CA1064150A - Light activated thyristor - Google Patents
Light activated thyristorInfo
- Publication number
- CA1064150A CA1064150A CA259,920A CA259920A CA1064150A CA 1064150 A CA1064150 A CA 1064150A CA 259920 A CA259920 A CA 259920A CA 1064150 A CA1064150 A CA 1064150A
- Authority
- CA
- Canada
- Prior art keywords
- junction
- thyristor
- projection
- gate electrode
- zone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000969 carrier Substances 0.000 claims abstract description 16
- 238000010304 firing Methods 0.000 claims description 9
- 230000005855 radiation Effects 0.000 claims description 9
- 239000004065 semiconductor Substances 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 3
- 239000002674 ointment Substances 0.000 description 17
- 230000002411 adverse Effects 0.000 description 1
- 239000002800 charge carrier Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000001960 triggered effect Effects 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
- H01L31/111—Devices sensitive to infrared, visible or ultraviolet radiation characterised by at least three potential barriers, e.g. photothyristor
- H01L31/1113—Devices sensitive to infrared, visible or ultraviolet radiation characterised by at least three potential barriers, e.g. photothyristor the device being a photothyristor
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention pertains to a light acti-vated thyristor which increases the current density of light-generated carriers by means of a low resistance path from an area of carrier generation in a base zone of a first conductivity type into a portion of an adjacent emit-ter zone of a second conductivity type. In one embodiment the low resistance path takes the form of an annular gate electrode affixed to the base zone and having a projection bordering the base-emitter PN junction. In another embodi-ment the low resistance path takes the form of a ballast segment disposed in the base zone, the ballast segment hav-ing an opening for funnelling the carriers to the base-emitter PN junction.
The present invention pertains to a light acti-vated thyristor which increases the current density of light-generated carriers by means of a low resistance path from an area of carrier generation in a base zone of a first conductivity type into a portion of an adjacent emit-ter zone of a second conductivity type. In one embodiment the low resistance path takes the form of an annular gate electrode affixed to the base zone and having a projection bordering the base-emitter PN junction. In another embodi-ment the low resistance path takes the form of a ballast segment disposed in the base zone, the ballast segment hav-ing an opening for funnelling the carriers to the base-emitter PN junction.
Description
~064150 BACKGROUND OF THE INVENTION
Field of the Invention The present invention pertains to light activated semiconductor switching devices, and particularly to thyris-tors which can be fired by a light-emitting diode.
Descri~tion of the Prior Art , An important design criterion of light activated thyristors is the ability to be fired (triggered) by means of a low intensity radiation source, as for example, a light-emitting diode (LED). A disadvantage associated with suchuse of LED's to fire thyristors is the relatively low density of carriers generated in the semiconductor body, which re-sults in a slow firing rate. It is known that slow firing causes hot-spots in the semiconductor body due to high load current densities localized at random points where initial .
-~F
46,762 conduction sets in, thereby damaging the thyristor. The present invention, therefore, is addressed to the problem of making a light activated thyristor which responds more effectively to a low intensity radiation source.
Prior art thyristors are provided with base-emitter short circuits (shunts), which improve dv/dt response. Un- ~
fortunately, the shunts also drain off the light-generated -carriers by providing low impedance paths to the emitter electrode directly from the area in the base where the car-10 riers are generated. While it is true that a reduction in ;~
base-emitter shunting increases the current density of light-generated carriers passing through the base-emitter PN ~unc-tion, such a reduction in shunting also adversely affects the dv/dt response. Thus, those skilled in the art will recognize that a reduction in shunting is an impractical trade-off, and that a means of increasing the current density of light-generated carriers crossing the base-emitter PN ~unction is required, while at the same time maintaining adequate shunt-ing.
SUMMARY OF THE INVENTION
In accordance with the present invention, a light-activated thyristor, which has an improved firing rate in response to low intensity radiation, comprises means provid-ing a low resistance path from a source area of light-generated carriers to a portion of a PN ~unction ad~acent to the source area, whereby the current density of carriers crossing the PN
junction is sufficient to fire the thyristor at the improved rate.
