Pair of local vibration mode absorption bands related to EL2 defects in semi-insulating GaAs

Abstract

A pair of correlated bands, which show the same fine structure at low temperature, is discovered in infrared absorption spectra of semi-insulating GaAs crystals. At 80 K the bands peak at 730 cm−1 and 714 cm−1, respectively. According to the fine structures, the spectral linewidths, and the temperature dependence of frequency shifts, the two absorption bands are identified to be induced by local vibration modes of the same defect. As the interconversion of the two bands under some conditions of illumination and temperature variation is very similar to the transformation between the ground state and the metastable state of the EL2 level, these absorptions are ascribed to be related to the EL2 defect.