Behavior of excess As in nonstoichiometric Si-doped GaAs

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Abstract
The Si doping efficiency (≡[e−]/[Si]) in homoepitaxial GaAs has been measured as a function of molecular beam epitaxial growth conditions (As pressure, substrate temperature, and growth rate) and post‐growth thermal annealing conditions. The doping efficiency decreases from one under optimal growth conditions to almost zero: (1) exponentially with inverse substrate temperature below 400 °C and (2) as a power law in the As4‐to‐Ga beam‐equivalent fluence ratio above unity. The doping efficiency of nonoptimally grown films increases from almost zero to near one upon post‐growth thermal annealing above 650 °C with slower than exponential kinetics. These changes are attributed to charge trapping into and release from, respectively, excess‐As‐related defects, which are incorporated during growth and removed by out‐diffusion during annealing.