Effect of lithium diffusion on the native defects in GaAs studied by positron annihilation spectroscopy

The influence of Li diffusion on GaAs was studied by means of positron annihilation spectroscopy. Positron trapping at both gallium vacancy (V-Ga) and antisite (Ga-As) defects were found to increase after the in-diffusion, and increase further after the out-diffusion of Li. This indicates an increase in the concentrations of negative and neutral defects in both phases. Majority of the Ga vacancy and antisite defects is, however, supposed to be formed already during the in-diffusion phase at 800 degrees C, but to remain passivated by Li prior to the out-diffusion phase at 400 degrees C. The As antisite (EL2) and the As vacancy (V-As) defects were not detected after the incorporation of Li. All these results can be explained by a simple set of defect formation and reduction processes. (C) 1999 Elsevier Science B.V. All rights reserved.