Defects in as-grown and annealed AlxGa1−xAs single crystals

Photoluminescence studies were made on Sn-, Te- and Ge-doped Al_xGa_1-xAs 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_xGa_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-xAs 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_xGa_1-xAs: Ge. The exact nature of the defects giving rise to these bands is not known.