Photolumineseence investigation of ingot- and wafer-annealing effects on semi-insulating GaAs

Photoluminescence spectroscopy is used to characterize semi-insulating Czochralski-grown GaAs. The spectra show the differences induced by the different post growth annealing procedures, i.e. ingot- or wafer-annealing, single- or multi-step. The wafer annealing techniques definitely lead to an improvement of the crystalline quality, while ingot annealed crystals present additional defect related-emissions. For multi-step ingot-annealed crystals, two transitions around 1.45 eV are identified with the (e,A/spl ring/) and the (D/spl ring/,A/spl ring/) recombinations of an acceptor-like defect, different from the 78-meV double acceptor. On the other hand, wafer-annealed crystals present much lower concentrations of background impurities, as estimated by selective pair luminescence.