The origin of the 1.356 eV emission band measured by photoluminescence (PL) is investigated by correlating the Hall measurement data for the same materials. The crystals grown by the horizontal-Bridgman technique were As or Ga rich by controlling As-zone temperatures. Type conversion from n to p type with the thermal activation energy ΔE=0.133 eV and ΔE=0.05 eV were achieved by heat treatment of the As-rich crystals. The Ev +0.133 eV level and the 1.356 eV band may not be attributed to the same defect because the Ev +0.133 eV level is electrically active with a nonradiative center and the 1.356 eV band is radiative with an electrically inactive (neutral) center. Therefore, both Ev +0.133 eV level and the 1.356 eV band were not attributed to copper impurity because copper is electrically and optically an active center in GaAs. The 1.356 eV band measured by PL may be due to a gallium-vacancy related complex, but differs from VGa -donor complex.
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