InGaP/AlGaAs Near-UV and Visible Avalanche Photodiodes for Li-Fi Application

In this work, we demonstrate two InGaP/AlGaAs heterojunction avalanche photodiodes with Al component of 0.8 and 0.6 for Li-Fi applications in near-UV and visible light bands. The devices exhibit high multiplication gain, low dark current, and low excess noise factor. By incorporating an InGaP p-layer with a low recombination velocity, we overcome the issue of low UV and near-UV response caused by the high surface recombination of GaAs and AlGaAs materials. The
${Al_{0.8}Ga_{0.2}As}$
device with a recessed window showed an external quantum efficiency (EQE) of 13.12% at 355 nm and 27.12% at 405 nm, with a peak EQE of 38.72% at 440 nm. The
${Al_{0.6}Ga_{0.4}As}$
device exhibits a peak EQE of 43.55% at 540 nm. Furthermore, the photodiodes demonstrate a 3 dB bandwidth of up to 1.59 GHz at 405 nm and 1.12GHz at 520 nm at 99% breakdown voltage. This indicates their future potential for applications in short-distance visible and near-UV light communications.