Nonequilibrium carrier distribution in semiconductor photodetectors: Surface leakage channel under illumination

摘要

The nonequilibrium carrier distribution in an InGaAs/InP avalanche photodiode under light illumination is obtained by cross-sectional scanning capacitance microscopy combined with numerical simulation. The sheet density of negative surface charge is determined to be 1.85×1010 cm-2 on the native-oxidized InGaAs (110) face. This surface charge is found responsible for the accumulation of minority holes, which leads to an inversion layer at the sidewall surface of device in the absorption region under illumination exceeding 0.1 mW/cm2. The inversion depth increases up to 200 nm along with the enhancement of excitation intensity. This work suggests that a surface leakage channel may form in semiconductor photodetectors through detection light excitation.