A sapphire substrate, a buffer layer of undoped GaN and a compound semiconductor crystal layer successively formed on the sapphire substrate together form a substrate of a light emitting diode. A first cladding layer of n-type GaN, an active layer of undoped In0.2Ga0.8N and a second cladding layer successively...http://www.google.com/patents/US6593159?utm_source=gb-gplus-sharePatent US6593159 - Semiconductor substrate, semiconductor device and method of manufacturing the same
