Deep levels in semiconducting In-alloyed bulk n-GaAs and its resistivity conversions by thermal treatments

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Abstract
Thermal conversions of resistivities have been studied for In‐alloyed semiconducting (100–106 Ω cm) n‐GaAs grown by the liquid‐encapsulated Czochralski method. These dislocation‐free as‐grown crystals are converted into semi‐insulating (>107 Ω cm) crystals by annealing at 950 °C for 2 h followed by a fast cooling. Such semi‐insulating crystals can be converted further into crystals with lower resistivities (∼106 Ω cm) by treating them at 470 °C for 100 h. In the analysis of the as‐grown samples by the temperature‐dependent Hall measurements, four levels have been found with activation energies 0.13, 0.20, 0.42, and 0.50 eV. It has been shown that these resistivity conversions are induced by concentration changes of the deep states other than the midgap donor EL2, some of them being the levels found in this study.