Surface- and sidewall-damage of InP-based optoelectronic devices during reactive ion etching using CH4/H2

Systematic investigations are performed on the effect of reactive ion etching (RIE) using CH₄/H₂ based gases on InP based semiconductors. From rutherford backscattering analysis a strong dependence of crystalline damage on process parameters is found leading to a damaged region of less than 3 nm for an optimized process. Capacitance voltage profiling shows the effect of hydrogen channeling up to 0.5 μm deep into the semiconductor creating acceptor passivation which can be completely removed by annealing at low temperature. Using low temperature photoluminescence measurements on multiquantumwell structures, it is shown that the RIE process does not affect photoluminescence properties of quantum wells remarkably until the covering barrier is etched down to few nm. From these measurements a damage model of the etched semiconductor surface is presented. Sidewall damage of RIE etched InGaAs/InP Mesa-PIN-diodes is characterized by analyzing surface leakage currents. Furthermore, effects of different post-etch treatments on leakage currents are shown. By an optimized CH ₄/H₂/Ar-RIE process PIN-photodiodes are fabricated with dark current densities as low as 1.8×10^-5 A cm^-2 (bias voltage is -5 V) which are comparable to the best published wet etched Mesa-PIN-photodiodes