Defects in as-grown and annealed Al xGa 1− xAs single crystals

Abstract

Photoluminescence studies were made on Sn-, Te- and Ge-doped Al x Ga 1- x As single crystals before and after annealing at 800°C for 21 h in evacuated and sealed quartz ampoules. The thin p-type surface layer, which was present on all nondegenerate n-Al x Ga 1- x As crystals after annealing, is attributed to the introduction of Si from the inner wall of the ampoule to form shallow Si As and V As-Si As acceptor defects. Sn As, V Ga-Te (or) V Al-Te), Ge As and V As-Ge As defects were observed in Sn-, Te- and Ge-doped Al x Ga 1- x As after annealing. The defects were identified by plotting their characteristic recombination radiation energies versus Al composition x and comparing with previously established assignments in GaAs ( x = 0). Two prominent bands, located at 1.53 and 1.46 eV independent of Al composition x, were detected in annealed (p) Al x Ga 1- x As: Ge. The exact nature of the defects giving rise to these bands is not known.