ANOMALOUS HALL-EFFECT RESULTS IN LOW-TEMPERATURE MOLECULAR-BEAM-EPITAXIAL GAAS - HOPPING IN A DENSE EL2-LIKE BAND

Molecular-beam-epitaxial GaAs grown at very low temperatures (200°C) exhibits anomalous Hall-effect properties. Here we show conclusively that the room-temperature conduction is due to activated (nearest-neighbor) hopping in a deep defect band of concentration 3×1019 cm-3, and energy Ec-0.75 eV, along with conduction due to free carriers thermally excited from this band. At low measurement temperatures, variable-range hopping [exp(-T0/T)1/4] prevails. The conduction-band mobility can be well explained by neutral-deep-donor scattering in parallel with lattice scattering. © 1990 The American Physical Society.