AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistors on SiC substrates

We report on AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistors (MOS-HFETs) grown over insulating 4H–SiC substrates. We demonstrate that the dc and microwave performance of the MOS-HFETs is superior to that of conventional AlGaN/GaN HFETs, which points to the high quality of ${\mathrm{SiO}}_2/\mathrm{AlGaN}$ heterointerface. The MOS-HFETs could operate at positive gate biases as high as +10 V that doubles the channel current as compared to conventional AlGaN/GaN HFETs of a similar design. The gate leakage current was more than six orders of magnitude smaller than that for the conventional AlGaN/GaN HFETs. The MOS-HFETs exhibited stable operation at elevated temperatures up to $\text{300\hspace{0.05em}°}\mathrm{C}$ with excellent pinch-off characteristics. These results clearly establish the potential of using AlGaN/GaN MOS-HFET approach for high power microwave and switching devices.