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Deep Level and Conduction Mechanism in Low-Temperature GaAs Grown by Molecular Beam Epitaxy

Deep levels in low-temperature (LT) GaAs layers grown by molecular beam epitaxy were investigated by deep level transient spectroscopy (DLTS), photocapacitance and photoluminescence (PL) techniques. Five electron traps were detected, for the first time, in Si-doped conductive LT-GaAs layers grown at 300–400°C. The dominant trap was found to be the S1 level with an activation energy of 0.64 eV and an electron capture cross section of σ n=2–4×10-14 cm2. The S1 level showed remarkable photoquenching behavior. No PL was observed from LT-layers. The mechanism responsible for the semi-insulating property of LT-GaAs layers is probably due to compensation by the S1 trap, which is not EL2 but a new electron trap peculiar to LT-GaAs layers.