A 177–183 GHz High-Power GaN-Based Frequency Doubler With Over 200 mW Output Power

A GaN Schottky barrier diode (SBD) on SiC for frequency doubler applications was fabricated with a N-/N+ GaN stack of 200 nm/1500 nm in thickness and 5 × 10
¹⁷
cm
^-3
/8 × 10
¹⁸
cm
^-3
in doping densities, respectively. A cut-off frequency of 459 GHz at zero bias and reverse breakdown voltage of 15.4 V were obtained. A quartz glass circuit with flip-chip-mounted GaN SBDs was inserted between split-waveguide blocks to form a balanced frequency doubler. When driven with 2 W input power in pulsed mode, measured output power was 200-244 mW from 177-183 GHz with efficiency 9.5-11.8%.