Photoexcited states of DX centers in Si doped AlxGa1−xAs

Abstract

Deep level transient spectroscopy (DLTS) and single shot capacitance techniques were used to investigate Si doped AlxGa1−xAs with Al compositions ranging from 0.30 to 0.59. Under illumination, an additional DLTS peak was observed in samples with Al compositions close to x=0.38. This peak has been shown to originate from a localized state with an energy level shallower than the DX ground state and energy barriers for both electron emission and capture processes. Persistent photoconductivity effects related to this state were observed below 50 K. Evidence is provided that this state is a metastable state of the Si donor. Its origin is discussed in terms of the intermediate state of a negative U DX center and a metastable negative U configuration of the Si donor. A further photoinduced DLTS peak was observed within a narrow Al composition range that has been identified as the shallowest DX level of the four distinct DX levels originating from different local environments of the donors.