Physica Scripta

Pressure-dependent measurements on n+ GaAs (Si, Sn): The effect of deep donor (DX) states on the electrical properties and persistent photoconductivity

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Shubnikov-de Haas and persistent photoconductivity measurements are used to study the mobility, free electron density (n) and the occupancy of the DX centre in heavily doped n-GaAs as a function of doping level and hydrostatic pressure. The results show that the DX centre produces a resonant donor level between the γ - and L-conduction band minima at a concentration comparable with the doping level. For the Si-doped samples, comparison with local vibration mode measurements indicates that the DX level can be identified with SiGaThe level acts to pin the Fermi energy at electron concentrations around 1.8 ȕ 1019 cm‒3Analysis of the results indicates that macroscopic charge separation is not responsible for persistent photoconductivity in these samples. © 1988 IOP Publishing Ltd.