Evidence for highly localized states with a symmetry of substitutional donors which enter the gap of GaAs at high hydrostatic pressure

Abstract

For the first time a diamond anvil cell high-pressure technique has been used for far-infrared laser magneto-optical experiments. A shallow-deep transition was observed for shallow sulphur and silicon donors in high-purity GaAs at pressures of 25 and 30 kbar respectively. This transition is similar to that previously observed at 9 kbar for Ge residual donors. The deduction of A1 symmetry for the deep electronic states involved results from the observation of anticrossing effects. Large 'chemical shifts' between deep states of different impurities provide evidence for their strong localization. Fast electron capture onto these deep states at low temperature demonstrates their non-DX-like character. Present results and similar experiments with InSb show that three kinds of donor states, shallow, deep A1 and DX-like, are generally expected to exist in III-V compounds and alloys.