Diffusion kinetics of Si in GaAs and related defect chemistry

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Abstract
The diffusion of Si in GaAs was investigated using diffusion sources from different tie triangle regions on the Si-Ga-As ternary phase diagram which provide constant chemical potentials for the three components under isothermal conditions. The Si profiles are measured with secondary ion mass spectrometry and differ significantly for the different sources. The Ga-Si-GaAs tie triangle source produces p-type Si doping with concentration independent diffusion coefficients, and a neutral As or Ga vacancy is proposed as the dominant mobile defect for these conditions. Arsenic-rich sources from two tie triangle regions and also a Si-GaAs tie line source produce Si donor diffusion with concentration-dependent diffusion behavior. The concentration-dependent diffusion coefficients of donor Si for As-rich source diffusion are related to the net ionized donor concentration showing three different regimes: intrinsic regime, intermediate regime, and saturation regime. Ga vacancies are proposed to be responsible for donor Si diffusion in GaAs: a V0Ga and/or V−Ga mechanism for the intrinsic regime; and a V−Ga related mechanism for the extrinsic and saturation regimes. The Si-GaAs tie line source resulted in two branch type profiles, intermediate between the As-rich and the Ga-rich source diffusion cases.