High-gain p-i-n infrared photosensors with Bragg reflectors on amorphous silicon-germanium alloy

An amorphous silicon-germanium alloy (alpha-SiGe:H) infrared photosensor with a Bragg reflector to obtain high optical gain and responsivity is demonstrated. The Bragg reflector containing cr-Si:H and alpha-SiGe:H layers was grown on the top of p-i-n structure with an amorphous silicon/germanium alloy. All of the amorphous silicon and amorphous silicon-germanium layers were deposited by a low-temperature plasma enhanced chemical vapor phase deposition system. The experimental results of the new structures exhibit a much superior performance to that of conventional p-i-n avalanche photosensor structures. That is, the structure with a Bragg reflector shows a significant improvement in optical gain from 80 to 328 under the incident optical power of 1 mu W, and the full width at half maximum can be reduced from 250 to 150 nm. (C) 1997 American Institute of Physics.