Two-level model and magnetic field effects on the hysteresis inn−GaAs

Abstract

Efforts are made in this work to interpret the experimentally observed magnetic effects on the hysteretic $I\text{\ensuremath{-}}V$ curve for an $n\text{\ensuremath{-}}\mathrm{GaAs}$ semiconductor through a two-impurity-level model with the assumptions of spatial homogeneity in current flow direction and instantaneous energy balance. We construct the model by considering carefully the Landau level shifts for the electrons in the conduction band, the magnetoresistance property, and the modification on the cross sections of the impact ionization. With the inclusions of the effects from the carrier electron temperature variation and the field-dependent electron mobility, we are able to describe the hysteretic $I\text{\ensuremath{-}}V$ characteristics satisfactorily for the case of applying either a longitudinal or a transverse magnetic field simultaneously within a single model. Our numerical results show that when the applied longitudinal magnetic field $B$ increases, the holding voltage of the hysteresis shifts towards a higher value, while the breakdown voltage remains almost fixed and thus the width of the hysteresis decreases. Above a critical magnetic field intensity $86\phantom{\rule{0.3em}{0ex}}\mathrm{mT}$, the hysteresis vanishes. Under the transverse magnetic field, the breakdown voltage of the hysteresis shifts significantly towards the higher direction with a stronger magnetic field $B$, and therefore a considerably wider hysteresis width. The dynamic behavior of our model has displayed the same features of the experimental observations described by Aoki, Kondo, and Watanabe in Solid State Commun. 77, 91 (1991).