Determination of transport coefficients in high mobility heterostructure systems in the presence of parallel conduction

The effect of a parasitic parallel conducting layer on the measurement of longitudinal and transverse magnetoresistances of a high mobility two-dimensional (2D) electron gas in modulation-doped heterostructures is considered. A circuital analysis which takes into account the effect of circulating currents at the Hall contacts is presented, and previous descriptions of this situation are shown to be inapplicable. The resultant equations correctly predict the behavior of the longitudinal and transverse magnetoresistances at both high and low magnetic fields, and correlate well with the measured values. They also allow one to accurately determine the 2D mobility and density as well as the parallel layer resistivity.