Geometrical magnetoresistance and hall mobility in gunn effect devices

Abstract

AbstractGeometrical magnetoresistance is developed as a technique for the determination of the Hall mobility of carriers in bulk effect GaAs microwave diodes at low electric fields. Spurious magnetoresistance effects due to inhomogeneities are analyzed and are shown to be negligible to first order for conductivity gradients oriented along the direction of the impressed electric field. For epitaxially grown GaAs, this is the predominant type of inhomogeneity and is due to diffusion of impurities out of the substrate or to a change in the doping during the growing process. The effect of contact resistance on the measurements of mobility is discussed as are a number of other practical aspects of the method, including the effect of misorientation of the magnetic field, the errors caused by finite aspect ratios of the diodes, heating by the measuring current, and the effect of magnetic shielding by parts of some commonly used microwave packages.The relationship between the Hall mobility and the magnetoresistance mobility is determined experimentally for GaAs at room temperature. The ratio is found to beμm/μH = 1.03±0.07.