Pressure assisted studies of thermal emission from resonant DX centres: new evidence for multi-level structure of Si-DX centre in GaAlAs

Thermal emission from resonant DX levels of the Si centre in GaAlAs with low Al content, filled with electrons at high pressure, is studied at ambient pressure. The results yield evidence of the multi-level character of the centre. Well separated contributions of three DX levels, related to different local environments of the relaxed Si atom, are observed in GaAlAs samples with Al content of x=0.15 and x=0.2. The relative positions of the levels are found. A new argument supporting the negative U(D - ) character of the centre is provided. The method used allowed a GaAs-like configuration of Si in GaAlAs with up to 28% Al to be obtained.