Depth dependence of silicon donor passivation and reactivation in hydrogenated GaAs

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Abstract
The depth dependence of silicon donor passivation and reaction in hydrogenated GaAs is directly determined for the first time by using 1000 Å layers of 1017 cm−3 Si-doped GaAs, buried at various depths in undoped GaAs. Low-frequency hydrogen plasma exposure for 30 min at 250 °C reduces the carrier density by only a factor of 3 in layers buried 3 μm deep, but by three orders of magnitude in layers buried 0.3 μm deep. Annealing at 400 °C for 5 min restores 100% of the original carrier density in the 3-μm-deep layer but only 73% in the 0.3-μm-deep layer. Plasma exposure and 400 °C annealing together do not improve the mobility in the molecular beam epitaxial samples at any depth. Hydrogen-related acceptors seen by photoluminescence account for these effects.