Hydrogen passivation of AlxGa1−xAs/GaAs studied by surface photovoltage spectroscopy

We study the effect of hydrogen passivation on Al x Ga 1− x As grown by liquid-phase epitaxy (LPE) on semi-insulating GaAs. Using surface photovoltage (SPV) spectroscopy and Hall measurements we investigate the effect of hydrogenation on Al x Ga 1− x As epilayers with electron concentrations in the range 10 16 –10 17 cm −3 . We measure the minority carrier diffusion length in the as-grown Al x Ga 1− x As epilayers to be in the range 0.1–0.8 μm and to increase significantly upon hydrogenation. Hydrogen passivation of interface states at the heterojunction is demonstrated for epilayers with low carrier concentration. We apply the result from the SPV measurements to speculate on the band bending at the heterojunction.