Semiconducting/semi-insulating reversibility in bulk GaAs.

Bulk, liquid-encapsulated Czochralski GaAs may be reversibly changed from semiconducting (ρ∼1 Ω cm) to semi-insulating (ρ∼107 Ω cm) by slow or fast cooling, respectively, following a 5 h, 950 °C soak in an evacuated quartz ampoule. This effect has been studied by temperature-dependent Hall-effect, photoluminescence, infrared absorption, mass spectroscopy, and deep level transient spectroscopy measurements. Except for boron, the samples are very pure, with carbon and silicon concentrations less than 3×1014 cm-3. Donor and acceptor concentrations, on the other hand, are in the mid 1015 cm-3 range, which means that the compensation is primarily determined by native defects, not impurities. A tentative model includes a donor at EC-0.13 eV, attributed to VAs-AsGa, and an acceptor at EV+0.07 eV, attributed to VGa-GaAs. [ABSTRACT FROM AUTHOR]