In one preferred embodiment, the low resistance path means comprises a gate electrode disposed between the source 46,762 -1C~64~50 area and the PN ~unction, the gate electrode having a pro-~ection bordering from about one fourth to about one half the length of the PN junction.
In another embodiment, the low resistance path means comprises a ballast segment disposed between the source area and the PN junction, the ballast segment hav-ing an opening bordering from about one fourth to about one half the length of the PN junction.
In still another embodiment, the low resistance path means comprises a ballast segment disposed between the source area and the PN junction, and a gate electrode in juxtaposition over the ballast segment, the ballast segment having an opening, the gate electrode having a projection in juxtaposition over the opening, the proJection bordering from about one fourth to about one half the length of the !
PN junction.
In a further embodiment, the low resistance path means comprises a closed-loop ballast segment surrounding the source area, and a gate electrode in ~uxtaposition over the ballast segment, the gate electrode having a projection overlapping the ballast segment, the pro~ection bordering from about one fourth to about one half the length of the PN ~unction.
BRIEF DESCRIPTION OF THE ~RAWINGS
Figures 1 and 2 are respectively a partial cross-section and a partial plan view of a first preferred embodi-ment of the present invention;
Flgures 3 and 4 are respectively a partial cross-section and a partial plan view of a second embodiment of the present invention;
46,762 SO
Figure 5 is a plan view of a third embodlment of the present invention;
Figure 6 is a plan view of a fourth embodiment of the present invention; and, Figure 7 is a plan view of an embodiment of the present invention having an auxiliary thyristor.
DESCRIPTION OF THE PR~FERRED EMBODIMENT
Referring to Figures 1 and 2, a portion of a light , activated thyristor 100 illustrates a first preferred embod-iment of the invention. The thyristor 100 comprises a body 101 of semiconductor material typically having four zones of alternate conductivity type produced in a known manner, only three of which are explicitly shown for ease of illustration.
An emitter zone 102 of a first conductivity type is situated in body 101 ad~acent to a top major surface of the body 101.
A base zone 103 of a second conductivity type is situated beneath emitter zone 102. An interior zone 104 of the first conductivity type is situated beneath the base zone 103.
There is at least one additional zone (not shown) situated beneath zone 104, such as an anode zone of the second con-ductivity type bordering a bottom major surface (not shown) of the body 101. An emitter electrode 105 is affixed to the body 101 contacting the emitter zone 102 and small shunt por-tions 106 of the base zone 103, the shunts 106 providing base-emitter short circuits known in the art. A gate electrode 107 is affixed to the body 101 contacting the base zone 103 as shown. The gate electrode 107 takes the shape of a closed-loop or annulus having a projection 108 extending outward.
The gate electrode 107 encompasses a portion 109 of the top major surface above the base zone 103, which constitutes a - 46,762 ~ ~ 4~50 source area of llght-generated carriers. Associated with the thyristor 100 ls a means (designated by the superimposed arrows) for illuminating the base zone 103 with low intensity radiation, comprising for example a LED. Interfacing base zone 103 and emitter zone 102 is a PN junction 110, which preferably ~orms a closed-loop at its intersection with the top ma~or surface of body 101, thereby circumscribing the gate electrode 107 and the carrier source area 109 therein.
The pr,o~ection 108 borders a fractional portion of the closed-loop of the PN ~unction 110, the separation distance betweenthe projection 108 and the PN junction 110 being uniform as shown.
When source area 109 is illuminated with low in-tensity radiation, pairs of charge carriers are produced in the base zone 103 within the annular gate electrode 107.
Carriers of one polarity travel to the electrode 107, which causes a current to flow through the pro~ection 108 into the narrow strip of base zone 103 between the pro~ection 108 and the PN ~unction 110. The current density is thereby concen-trated by the shape of the electrode 107. The concentrated - current then flows through PN ~unction 110 into emitter zone 102 and from there into emitter electrode 105. Pro~ection 108, being metallic, provides a low resistance path relative to the semiconductor material of base zone 103 surrounding the electrode 107. Consequently, most of the light-generated current flows via pro~ection 108 through PN ~unction 110.
