Anisotropic negative magnetoresistance in a variable-thickness electron gas

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Abstract
The authors present further measurements of magnetoresistance in a parallel field of GaAs MESFETS. They find good agreement between these results and their previously proposed model for suppression of quantum interference when in the intermediate 3D to 2D regime. In particular, at high fields they have observed a temperature-independent magnetoresistance behaving as ln B in perpendicular orientation, implying 2D behaviour, but as B1/2 in a parallel orientation, implying 3D behaviour. The gradient of the high-field B1/2 correction was found to be within 5% of the theoretical value for a conductivity correction due to 3D quantum interference. At lower fields the new regime of temperature-dependent B1/2 behaviour is found in a parallel field. The transition between this regime and the pseudo-3D behaviour was found to occur when Lx equals approximately=0.4 of the channel thickness. At finite thicknesses, this effective length is altered by inelastic scattering, as would be expected from the effective-length-scale hypothesis.