Rectification in mesoscopic alternating current-gated semiconductor devices

We analyse the rectified dc currents resulting when a three-terminal semiconductor device with gate-dependent conductance is driven with an ac gate voltage. The rectified currents exhibit surprisingly complex behaviour as the dc source-drain bias voltage, the dc gate voltage, and the amplitude of the ac gate voltage are varied. We obtain good agreement between our data and a model based on simple assumptions about the stray impedances on the sample chip, over a wide frequency range. Secondly, we evaluate the small rectified currents flowing in tunable-barrier electron pumps operated in the pinched-off regime. These currents are at most 10−12 of the pumped current for a pump current of 100 pA. This result is encouraging for the development of tunable-barrier pumps as metrological current standards. Our method is applicable to many types of experiment which involve ac gating of a non-linear device, and where an undesirable rectified contribution to the measured signal is present.