Delta-doped AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors with high breakdown voltages

The fabrication and dc characteristics of AlGaN/GaN-based heterostructure field-effect transistors (HFETs) by employing the delta-doped barrier and the SiO2 insulated gate are reported. The device grown on sapphire substrate has a high drain-current-driving and gate-control capabilities as well as a very high gate-drain breakdown voltage of 200 V for a gate length of 1 mum and a source-drain distance of 3 mum. The incorporation of the SiO2 insulated gate and the delta-doped barrier into HFET structures reduces the gate leakage and improves the two-dimensional channel carrier mobility, and thereby allows one to take the inherent advantage of AlGaN/GaN HFETs with relatively high Al contents-the device structure is capable to deliver higher electron density (or drain current density) yet ensures an excellent pinch-off property as well as small gate leakage current. These characteristics indicate a great potential of this structure for high-power-microwave applications. (C) 2002 American Institute of Physics.