InAlN Barrier Scaled Devices for Very High $f_{T}$ and for Low-Voltage RF Applications

We report excellent low-voltage (5 to ~ 10 V drain bias) microwave and millimeter-wave performance of deeply scaled InAn/AlN/GaN devices with field-plate gate of ~ 50-nm length, MBE regrown ohmic contacts, and sub-500-nm S-D spacing on four different wafers. These four wafers include also T-gate (no field-plate) devices with very thin passivation and smaller gate (~ 30 nm), which had (for reference) high fT/fmax of ~270/230 GHz, respectively, both for D- and E-mode devices. Their counterparts with field-plate gates (same gate geometry but with underlying dielectric) and 50-nm gates had lower fT/fmax but excellent performances at 10 GHz with up to 67%-69% power-added efficiency (PAE) at 6 V bias and 30 GHz with up to 14.4 dB associated gain and 2.6 W/mm and 39.6% PAE at 8 V bias. The noise figure of these devices at 10 GHz was ~ 0.25 dB with 3 V drain bias. We have measured the linearity [third-order intercept (TOI)] of 300- μm devices on another wafer with 90-nm field-plate gates: at 5 GHz and 5 V bias the devices had 31-dBm TOI with 0.31 W/mm, 18.5-dB gain, and 27.1% PAE.