Research on the Dependences of the Normally-Off GaN HEMT Input Parameters on the Operating Conditions in the GHz Band

In power electronics, the normally-off operating mode of a GaN HEMT (high electron mobility transistor) is often used when there is no current flow at the zero gate-source voltage and the channel current is modulated by applying positive bias to the gate terminal. Measurement of the GaN HEMT parameters in the GHz band is important for getting a physical interpretation of its functioning, as well as for developing large-signal and small-signal models. In this study, experimental research on the dependences of the normally-off GaN HEMT input parameters in different operating conditions in the GHz range is conducted. A procedure for measuring line inductance is proposed. The dependences of the input capacitance and input resistance on the gate voltage and drain voltage in the 5–20 GHz band are given. The obtained dependences can be applied for designing a small-signal model for a normally-off GaN HEMT.