First demonstration of RF N-polar GaN MIS-HEMTs grown on bulk GaN using PAMBE

Abstract

Nitrogen polar (N-Polar) GaN high-electron mobility transistors (HEMT) targeting high efficiency in millimeter wave power amplification applications were fabricated on epitaxial layers grown by plasma assisted molecular beam epitaxy (PAMBE) on on-axis semi-insulating bulk GaN substrates. On-state current density of ∼1 A mm−1 was observed on transistors with LG = 0.75 μm, LGS = 0.5 μm and LGD = 3.75 μm. In a deep class AB mode of operation, devices fabricated on epitaxial structures with these substrates demonstrated 60% higher electron channel mobility compared to devices fabricated with a similar epitaxial structure grown on sapphire substrates using metal-organic chemical vapor deposition. As the first demonstration of N-polar GaN-on-GaN MISHEMT for power amplifier applications, the devices discussed in this letter bridge a path towards achieving higher power gain and efficiency for millimeter-wave N-polar GaN HEMTs.