Furthermore, since the pro;ection 108 borders a fractional portion of the length of the surrounding PN ~unction 110, the current density through the PN ~unction 110 is sufficient to fire the thyristor 100 at a rate faster than a similar prior 46,762 ~ 5 O
art device without the projection 108. Thus, the incidence of load current hot-spotting found in slower prior art de-vices is substantially reduced in thyristors of the present invention. The fractional portion of the length of the PN
~unction 110 bordered by projection 108 should be less than one half the total length of the intersection of PN ~unction 110 with the surface of body 101 along a line immediately surrounding the gate electrode 107. Preferably, however, pro~ection 108 borders about one fourth such length of PN
~unction 110 at the surface.
When thyristor 100 is operating under load condi-tions, emltter e]ectrode 105 is connected to an external cir-cuit while gate electrode 107 remains free floating. There-fore, any changes in circuit voltage (dv/dt) are impressed on thyristor 100 at emitter electrode 105. Semiconductor body 101 has a capacitance which results in a current in the presence of a dv/dt. As shown by the arrowpaths in Figure 1, such dv/dt current, as long as it does not lead to turn-on, flows upward into base zone 103 and then essentially symmet-rically radially outward and through shunts 106 to the emitterelectrode 105. The pro~ection 108 has in this case no influ-ence on the current distribution. Only when the dv/dt-current becomes so high that the current fraction flowing into emitter 110 will reach the same order of magnitude as that flowing into the shunts 106, will the current begin to flow preferably through pro~ection 108. Thus for very high dv/dt thyristor 100 has a somewhat increased sensitivity to dv/dt firing in comparison to prior art thyristors.
Now referring to Figures 3 and 4, wherein similar 3 numerals designate similar parts, a thyristor 200 is shown :: :
46,762 16~ 50 which has an alternate means for providing a low resistance path for light~generated carriers. A relatively low resis-tance path is created by increasing the resistance around source area 209 by means of a ballast segment 211 of the same conductivity type as emitter zone 202. As seen in Figure 4, ballast segment 211 is C-shaped, which provldes an opening as a low resistance path means from the source area 209 to the PN junction 210. Preferably the ballast segment 211 sur-rounds most of the source area 209, such that the opening borders about one fourth of the length of the PN junction 210 surrounding the ballast segment 211. Ballast segment 211 can be formed by known masking techniques simultaneously with the diffusion of emitter zone 202.
The functioning of thyristor 200 is analogous to that of thyristor 100. When source area 209 is illuminated with low intensity radiation, carriers are generated which flow via the relatively low resistance path of the opening in ballast segment 211 through the portion of PN junction 210 bordering the opening. The current density is thereby concentrated in the low resistance path causing firing to occur at an improved rate similarly as described above.
Now referring to Figure 5, similar numerals desig-nating similar parts, a thyristor 300 is shown which essen-tially combines both low resistance path means of thyristors 100 and 200. Gate electrode 307 lies in juxtaposition over ballast segment 311, such that gate electrode 307 overlaps the inner portion of ballast segment 311 and the ad~acent source area 209 disposed within the ballast segment 311 as shown. Projection 308 lies in juxtaposition over an opening in the ballast segment 311.
46,762 ` 1~64150 Now referring to Fig~re 6, similar numerals desig-nating similar parts, a thyristor 400 is shown which is a slight structural modification of thyristor 300 of Figure 5. -Thyristor 400 of Figure 6 has a closed-loop ballast segment 412 surrounding source area 409. Gate electrode 407 lies in ~uxtaposition over ballast segment 412, gate electrode 407 having a projection 408 overlapping the ballast segment 412 to provide a low resistance path from source area 409 to a portion of PN ~unction 410 bordering the pro~ection 408.
Now referring to Figure 7, similar numerals desig-nating similar parts, a thyristor 500 is shown which incor-porates by way of example the low resistance path means of thyristor 300 into a thyristor structure having a so-called amplifying gate structure or integrated auxiliary thyristor structure. Thyristors with amplifying gates are known in the art. It is to be understood that any one of the embodiments described above can be successfully combined with an ampli-fying gate thyristor. In particular, thyristor 500 comprises a secondary emitter electrode 505 affixed to secondary emitter zone 502, and an amplifying gate electrode 515 affixed to an auxiliary emitter zone 516. The amplifying gate electrode 515 fires the main thyristor (not shown) in a known manner.
