The role of deep-level centers and compensation in producing semi-insulating GaAs

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Abstract
A mathematical model, involving a set of gap states, is considered for interpreting the unusual properties of semi-insulating GaAs. Although GaAs should be an extrinsic semiconductor at room temperature, often it has carrier concentrations and resistivities which are characteristic of pure intrinsic material, and the electrical properties can be surprisingly uniform. Such behavior is shown to arise if a deep donor level is located close to the center of the gap and if the deep donor concentration is comparable to a net shallow-level concentration (NA−ND) so that compensation exists. It is demonstrated that the present model yields good agreement with presently available experimental data.