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Silicon substrates offer an attractive substrate platform for GaN RF and power electronics. In this work, we address the key challenges and provide solutions for the RF-MBE growth of GaN high-electron-mobility transistors (HEMTs) on Si(111). Moreover, by developing low-leakage buffer layers and employing raised source/drain regrown ohmic contacts, high-performance HEMTs are realized at a significantly lower process temperature by plasma MBE than by MOCVD. This is expected to motivate further ideas for the integration of GaN with silicon that go beyond RF and power electronics into the regime of low-power digital logic by exploiting the unique polarization properties of GaN.

Superior electronic and thermal properties have made InAlN/GaN high-electron-mobility transistors (HEMTs) an attractive candidate for power electronics applications. However, their high gate leakage current remains a serious challenge affecting the reliability and performance of these heterostructures. Leakage paths through dislocations or by percolation through inhomogeneities in the InAlN alloy barrier restrict the voltage handling capability of these HEMTs. In this work, we show that surface treatment with KOH greatly reduces the gate leakage current. Consequently, the switching characteristics of the HEMTs improve, and they exhibit lower subthreshold slopes and improved breakdown characteristics. The finding should be of interest for both microwave and power electronics applications of nitride HEMTs.