Far-infrared absorption due to shallow acceptors in semi-insulating GaAs in dependence on EL2 bleaching

摘要

Far-infrared absorption in semi-insulating GaAs due to electronic transitions of shallow acceptors was measured in dependence on conditions of bleaching the GaAs. intrinsic defect EL2. The far-infrared spectra were compared with the results of near-infrared spectroscopy of EL2 fundamental state. It was found that under conditions of low intensity illumination the neutral acceptors can coexist with the neutral EL2 defect. The model is proposed which explains the effects that were not observed previously, such as depopulation of neutral shallow acceptors at low temperature, and the charge redistribution between different shallow acceptor levels at increasing temperature for the samples co-doped with zinc and carbon. It is shown that far-infrared spectroscopy is suitable for quantitative evaluation of the shallow acceptor concentration in GaAs material. The corresponding calibration factors are given. [References: 18]