Influence of the substrate orientation on Ge incorporation in molecular-beam epitaxial GaAs

The incorporation of Ge in GaAs layers grown simultaneously on (100), (311)A, and (311)B GaAs substrates by molecular-beam epitaxy has been studied using Hall-effect measurements, photothermal ionization spectroscopy, and photoluminescence. The quantitative analysis shows that Ge is more amphoteric than Si, but the orientation dependence of the amphoteric behavior of Ge is similar to Si. The amphoteric site preference of Ge is more selective for growth on the (311) polar orientation than on the (100) nonpolar orientation. Like Si, Ge incorporates predominantly as a donor in (311)B growth, while it incorporates predominantly as an acceptor in (311)A growth.