Radio-frequency molecular-beam-epitaxy growth of III nitrides for microsensor applications

To date, GaN-based compounds have proven commercially viable for optoelectr onic devices such as light-emitting diodes (LEDs), laser diodes, and UV det ectors, and are also under investigation for use in high-power, high-temper ature electronics. Other areas in which the III nitrides could be especiall y beneficial are in high-energy particle detectors and in narrow-band optic al sensors for the UV/visible spectral range. In addition to the inherent t hermal, mechanical, and chemical stability of III nitrides, such devices wo uld benefit from the larger band gap, higher breakdown, and insulating prop erties of GaN and related alloys. The surface quality of nitride materials is generally good, and this is very important for fabrication of optical de vices. The specific characteristics of the Ill-nitride layers can be achiev ed by appropriate substrate selection and precise control over the material growth process. In this article. results on radio-frequency molecular-beam -epitaxy growth of GaN, AIN, AlGaN, and InGaN layers on sapphire and silico n substrates for optoelectronic sensor development applications are present ed. Growth of high-quality p-GaN layers with hole concentration of up to si milar to 5 x 10(17) cm(-3) were realized and used in Schottky barrier light -emitting and photodiode structures. AlGaN layers with an Al mole fraction up to 42% as measured by cathodoluminescence, and AIN layers with breakdown fields of 333 V/mum are currently being investigated for applications as i nsulating layers and active layers, respectively, for devices with an UV-ex tended spectral range such as hot-electron-based avalanche LEDs and photodi odes. (C) 2001 American Vacuum Society.