Local Structure Around Te in Heavily Doped GaAs:Te using X-Ray Absorption Fine Structure

Abstract

The annealing of heavily doped GaAs:Te can signicantly change the free electron concentration in a reversible manner. These changes of electrical properties are accompanied by the structural changes of GaAs:Te solid solution. We used X-ray Absorption Fine Structure at K-edge of tellurium to determine local changes around Te atoms for dierent states of the GaAs:Te crystals caused by the annealing corresponding to dierent electron concentrations. The best EXAFS t for the samples with high electron concentration was obtained for the substitutional TeAs model with elongated TeGa bonds (as compared to the AsGa distance). For the samples in the low concentration state the best t was for the pairs of Te atoms forming a rhombohedral symmetry double-DX centre, with the proportional admixture of the substitutional tellurium PACS: 61.05.cj, 61.72.uj