The electrode 505 has a projection 513 extending from zone 502 into the base zone 503 thereby bordering PN ~unction 514.
The projection 513 iS symmetrically disposed radially outward from pro~ection 508, but could also be positioned at any angle.
When thyristor 500 is forward biased and source area 509 is illuminated with low intensity radiation, carriers are generated which flow via pro~ection 508 through PN ~unction 3Q 510 thereby firing emitter 502. An amplified firing current 46,762 then flows through projection 513 to fire emitter 516, whlch in turn provides symmetrically amplified firing of the main thyristor.
If the ratio of lengths of projections 508 and 513 is approximately 1:2 or larger, the auxiliary emitter 516 will fire before emitter 510. Emitter 510 then acts as a current amplifier ~ust during the turn-on delay phase, increasing the gate current density in emitter 516 before turn-on. Emitter 510 will thus not have to carry a current with high current density after the device has turned on.
Variations of the above-described preferred embod-iments will readily occur to those skilled in the art. For example, an etched depression or moat can replace the bal-last segment. However, these and other variations of struc-ture to achieve equivalent functions are contemplated to be within the scope of the appended claims.
' : ' ' "
Field of the Invention The present invention pertains to light activated semiconductor switching devices, and particularly to thyris-tors which can be fired by a light-emitting diode.
Descri~tion of the Prior Art , An important design criterion of light activated thyristors is the ability to be fired (triggered) by means of a low intensity radiation source, as for example, a light-emitting diode (LED). A disadvantage associated with suchuse of LED's to fire thyristors is the relatively low density of carriers generated in the semiconductor body, which re-sults in a slow firing rate. It is known that slow firing causes hot-spots in the semiconductor body due to high load current densities localized at random points where initial .
-~F
46,762 conduction sets in, thereby damaging the thyristor. The present invention, therefore, is addressed to the problem of making a light activated thyristor which responds more effectively to a low intensity radiation source.
Prior art thyristors are provided with base-emitter short circuits (shunts), which improve dv/dt response. Un- ~
fortunately, the shunts also drain off the light-generated -carriers by providing low impedance paths to the emitter electrode directly from the area in the base where the car-10 riers are generated. While it is true that a reduction in ;~
base-emitter shunting increases the current density of light-generated carriers passing through the base-emitter PN ~unc-tion, such a reduction in shunting also adversely affects the dv/dt response. Thus, those skilled in the art will recognize that a reduction in shunting is an impractical trade-off, and that a means of increasing the current density of light-generated carriers crossing the base-emitter PN ~unction is required, while at the same time maintaining adequate shunt-ing.
SUMMARY OF THE INVENTION
In accordance with the present invention, a light-activated thyristor, which has an improved firing rate in response to low intensity radiation, comprises means provid-ing a low resistance path from a source area of light-generated carriers to a portion of a PN ~unction ad~acent to the source area, whereby the current density of carriers crossing the PN
junction is sufficient to fire the thyristor at the improved rate.
In one preferred embodiment, the low resistance path means comprises a gate electrode disposed between the source 46,762 -1C~64~50 area and the PN ~unction, the gate electrode having a pro-~ection bordering from about one fourth to about one half the length of the PN junction.
In another embodiment, the low resistance path means comprises a ballast segment disposed between the source area and the PN junction, the ballast segment hav-ing an opening bordering from about one fourth to about one half the length of the PN junction.
In still another embodiment, the low resistance path means comprises a ballast segment disposed between the source area and the PN junction, and a gate electrode in juxtaposition over the ballast segment, the ballast segment having an opening, the gate electrode having a projection in juxtaposition over the opening, the proJection bordering from about one fourth to about one half the length of the !
PN junction.
In a further embodiment, the low resistance path means comprises a closed-loop ballast segment surrounding the source area, and a gate electrode in ~uxtaposition over the ballast segment, the gate electrode having a projection overlapping the ballast segment, the pro~ection bordering from about one fourth to about one half the length of the PN ~unction.
