Annealing properties of Si-atomic-layer-doped GaAs

Si-atomic-layer-doped GaAs layers are grown at 520°C by flow-rate modulation epitaxy using a 1-s silane pulse. Carrier profiles are measured by the capacitance-voltage method before and after annealing at 700, 800, and 900°C. The sheet carrier concentration increases with the silane mole fraction, and saturates at about 3×10¹² cm^-2. The samples with saturated sheet carrier concentrations exhibit a distinct plateau at the top of the carrier concentration profile after annealing, while the samples with unsaturated sheet carrier concentrations show normal Gaussian-like broadening. The peak carrier concentration at the plateau of the annealed sample is found to be sensitive to annealing temperature, indicating that the carrier concentration is controlled by some thermodynamic limitation.