GaN-based radio-frequency planar inter-digitated metal-insulator-semiconductor varactors

The first demonstration of radio-frequency planar inter-digitated metal-insulator-semiconductor (PIDMIS) varactors fabricated on AlGaN/GaN heterostructures is reported. The PIDMIS varactors achieved good quality factor (Q-factor) and tuning range. The Q-factor of PIDMIS varactors is discussed, based on a physical equivalent circuit which takes into account the capacitance of the active channel, fixed insulator capacitance, parasitic resistances and leakage current through the substrate. The experimental data shows that for identical substrate structures, the quality factor varies with different design parameters.