THE ALLOYING EFFECT ON POSITRON STATES IN SI1-XGEX

The effect of alloying on positrons in Si1-xGex is reported. Our compu tations are based on the independent particle model combined with the empirical pseudopotential method. To make an allowance for the chemica l disorder, the virtual crystal approximation is used, including a cor rection to the alloy potential. The evolution of the positron thermali zation energy versus mole fraction shows that the positrons diffuse be tter over the range 0.15 less than or equal to x less than or equal to 1.0. Our calculated positron effective band masses for Si and Ge an i n good agreement with the available experimental and theoretical ones, and vary non-linearly from Si to Ge. The positron distribution differ ence between different compositions indicates that the positron has an affinity for one sort of atom in Si1-xGex. It was noted that the posi tron is not sensitive to the disorder effect. Based on these results, this study could stimulate further work on the alloying effect on posi tron annihilation in semiconductor alloys. (C) 1998 Elsevier Science S .A. All rights reserved.