Quantum point contact transistor with high gain and charge sensitivity

Abstract

We analyze the potential performance of quantum point contact (QPC) devices in charge detection applications. For the standard QPC structure we show that the charge sensitivity is strongly dependent on gate geometry and can be close to the quantum limit, and that the gain parameter is less than one under bias conditions where the charge sensitivity is optimized. We propose a novel QPC device consisting of two split gates for defining the QPC and a third gate which can be used to filter out hot electrons that are emitted from the QPC. We show that this proposed device can have a high gain and a charge sensitivity close to that of single electron transistors. The device can be realized using high quality GaAs/AlGaAs with a two-dimensional electron gas and standard nanofabrication techniques. Unlike single electron transistors, the gain of the proposed device does not depend on the charge configuration near the active region of the device. Therefore the device can be used as an electrometer without a feedback charged locked loop and multiple devices can easily be integrated.