Responsivity Measurements up to 110 GHz Using AlGaN/GaN HEMTs with Different Gate Size

The responsivity of microwave zero-bias detectors based on GaN high electron mobility transistors (HEMTs) is measured up to 110 GHz. A compact model based on static coefficients extracted from the DC output curves together with S-parameter measurements is able to replicate the detection results both when the radio-frequency power is fed into the drain or the gate terminals. A detailed analysis of the contribution of the gate-drain coupling to the RF responsivity allows to identify the origin of the frequency roll-off when shrinking the gate-size of the transistors.