RF High-Power Operation of AlGaN/GaN HEMTs Epitaxially Grown on Diamond

We epitaxially grow AlGaN/GaN high-electron-mobility transistors (HEMTs) on IIa-type single-crystal diamond (111) substrates. A 0.4-μm gate-length HEMT showed a dc drain-current density I_DS of 770 mA/mm and a breakdown voltage of 165 V. In the RF large-signal measurements at 1 GHz, an RF output-power density P_OUT of 2.13 W/mm was obtained. This is the first report of RF power operation of AlGaN/GaN HEMTs epitaxially grown on diamond. The AlGaN/GaN HEMTs epitaxially grown on diamond showed a low thermal resistance of 1.5 K·mm/W.