Te-related DX centre of GaAs and AlGaAs

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Abstract
The pressure dependences of the electrical conductivity and Hall coefficient have been studied for GaAs and AlxGa1-xAs (x=0.20 and 0.25) heavily doped with Te. The results obtained show that for a GaAs crystal the resonant donor level related to Te is located approximately 0.45 eV above the conduction band minimum. The effect of persistent photoconductivity observed at high pressures proves the DX-like character of this donor state. Comparison of the data on the energetic position of the DX level illustrates its strong chemical energetic dependence (for Si, Sn and S dopants an EDX value of around 0.3 eV has been reported previously). It appears that Te represents an impurity which is very suitable for testing the microscopic models of the DX centre. Studies of processes of the thermal recovery after high pressure freeze-out of electrons on the metastable states of the DX centres clearly demonstrate the multicomponent structure of the DX state in AlGaAs samples.