30-W/mm GaN HEMTs by field plate optimization

GaN high-electron-mobility-transistors (HEMTs) on SiC were fabricated with field plates of various dimensions for optimum performance. Great enhancement in radio frequency (RF) current-voltage swings was achieved with acceptable compromise in gain, through both reduction in the trapping effect and increase in breakdown voltages. When biased at 120 V, a continuous wave output power density of 32.2 W/mm and power-added efficiency (PAE) of 54.8% at 4 GHz were obtained using devices with dimensions of 0.55×246 μm² and a field-plate length of 1.1 μm. Devices with a shorter field plate of 0.9 μm also generated 30.6 W/mm with 49.6% PAE at 8 GHz. Such ultrahigh power densities are a dramatic improvement over the 10-12 W/mm values attained by conventional gate GaN-based HEMTs.