0.1- $\mu \text{m}$ Atomic Layer Deposition Al 2 O 3 Passivated InAlN/GaN High Electron-Mobility Transistors for E-Band Power Amplifiers

High-performance 0.1- $\mu \text{m}$ InAlN/GaN high electron-mobility transistors (HEMTs) have been successfully developed for power amplifiers operating at E-band (targeting 71–76 and 81–86-GHz bands). High maximum drain current of 1.75 A/mm and maximum extrinsic transconductance of 0.8 S/mm have been achieved for depletion-mode devices. Enhancement-mode HEMTs have also shown maximum drain current of 1.5 A/mm and maximum extrinsic transconductance of 1 S/mm. The selection of atomic layer deposition aluminum oxide (Al 2 O 3 ) for device passivation enables a two-terminal breakdown voltage of $\sim 25$ V, excellent subthreshold characteristics as well as the pulsed- IV featuring little current collapse for both types of HEMTs. When biased at a drain voltage of 10 V, a first-pass two-stage power amplifier design based on 0.1- $\mu \text{m}$ depletion-mode devices has demonstrated an output power of 1.43 W with 12.7% power-added efficiency at 86 GHz, a level of performance that has been attained previously only by state-of-the-art counterparts based on AlGaN/GaN HEMTs at a much higher drain bias and compression level.