BRIEF DESCRIPTION OF THE ~RAWINGS
Figures 1 and 2 are respectively a partial cross-section and a partial plan view of a first preferred embodi-ment of the present invention;
Flgures 3 and 4 are respectively a partial cross-section and a partial plan view of a second embodiment of the present invention;
46,762 SO
Figure 5 is a plan view of a third embodlment of the present invention;
Figure 6 is a plan view of a fourth embodiment of the present invention; and, Figure 7 is a plan view of an embodiment of the present invention having an auxiliary thyristor.
DESCRIPTION OF THE PR~FERRED EMBODIMENT
Referring to Figures 1 and 2, a portion of a light , activated thyristor 100 illustrates a first preferred embod-iment of the invention. The thyristor 100 comprises a body 101 of semiconductor material typically having four zones of alternate conductivity type produced in a known manner, only three of which are explicitly shown for ease of illustration.
An emitter zone 102 of a first conductivity type is situated in body 101 ad~acent to a top major surface of the body 101.
A base zone 103 of a second conductivity type is situated beneath emitter zone 102. An interior zone 104 of the first conductivity type is situated beneath the base zone 103.
There is at least one additional zone (not shown) situated beneath zone 104, such as an anode zone of the second con-ductivity type bordering a bottom major surface (not shown) of the body 101. An emitter electrode 105 is affixed to the body 101 contacting the emitter zone 102 and small shunt por-tions 106 of the base zone 103, the shunts 106 providing base-emitter short circuits known in the art. A gate electrode 107 is affixed to the body 101 contacting the base zone 103 as shown. The gate electrode 107 takes the shape of a closed-loop or annulus having a projection 108 extending outward.
The gate electrode 107 encompasses a portion 109 of the top major surface above the base zone 103, which constitutes a - 46,762 ~ ~ 4~50 source area of llght-generated carriers. Associated with the thyristor 100 ls a means (designated by the superimposed arrows) for illuminating the base zone 103 with low intensity radiation, comprising for example a LED. Interfacing base zone 103 and emitter zone 102 is a PN junction 110, which preferably ~orms a closed-loop at its intersection with the top ma~or surface of body 101, thereby circumscribing the gate electrode 107 and the carrier source area 109 therein.
The pr,o~ection 108 borders a fractional portion of the closed-loop of the PN ~unction 110, the separation distance betweenthe projection 108 and the PN junction 110 being uniform as shown.
When source area 109 is illuminated with low in-tensity radiation, pairs of charge carriers are produced in the base zone 103 within the annular gate electrode 107.
Carriers of one polarity travel to the electrode 107, which causes a current to flow through the pro~ection 108 into the narrow strip of base zone 103 between the pro~ection 108 and the PN ~unction 110. The current density is thereby concen-trated by the shape of the electrode 107. The concentrated - current then flows through PN ~unction 110 into emitter zone 102 and from there into emitter electrode 105. Pro~ection 108, being metallic, provides a low resistance path relative to the semiconductor material of base zone 103 surrounding the electrode 107. Consequently, most of the light-generated current flows via pro~ection 108 through PN ~unction 110.
Furthermore, since the pro;ection 108 borders a fractional portion of the length of the surrounding PN ~unction 110, the current density through the PN ~unction 110 is sufficient to fire the thyristor 100 at a rate faster than a similar prior 46,762 ~ 5 O
art device without the projection 108. Thus, the incidence of load current hot-spotting found in slower prior art de-vices is substantially reduced in thyristors of the present invention. The fractional portion of the length of the PN
~unction 110 bordered by projection 108 should be less than one half the total length of the intersection of PN ~unction 110 with the surface of body 101 along a line immediately surrounding the gate electrode 107. Preferably, however, pro~ection 108 borders about one fourth such length of PN
~unction 110 at the surface.
