Abstract
The positron two-dimensional angular correlation of annihilation radiation (2D-ACAR) technique has been coupled with optical excitation to study the native point defects in semi-insulating GaAs. The As vacancy was observed below \ensuremath{\sim}170 K when illuminated with 1.41\ifmmode\pm\else\textpm\fi{}0.07 eV photons. The temperature dependence of the 2D-ACAR spectra, with and without illumination, was studied. Data were also collected at 25 K as a function of the intensity of infrared light. The 2D-ACAR spectra reflect the ${\mathit{e}}^{+}$-${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ pair momentum distribution at or near the vacancy and provides symmetry and electronic structure information, which can be used as a unique defect signature for the vacancy.
Published Version
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