High-speed polysilicon resonant-cavity photodiode with SiO/sub 2/-Si Bragg reflectors

Abstract

Previously, it has been shown that the bandwidth of Si photodiodes can be increased by more than an order of magnitude, without sacrificing responsivity, by a resonant-cavity structure that utilized GeSi-Si asymmetric Bragg reflectors. We report an interdigitated p-i-n polysilicon resonant-cavity photodiode, which employs a Si-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Bragg reflector, that is more compatible with standard Si processing technology. For an absorbing region thickness of only 0.5 μm, a peak quantum efficiency of 40% was achieved and the dark current was <60 nA at 10 V. For 2 μm×2-μm finger width and spacing the bandwidth was 10 GHz.