High-speed polysilicon resonant-cavity photodiode with SiO2-Si Bragg reflectors

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. In this letter, we report an interdigitated p-i-n polysilicon resonant-cavity photodiode, which employs a Si-SiO2 Bragg reflector, that is more compatible with standard Si processing technology, For an absorbing region thickness of only 0.5 mu m, a peak quantum efficiency of 40% was achieved and the dark current was <60 nA at 10 V, For 2 mu m x 2-mu m finger width and spacing the bandwidth was 10 GHz.