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 anni hilation spectroscopy. Positron trapping at both gallium vacancy (V-Ga) and antisite (Ga-As) defects were found to increase after the in-diffusion, an d increase further after the out-diffusion of Li. This indicates an increas e in the concentrations of negative and neutral defects in both phases. Maj ority of the Ga vacancy and antisite defects is, however, supposed to be fo rmed 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 th e incorporation of Li. All these results can be explained by a simple set o f defect formation and reduction processes. (C) 1999 Elsevier Science B.V. All rights reserved.