Does beryllium doping suppress the formation of Ga vacancies in nonstoichiometric GaAs layers grown at low temperatures?

We investigate native defects in nonstoichiometric GaAs layers grown at low temperatures by molecular-beam epitaxy (LT-GaAs) doped with Be. Ga vacancies (VGa) are found by positron annihilation in all layers. The concentration of VGa is independent of the Be doping in contrast to the previous belief that it decreases. Simultaneously, the concentration of As antisite defects (AsGa) was measured by optical absorption. We find the same relationship between VGa and AsGa concentrations as reported earlier for undoped LT-GaAs. Thus, Be doping has no significant influence on the incorporation of native point defects in LT-GaAs. The thermal stability of such material must therefore be explained otherwise.