A nonlinear transport device with no intrinsic threshold

A ballistic rectifier, based on guidance of carriers by a triangular antido t, is shown to be both experimentally and theoretically capable of operatin g for weak signals. At T = 4.2 K, we find that the ballistic rectifier work s when the input voltage is as low as 0.5 mV, the same order of k(B)T. Base d on an extended Landauer-Buttiker formula for nonlinear transport, we show that even when the input signal is much smaller than k(B)T, temperature ha s no obvious influence on the rectification effect. (C) 1999 Academic Press .