Surface effect-induced fast Be diffusion in heavily doped GaAs grown by molecular-beam epitaxy

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Abstract
Van der Pauw measurements, C-V measurement, and secondary ion mass spectrometry were used to study the rapid diffusion of Be in heavily doped GaAs epilayers grown by MBE. The concentration dependence of the Be diffusion was measured. A discrepancy exists at high doping level between our experimental results and the Be interstitial-substitutional diffusion model previously proposed. The threshold of fast Be diffusion versus doping concentration was determined and a diffusion coefficient as high as 2×10−12 cm2/s was observed at 600 °C. A surface Fermi-level pinning effect model has been proposed in addition to the interstitial-substitutional model, which has successfully explained the onset of fast Be diffusion in MBE-grown GaAs at high doping level.