GaN-based pin diodes were fabricated and characterised for microwave switching IC applications. The fabricated GaN pin diode with a p-metal diameter of 50 mu m demonstrated a 3.8 V turn-on voltage, a 370 V breakdown voltage and a power figure of merit value of 178.5 MW/cm(2) with an on-state resistance of 29 Omega and an off-state capacitance of 47 fF. To the authors' best knowledge, this result is the first RF characterisation of the GaN pin diode for microwave IC applications.