Electrical properties of molecular beam epitaxial GaAs grown at 300–450°C

We use the Hall effect and a new charge-transfer technique to study molecular beam epitaxial GaAs grown at the low substrate temperatures of 300–450°C. Layers grown from 350–450°C are semi-insulating (resistivity greater than 107 Ω-cm), as grown, because of an AsGa-related donor (not EL2) at EC-0.65 eV. The donor concentrations are about 2×1018 cm−3 and 2×1017 cm−3 at growth temperatures of 300 and 400°C, respectively, and acceptor concentrations are about an order of magnitude lower. Relatively high mobilities (∼5000 cm2/V s) along with the high resistivities make this material potentially useful for certain device applications.