Anomalies in annealed LT-GaAs samples

Abstract

The annealing behavior of low temperature (LT)-GaAs layers was investigated using transmission electron microscopy, x-ray rocking curves, and H⁺ ion channeling. These data were compared to the Hall-effect and conductivity data obtained earlier on the same samples. An expansion of the lattice parameter above those observed for as-grown LT-GaAs layers was observed for the layers annealed at 300 and 350°C. No precipitation was observed in transmission electron micrographs for these annealing temperatures. Based on ion-channeling results, the As atoms (split interstitials) appear to be in the same position as found for the as-grown layers. A special arrangement of As split interstitials or out-annealing of gallium vacancies would be consistent with a decrease of the dominant acceptor in these layers and an increase in the lattice parameter. For annealing above 400°C, the lattice parameter decreased and in fact was found to achieve the substrate value at annealing temperatures of 500°C and above. The decrease in the lattice parameter above 400°C is related to the decrease of excess As antisite defects and As split interstitials in the formation of As precipitates.