Deep states and misfit dislocations in indium-doped GaAs layers grown by molecular beam epitaxy

We have studied the effects of adding small amounts of indium (0.6 at. %) in GaAs layers grown by molecular beam epitaxy on GaAs substrates. Photoluminescence spectra showed that epilayers of high crystal quality were obtained, and electron beam induced current microscopy revealed a number of misfit dislocations near the interface and a dislocation-free zone near the top surface. We observed several well known deep traps in the dislocation-free zone, albeit at much lower concentrations in comparison to indium-free, otherwise identical epilayers. We failed to observe any traps in the misfit dislocation zone. If, as is widely held, we assume that these traps are due to point defects and their complexes, a possible explanation of the absence of traps in the dislocation zone is that the traps provide the point defects necessary for the creation and climb of the misfit dislocations.