Photoluminescence of molecular beam epitaxially grown Ge‐doped GaAs

The role played by molecular beam epitaxial growth conditions in Ge‐doped GaAs and the introduction of deep levels inside the forbidden gap were investigated by means of photoluminescence. Firstly, a qualitative correlation was established between the compensation ratio obtained from Hall measurements and the ratio between the integrated intensity of the conduction band–acceptor transition to that of the donor–valence band. Secondly, two peaks at 1.41 and 1.45 eV, very similar to those introduced by another amphoteric impurity (Si) and systematically found in nearly all the samples, were studied in order to clarify their origin. GeAs appears to be involved in both cases. The intensity of the 1.45 eV line increases with growth temperature which agrees with the assignment to a GeAs–VAs complex already suggested elsewhere. Conversely, the emission intensity at 1.41 eV decreases strongly with increasing growth temperature and the presence of GeAs–Asi and/or GeAs–AsGa complexes is suggested to explain this result.