Current-voltage characteristics of quantum point contacts in the high-bias regime

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Abstract
The current flowing through a quantum point contact defined in the plane of a two-dimensional electron gas does not saturate under high source-drain bias voltages as expected from simple theoretical considerations. We propose an analytical model which explains this observation in terms of the increased current contribution from normally non-conducting subbands under high source-drain bias. Furthermore, the observed current-voltage characteristics are asymmetric with respect to changing the polarity of the bias voltage. We explain this effect by considering the influence of the bias voltage on the effective point contact geometry. A further consequence of this model is the prediction of negative differential resistance under conditions of high positive forward bias in very narrow channels.