When thyristor 100 is operating under load condi-tions, emltter e]ectrode 105 is connected to an external cir-cuit while gate electrode 107 remains free floating. There-fore, any changes in circuit voltage (dv/dt) are impressed on thyristor 100 at emitter electrode 105. Semiconductor body 101 has a capacitance which results in a current in the presence of a dv/dt. As shown by the arrowpaths in Figure 1, such dv/dt current, as long as it does not lead to turn-on, flows upward into base zone 103 and then essentially symmet-rically radially outward and through shunts 106 to the emitterelectrode 105. The pro~ection 108 has in this case no influ-ence on the current distribution. Only when the dv/dt-current becomes so high that the current fraction flowing into emitter 110 will reach the same order of magnitude as that flowing into the shunts 106, will the current begin to flow preferably through pro~ection 108. Thus for very high dv/dt thyristor 100 has a somewhat increased sensitivity to dv/dt firing in comparison to prior art thyristors.
Now referring to Figures 3 and 4, wherein similar 3 numerals designate similar parts, a thyristor 200 is shown :: :
46,762 16~ 50 which has an alternate means for providing a low resistance path for light~generated carriers. A relatively low resis-tance path is created by increasing the resistance around source area 209 by means of a ballast segment 211 of the same conductivity type as emitter zone 202. As seen in Figure 4, ballast segment 211 is C-shaped, which provldes an opening as a low resistance path means from the source area 209 to the PN junction 210. Preferably the ballast segment 211 sur-rounds most of the source area 209, such that the opening borders about one fourth of the length of the PN junction 210 surrounding the ballast segment 211. Ballast segment 211 can be formed by known masking techniques simultaneously with the diffusion of emitter zone 202.
The functioning of thyristor 200 is analogous to that of thyristor 100. When source area 209 is illuminated with low intensity radiation, carriers are generated which flow via the relatively low resistance path of the opening in ballast segment 211 through the portion of PN junction 210 bordering the opening. The current density is thereby concentrated in the low resistance path causing firing to occur at an improved rate similarly as described above.
Now referring to Figure 5, similar numerals desig-nating similar parts, a thyristor 300 is shown which essen-tially combines both low resistance path means of thyristors 100 and 200. Gate electrode 307 lies in juxtaposition over ballast segment 311, such that gate electrode 307 overlaps the inner portion of ballast segment 311 and the ad~acent source area 209 disposed within the ballast segment 311 as shown. Projection 308 lies in juxtaposition over an opening in the ballast segment 311.
46,762 ` 1~64150 Now referring to Fig~re 6, similar numerals desig-nating similar parts, a thyristor 400 is shown which is a slight structural modification of thyristor 300 of Figure 5. -Thyristor 400 of Figure 6 has a closed-loop ballast segment 412 surrounding source area 409. Gate electrode 407 lies in ~uxtaposition over ballast segment 412, gate electrode 407 having a projection 408 overlapping the ballast segment 412 to provide a low resistance path from source area 409 to a portion of PN ~unction 410 bordering the pro~ection 408.
Now referring to Figure 7, similar numerals desig-nating similar parts, a thyristor 500 is shown which incor-porates by way of example the low resistance path means of thyristor 300 into a thyristor structure having a so-called amplifying gate structure or integrated auxiliary thyristor structure. Thyristors with amplifying gates are known in the art. It is to be understood that any one of the embodiments described above can be successfully combined with an ampli-fying gate thyristor. In particular, thyristor 500 comprises a secondary emitter electrode 505 affixed to secondary emitter zone 502, and an amplifying gate electrode 515 affixed to an auxiliary emitter zone 516. The amplifying gate electrode 515 fires the main thyristor (not shown) in a known manner.
The electrode 505 has a projection 513 extending from zone 502 into the base zone 503 thereby bordering PN ~unction 514.
The projection 513 iS symmetrically disposed radially outward from pro~ection 508, but could also be positioned at any angle.
When thyristor 500 is forward biased and source area 509 is illuminated with low intensity radiation, carriers are generated which flow via pro~ection 508 through PN ~unction 3Q 510 thereby firing emitter 502. An amplified firing current 46,762 then flows through projection 513 to fire emitter 516, whlch in turn provides symmetrically amplified firing of the main thyristor.
If the ratio of lengths of projections 508 and 513 is approximately 1:2 or larger, the auxiliary emitter 516 will fire before emitter 510. Emitter 510 then acts as a current amplifier ~ust during the turn-on delay phase, increasing the gate current density in emitter 516 before turn-on. Emitter 510 will thus not have to carry a current with high current density after the device has turned on.
