Anomalous Hall-effect results in low-temperature molecular-beam-epitaxial GaAs: Hopping in a denseEL2-like band

Abstract

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×${10}^{19}$ ${\mathrm{cm}}^{\mathrm{-}3}$, and energy ${\mathit{E}}_{\mathit{c}}$-0.75 eV, along with conduction due to free carriers thermally excited from this band. At low measurement temperatures, variable-range hopping [σ∝exp(-${\mathit{T}}_0$/T${)}^{1/4}$] prevails. The conduction-band mobility can be well explained by neutral-deep-donor scattering in parallel with lattice scattering.