Wide-bandwidth charge sensitivity with a radio-frequency field-effect transistor

We demonstrate high-speed charge detection at room temperature with single-electron resolution by using a radio-frequency field-effect transistor (RF-FET). The RF-FET combines a nanometer-scale silicon FET with an impedance-matching circuit composed of an inductor and capacitor. Driving the RF-FET with a carrier signal at its resonance frequency, small signals at the transistor's gate modulate the impedance of the resonant circuit, which is monitored at high speed using the reflected signal. The RF-FET driven by high-power carrier signals enables a charge sensitivity of 2 × 10⁻⁴ e/Hz^0.5 at a readout bandwidth of 20 MHz.