Low Temperature p- and n- Type Doping of InSb Grown on GaAs Using Molecular Beam Epitaxy.

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Abstract
30 nm thick layers of Be-doped InSb were grown by MBE, sandwiched between undoped layers of InSb on semi-insulating GaAs substrates. Using secondary ion mass spectroscopy (SIMS), it has been demonstrated that the p-type dopant, Be, undergoes an anomalous migration towards the top surface for substrate growth temperatures in excess of 340°C. A thermal diffusion process can be eliminated as an explanation since there was not an associated diffusion towards the substrate. At a substrate growth temperature of 340°C, the Be-doped layer had backside and frontside doping concentration gradients of 0.067 and 0.147 decade/nm. respectively. A sample grown at 420°C had a comparable backside doping concentration gradient, but the frontside gradient was essentially zero, i. e., uniform doping tothe surface. Electrical activation of the Be dopant, when grown at 340°C, compared to activation in GaAs grown at 580°C. was 38% and 47% for growth rates of 1.0 and 0.5 μm/h. While the Si dopant does not undergo a migration comparable to that of Be, it has been demonstrated that n-type doping of InSb with Si must be done at growth temperatures less than or equal to 340°C to obtain high carrier concentrations. The maximum n-type carrier concentration obtained was 6.2x1018/cm3, for a 0.5 μm/h growth rate at 340°C.