Abstract
Identification of the deep levels responsible for the electrical compensation of Cr-doped semi-insulating GaAs has been lacking in spite of the increasing importance of this material. Transport measurements on bulk-grown semi-insulating GaAs single crystals with three different Cr concentrations are presented to shed light on this problem. Alternative models for the electrical compensation are discussed. A detailed analysis of the temperature dependence of the resistivity shows that the ’’conventional’’ model in which deep Cr acceptors compensate residual shallow donors is incorrect. A more elaborate model which includes both a deep acceptor and a deep donor is proposed to properly interpret the experimental data. The deep donor level, located between 0.64 and 0.72 eV from the conduction band, is assigned to oxygen.
Published Version
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