EVIDENCE FOR A VACANCY-RELATED GROUND-STATE OF THE DX CENTER IN ALXGA1-XSB - A POSITRON-ANNIHILATION STUDY

A vacancy-related defect center is observed by positron annihilation in AlxGa1-xSb (x = 0.5). This center appears at a concentration that is equal to the DX-center concentration observed by deep-level transient spectroscopy (DLTS). At low temperatures, the vacancy exhibits a metastable behavior after light illumination. The recovery kinetics of this center agrees with the established properties of the DX center with an activation energy of E(a) = (85 +/- 10) meV. In agreement with theoretical predictions, it was concluded that the vacancy is part of the ground state of the DX center. The results are in line with DLTS, the Hall effect, and photoconductivity experiments.