Uniform and delta doping of carbon in GaAs by solid-source molecular beam epitaxy using electron beam evaporation: Evidence for atomic pairing

Abstract

Uniform and delta-doped GaAs:C layers were grown by solid source molecular beam epitaxy (MBE) using electron-beam evaporation of the dopant. Uniform doping concentrations of up to 6×1019 cm−3 were measured and degradation of optical properties was noted when the hole concentration exceeded the mid-1018 cm−3 range. Delta-doping studies were carried out under various deposition conditions and an extremely high sheet carrier concentration of 9.6×1012 cm−2 was obtained under modulated beam condition. In contrast to carbon doping by resistively heated filament sources, all doping results were obtained with C1/C3 isomer ratios greater than unity. These findings show strong evidence for the identification of atomic carbon pairing as the dominant defect formation mechanism in heavily doped GaAs:C films prepared by solid source MBE.