Effects of the growth temperature and As/Ga flux ratio on the incorporation of excess As into low temperature grown GaAs

The controlled incorporation of excess As into GaAs grown by molecular beam epitaxy at low growth temperatures (LT-GaAs) is explored. The substrate temperature and the As/Ga flux ratio were systematically varied to investigate the influence of growth parameters on the formation of native defects and structural properties. Near infrared absorption, magnetic circular dichroism of absorption, and slow positron annihilation were applied to determine point defect concentrations of As antisites ${\mathrm{(As}}_{\mathrm{Ga}})$ and Ga vacancies ${\mathrm{(V}}_{\mathrm{Ga}}\mathrm{).}$ Structural properties of as-grown and annealed LT-GaAs layers were investigated by x-ray diffraction and transmission electron microscopy. In a well defined parameter range the lattice expansion of the LT-GaAs layers correlates with the amount of ${\mathrm{As}}_{\mathrm{Ga}}.$ The $V_{\mathrm{Ga}}$ acceptor concentration can quantitatively account for the ionization of the ${\mathrm{As}}_{\mathrm{Ga}}$ donors.