Variations of the above-described preferred embod-iments will readily occur to those skilled in the art. For example, an etched depression or moat can replace the bal-last segment. However, these and other variations of struc-ture to achieve equivalent functions are contemplated to be within the scope of the appended claims.
' : ' ' "
Claims (7)
1. A light activated thyristor comprising:
a) a body of a semiconductor material; said body comprising an emitter zone of a first conductivity type ad-jacent to a major surface of said body, a base zone of a second conductivity type adjacent to said emitter zone and sharing a portion of said major surface with said emitter zone, a PN junction interfacing said base zone and said emitter zone, said PN junction intersecting said major sur-face, said base zone having an area for receiving low inten-sity radiation, said area being a source of carriers gener-ated by said radiation; and, b) means providing a low resistance path for carriers in said source area to said PN junction, such that radiation-generated carriers in said source area are con-centrated in said path while flowing to said PN junction.
a) a body of a semiconductor material; said body comprising an emitter zone of a first conductivity type ad-jacent to a major surface of said body, a base zone of a second conductivity type adjacent to said emitter zone and sharing a portion of said major surface with said emitter zone, a PN junction interfacing said base zone and said emitter zone, said PN junction intersecting said major sur-face, said base zone having an area for receiving low inten-sity radiation, said area being a source of carriers gener-ated by said radiation; and, b) means providing a low resistance path for carriers in said source area to said PN junction, such that radiation-generated carriers in said source area are con-centrated in said path while flowing to said PN junction.
2. The thyristor of claim 1 wherein said low resistance path means comprises a gate electrode disposed between said source area and said PN junction, said gate electrode having a projection bordering from about one fourth to about one half the length of said PN junction intersection with said major surface.
3. The thyristor of claim 1 wherein said low resistance path means comprises a ballast segment disposed between said source area and said PN junction, said ballast segment having an opening bordering from about one fourth to about one half the length of said PN junction intersection with said major surface.
4. The thyristor of claim 1 wherein said low resistance path means comprises a ballast segment disposed between said source area and said PN junction, and a gate electrode in juxtaposition over the ballast segment, said ballast segment having an opening, said gate electrode hav-ing a projection in juxtaposition over said opening, said projection bordering from about one fourth to about one half the length of said PN junction intersection with said major surface.
5. The thyristor of claim 1 wherein said low resistance path means comprises a closed-loop ballast seg-ment surrounding the source area, and a gate electrode in juxtaposition over said ballast segment, said gate electrode having a projection overlapping said ballast segment, said projection bordering from about one fourth to about one half the length of said PN junction intersection with said major surface.
6. The thyristor of claim 1 further comprising means for amplifying a firing current from said emitter zone to a larger surrounding emitter zone.
7. The thyristor of claim 6 wherein said ampli-fying means comprises an outer metallic projection symmetri-cally disposed radially from an inner metallic projection, said outer projection length is about twice said inner pro-jection length.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2538549A DE2538549C2 (en) | 1975-08-29 | 1975-08-29 | Thyristor controllable with light |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1064150A true CA1064150A (en) | 1979-10-09 |
