We report 30-nm-gate-length InAlN/AlN/GaN/SiC high-electron-mobility transistors (HEMTs) with a record current gain cutoff frequency (f T ) of 370 GHz. The HEMT without back barrier exhibits an extrinsic transconductance (g m.ext ) of 650 mS/mm and an on/off current ratio of 10 6 owing to the incorporation of dielectric-free passivation and regrown ohmic contacts with a contact resistance of 0.16 Ω · mm. Delay analysis suggests that the high f T is a result of low gate-drain parasitics associated with the rectangular gate. Although it appears possible to reach 500-GHz f T by further reducing the gate length, it is imperative to investigate alternative structures that offer higher mobility/velocity while keeping the best possible electrostatic control in ultrascaled geometry.

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Textbook-like device characteristics are demonstrated in vertical GaN p-n diodes grown on bulk GaN substrates. These devices show simultaneously an avalanche breakdown voltage (BV) of >1.4 kV under reverse bias, an ideality factor plateau of $2.0 in a forward bias window followed by a near unity ideality factor of 1.1, which are consistently achieved over a temperature range of 300-400 K. At room temperature (RT), the diode with a mesa diameter of 107 lm showed a differential on-resistance R on of 0.12 mXcm 2 , thus resulting in a record figure-of-merit BV 2 /R on of $16.5 GW/cm 2 , which is the highest ever demonstrated in any semiconductors. Analytical models are used to fit experimental I-Vs; based on the recombination current with an ideality factor of $2.0, a Shockley-Read-Hall lifetime of 12 ns is extracted at RT with an estimated recombination center concentration of 3 Â 10 15 cm À3. V