High-frequency InP/InGaAs pin photodiodes with efficient response at short wavelengths

It is shown that InP-based pin photodiodes can be operated at high frequency with high quantum efficiency over a broad range of wavelengths (0.6-1.6 mu m). Good window layers for high-speed detectors can be made with n/sup ++/ InP for two reasons: the high carrier concentration enables low sheet resistance to be obtained with very thin layers, and the Burstein-Moss effect significantly reduces the absorption coefficient of the layer in the lambda =0.7-0.9 mu m range. This provides a low-resistance cap layer that is highly transparent over the lambda =0.7-1.6 mu m range and is lattice-matched to the InGaAs(P) active layer. At lambda =0.86 mu m, the detectors demonstrate a flat heterodyne response up to 3 GHz, with 3-dB roll-off of 8 GHz and DC quantum efficiency of approximately 80%. Their current-carrying capability makes them attractive for use in systems that require high local-oscillator power. The detectors are well suited for use with all the semiconductor laser sources available the traditional AlGaAs/GaAs and InP/InGaAsP as well as the new, strained-layer, quantum-well InGaAs/AlGaAs/GaAs and InGaAs/InGaP/GaAs lasers.<>