Demonstration of high Johnson’s figure of merit (f t × VBR >20 THz·V) and f max × VBR (>42 THz·V) for Al0.66Ga0.34N channel MISHEMT on bulk AlN substrates

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In this paper, a metal-organic chemical vapor deposition (MOCVD) grown Al0.66Ga0.34N channel metal-insulator-semiconductor-high-electron-mobility-transistor (MISHEMT) with a scaled T-gate structure was fabricated on a single-crystal bulk AlN substrate. A device with 4 μm source-to-drain spacing achieved a record-high Johnson’s figure of merit (JFOM) of 20.92 THz·V, enabled by the high-Al channel, high-quality substrate, and gate field-plate. The corresponding cutoff and maximum oscillation frequencies are 22.5 GHz and 46 GHz, respectively, with a breakdown voltage of 930 V. A current collapse of 15% was observed under 30 V drain bias, indicating excellent radio-frequency (RF) performance and the potential of bulk-AlN-based AlGaN channel high-electron-mobility-transistors (HEMTs) for advanced RF applications.