High-Performance AlGaN/GaN HEMTs With Hybrid Schottky-Ohmic Drain for Ka-Band Applications

A hybrid Schottky-ohmic drain technology for millimeter-wave (mmW) AlGaN/GaN high-electron-mobility transistors (HEMTs) is proposed. The Schottky metal extension in the ohmic region of drain reduces the actual source-drain spacing, resulting in a smaller ON-resistance and a higher maximum current. Extended Schottky metal in the drain region modulates the electric-field distribution, thereby leading to an improved breakdown voltage, suppressed current collapse, and high reliability. Compared with the ohmic drain, the current gain cutoff frequency (f(T)) was improved from 64 to 76 GHz, and the maximum oscillation frequency (f(max)) was improved from 125 to 157 GHz, resulting from the decreased parasitic drain resistance (R-d). Moreover, large-signal measurements in continuous wave (CW) at 30 GHz demonstrated a peak power-added efficiency (PAE) of 45.5% and a saturated output power density (P-sat) of 8.5 W/mm at V-ds = 30 V. In addition, the direct current (DC) and radio frequency (RF) characteristics showed a negligible degradation after large-signal measurements at 30 GHz.

Automated summary

A hybrid Schottky-ohmic drain technology is proposed for high-frequency transistors, which can significantly improve the performance of the devices, including reducing resistance, increasing breakdown voltage, suppressing current collapse, and maintaining good DC and RF characteristics after large-signal measurements.