
7. A light detecting device according to claim 4, wherein a first output electrode is connected to the top surface of the first region, and a second output electrode is provided by the conductor layer.
8. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer comprises a buffer layer formed on a substrate, a light absorbing layer formed on the buffer layer, and a window layer formed on the light absorbing layer; and the second region is extended from the window layer to the light absorbing layer.
9. A light detecting device according to claim 1, wherein the conductor layer partially covers the boundary between the surface of the first conductive-type semiconductor layer and the surface of the second region.
10. A light detecting device according to claim 2, wherein the metal film is formed of an AuZn alloy.
11. A light detecting device according to claim 2, wherein the metal film is formed of an AuGeNi alloy.
12. A light detecting device according to claim 3, wherein the conductive semiconductor layer is formed of amorphous Si.
13. A light detecting device according to claim 1, wherein the first conduction-type semiconductor-layer is formed of InGaAs.
14. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer is formed of GaAs.
15. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer is formed of InGaAsP.
16. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer is formed of AlGaAs.
17. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer is formed of CdTe.
18. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer is formed of HgCdTe.
19. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer is formed of InSb.
20. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer is formed of Si.
21. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer is formed of Ge.
22. A light detecting device according to claim 1, wherein the first and the second regions are formed by the diffusion of Zn.
23. A light detecting device according to claim 1, wherein the first and the second regions are formed by the diffusion of Be.
24. A light detecting device according to claim 1, wherein the first and the second regions are formed by the diffusion of Cd.
25. A light detecting device according to claim 5, wherein a first output electrode is connected to the top surface of the first region, and a second output electrode is provided by the conductor layer.
26. A light detecting device according to claim 2, wherein the metal film is formed of a TiAu.
27. A light detecting device according to claim 1, wherein the first conduction-type semiconductor layer is formed of InP.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3279904A JP3047385B2 (en) | 1991-10-25 | 1991-10-25 | Light receiving element |
| JP279904/1991 | 1991-10-25 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2081250A1 CA2081250A1 (en) | 1993-04-26 |
| CA2081250C true CA2081250C (en) | 2000-02-15 |
Family
ID=17617539
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002081250A Expired - Fee Related CA2081250C (en) | 1991-10-25 | 1992-10-23 | Light detecting device |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US5420418A (en) |
| EP (1) | EP0538878B1 (en) |
| JP (1) | JP3047385B2 (en) |
| KR (1) | KR950014288B1 (en) |
| CA (1) | CA2081250C (en) |
| DE (1) | DE69212108T2 (en) |
| DK (1) | DK0538878T3 (en) |
| ES (1) | ES2091381T3 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05235396A (en) * | 1992-02-24 | 1993-09-10 | Sumitomo Electric Ind Ltd | Semiconductor photoreceptor |
| JPH09289333A (en) * | 1996-04-23 | 1997-11-04 | Mitsubishi Electric Corp | Semiconductor photosensitive element |
| JP3828982B2 (en) * | 1997-04-14 | 2006-10-04 | 三菱電機株式会社 | Semiconductor photo detector |
| US6043550A (en) * | 1997-09-03 | 2000-03-28 | Sumitomo Electric Industries, Ltd. | Photodiode and photodiode module |
| JP3221402B2 (en) * | 1998-06-22 | 2001-10-22 | 住友電気工業株式会社 | Light receiving element and light receiving device |
| US7288825B2 (en) * | 2002-12-18 | 2007-10-30 | Noble Peak Vision Corp. | Low-noise semiconductor photodetectors |
| WO2021074967A1 (en) * | 2019-10-15 | 2021-04-22 | 日本電信電話株式会社 | Light-receiving element |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61172381A (en) * | 1984-12-22 | 1986-08-04 | Fujitsu Ltd | Inp group compound semiconductor device |
| JPH0799782B2 (en) * | 1985-06-18 | 1995-10-25 | 株式会社ニコン | Semiconductor photodetector |
| DE3650287T2 (en) * | 1985-09-24 | 1995-08-10 | Toshiba Kawasaki Kk | Semiconductor photodetector with a two-stage contamination profile. |
| JPH04111479A (en) * | 1990-08-31 | 1992-04-13 | Sumitomo Electric Ind Ltd | Light-receiving element |
| JPH05235396A (en) * | 1992-02-24 | 1993-09-10 | Sumitomo Electric Ind Ltd | Semiconductor photoreceptor |
-
1991
- 1991-10-25 JP JP3279904A patent/JP3047385B2/en not_active Expired - Fee Related
-
1992
- 1992-10-23 ES ES92118177T patent/ES2091381T3/en not_active Expired - Lifetime
- 1992-10-23 CA CA002081250A patent/CA2081250C/en not_active Expired - Fee Related
- 1992-10-23 EP EP92118177A patent/EP0538878B1/en not_active Expired - Lifetime
- 1992-10-23 DE DE69212108T patent/DE69212108T2/en not_active Expired - Fee Related
- 1992-10-23 DK DK92118177.2T patent/DK0538878T3/en active
- 1992-10-24 KR KR1019920019628A patent/KR950014288B1/en not_active IP Right Cessation
-
1994
- 1994-05-06 US US08/238,784 patent/US5420418A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DE69212108D1 (en) | 1996-08-14 |
| ES2091381T3 (en) | 1996-11-01 |
| CA2081250A1 (en) | 1993-04-26 |
| EP0538878A2 (en) | 1993-04-28 |
| KR950014288B1 (en) | 1995-11-24 |
| JP3047385B2 (en) | 2000-05-29 |
| EP0538878B1 (en) | 1996-07-10 |
| DE69212108T2 (en) | 1997-02-20 |
| EP0538878A3 (en) | 1993-08-04 |
| US5420418A (en) | 1995-05-30 |
| DK0538878T3 (en) | 1996-11-11 |
| JPH05121777A (en) | 1993-05-18 |
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