Effect of As overpressure on Si-doped (111)A GaAs grown by molecular beam epitaxy: a photoluminescence study

The authors report on a photoluminescence investigation of heavily Si-doped (111)A-oriented GaAs samples. Molecular beam epitaxial growth has been performed with different As overpressures. The increase of the As pressure induces a site switching of Si from an As site (where Si is an acceptor) to a Ga site (where Si is a donor). This conversion from p- to n-type coincides with a change in the main point defect present in the sample: As vacancy (V_As) for low As pressure and Ga vacancy (V_Ga) for high As pressure. The authors suggest that their relative equilibrium is given by V_As to or from V_Ga+Ga_As, where Ga_As is a gallium antisite, and that by increasing the As pressure this reaction is moved to the left.