Radio-frequency point-contact electrometer

We fabricate and characterize a radio-frequency semiconductor point-contact (rf-PC) electrometer analogous to radio-frequency single-electron transistors (rf-SETs) [see Schoelkopf , Science 280, 1238 (1998)]. The point contact is formed by surface Schottky gates in a two-dimensional electron gas in an AlGaAs/GaAs heterostructure. In the present setup, the PC is operating as a simple voltage-controlled resistor rather than a quantum point contact and demonstrates a charge sensitivity of about 2x10(-1)e/root Hz at a bandwidth of 30 kHz without the use of a cryogenic rf preamplifier. Since the impedance of a typical point-contact device is much lower than the impedance of the typical SET, a semiconductor-based rf-PC, equipped with practical cryogenic rf preamplifiers, could realize an ultrafast and ultrasensitive electrometer.