HIGH-GAIN P-I-N INFRARED PHOTOSENSORS WITH BRAGG REFLECTORS ON AMORPHOUS SILICON-GERMANIUM ALLOY

An amorphous silicon-germanium alloy (alpha-SiGe:H) infrared photosens or with a Bragg reflector to obtain high optical gain and responsivity is demonstrated. The Bragg reflector containing cr-Si:H and alpha-SiG e:H layers was grown on the top of p-i-n structure with an amorphous s ilicon/germanium alloy. All of the amorphous silicon and amorphous sil icon-germanium layers were deposited by a low-temperature plasma enhan ced chemical vapor phase deposition system. The experimental results o f the new structures exhibit a much superior performance to that of co nventional p-i-n avalanche photosensor structures. That is, the struct ure 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 th e full width at half maximum can be reduced from 250 to 150 nm. (C) 19 97 American Institute of Physics.