Family
ID=5955165
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA259,920A Expired CA1064150A (en) | 1975-08-29 | 1976-08-26 | Light activated thyristor |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4060826A (en) |
| JP (1) | JPS5229189A (en) |
| CA (1) | CA1064150A (en) |
| DE (1) | DE2538549C2 (en) |
| FR (1) | FR2322458A1 (en) |
| GB (1) | GB1544495A (en) |
| SE (1) | SE420874B (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4047219A (en) * | 1975-11-03 | 1977-09-06 | General Electric Company | Radiation sensitive thyristor structure with isolated detector |
| CH614811A5 (en) * | 1977-04-15 | 1979-12-14 | Bbc Brown Boveri & Cie | Thyristor |
| SU793421A3 (en) * | 1976-06-02 | 1980-12-30 | Ббц Аг Браун | Photothyristor |
| DE2725265A1 (en) * | 1976-06-04 | 1977-12-08 | Tokyo Shibaura Electric Co | SEMI-CONDUCTOR LIGHT DISPLAY DEVICE |
| US4219833A (en) * | 1978-05-22 | 1980-08-26 | Electric Power Research Institute, Inc. | Multigate light fired thyristor and method |
| US4207583A (en) * | 1978-07-27 | 1980-06-10 | Electric Power Research Institute, Inc. | Multiple gated light fired thyristor with non-critical light pipe coupling |
| US4186409A (en) * | 1978-08-11 | 1980-01-29 | Westinghouse Electric Corp. | Light activated silicon switch |
| JPS57192075A (en) * | 1981-05-20 | 1982-11-26 | Fuji Electric Corp Res & Dev Ltd | Photo trigger thyristor |
| JPS57196568A (en) * | 1981-05-27 | 1982-12-02 | Fuji Electric Corp Res & Dev Ltd | Photo trigger thyristor |
| JPS58101460A (en) * | 1981-12-11 | 1983-06-16 | Mitsubishi Electric Corp | Photo trigger thyristor |
| DE3374740D1 (en) * | 1982-11-15 | 1988-01-07 | Toshiba Kk | Radiation-controllable thyristor |
| JPS6064469A (en) * | 1983-09-19 | 1985-04-13 | Hitachi Ltd | Photo thyristor |
| EP0304032B1 (en) * | 1987-08-20 | 1993-01-27 | Siemens Aktiengesellschaft | Light controlled thyristor |
| US6154477A (en) * | 1997-05-13 | 2000-11-28 | Berkeley Research Associates, Inc. | On-board laser-triggered multi-layer semiconductor power switch |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3489962A (en) * | 1966-12-19 | 1970-01-13 | Gen Electric | Semiconductor switching device with emitter gate |
| SE352779B (en) * | 1967-12-28 | 1973-01-08 | Asea Ab | |
| FR2050630A5 (en) * | 1969-06-19 | 1971-04-02 | V Elektrotekhni | |
| US3731162A (en) * | 1969-09-25 | 1973-05-01 | Tokyo Shibaura Electric Co | Semiconductor switching device |
| JPS508315B1 (en) * | 1970-02-20 | 1975-04-03 | ||
| DE2300754A1 (en) * | 1973-01-08 | 1974-07-11 | Siemens Ag | THYRISTOR |
| DE2346237A1 (en) * | 1973-09-13 | 1975-03-27 | Siemens Ag | THYRISTOR |
| DE2346256C3 (en) * | 1973-09-13 | 1981-11-05 | Siemens AG, 1000 Berlin und 8000 München | Thyristor |
| US3893153A (en) * | 1974-01-10 | 1975-07-01 | Westinghouse Electric Corp | Light activated thyristor with high di/dt capability |
| JPS50123282A (en) * | 1974-03-15 | 1975-09-27 | ||
| US4012761A (en) * | 1976-04-19 | 1977-03-15 | General Electric Company | Self-protected semiconductor device |
-
1975
- 1975-08-29 DE DE2538549A patent/DE2538549C2/en not_active Expired
-
1976
- 1976-08-02 US US05/710,972 patent/US4060826A/en not_active Expired - Lifetime
- 1976-08-05 GB GB32610/76A patent/GB1544495A/en not_active Expired
- 1976-08-23 SE SE7609343A patent/SE420874B/en unknown
- 1976-08-26 CA CA259,920A patent/CA1064150A/en not_active Expired
- 1976-08-26 JP JP51102154A patent/JPS5229189A/en active Pending
- 1976-08-27 FR FR7625978A patent/FR2322458A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE2538549A1 (en) | 1977-03-03 |
| DE2538549C2 (en) | 1985-06-13 |
| US4060826A (en) | 1977-11-29 |
| GB1544495A (en) | 1979-04-19 |
| FR2322458B1 (en) | 1982-10-22 |
| JPS5229189A (en) | 1977-03-04 |
| SE7609343L (en) | 1977-03-01 |
| SE420874B (en) | 1981-11-02 |
| FR2322458A1 (en) | 1977-03-25 |
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