Resonant-cavity avalanche photodiodes and narrow spectral response photodiodes

High speeds, high external quantum efficiencies, narrow spectral linewidths, and convenience in coupling make resonant-cavity photodetectors (RECAPs) good candidates for telecommunication applications. In this paper, we report a highly-efficient and wavelength-selective separate absorption and multiplication (SAM) avalanche photodiode (APD) with a thin (500 Å) absorbing layer. The improved characteristics of the photodetector were obtained by placing the absorption and multiplication layers in a Fabry-Perot cavity. An external quantum efficiency of 77% was achieved with a spectral linewidth of less than 4 nm and an avalanche gain of more than 50. We also present the experimental results on a RECAP having an operating wavelength λ₀≈1.3 μm with a very narrow spectral response. The absorption takes place in a thin In_0.53Ga_0.47As layer placed in an InP cavity. The InP p-i-n structure was wafer bonded to a high-reflectivity GaAs-AlAs quarter-wavelength Bragg reflector. The top mirror consisted of three pairs of a ZnSe-CaF₂ quarter-wavelength stack (QWS). A spectral linewidth of 1.8 nm was obtained with an external quantum efficiency of 48%