Multi-Channel Schottky-Gate BRIDGE HEMT Technology for Millimeter-Wave Power Amplifier Applications

We report on GaN-based field effect transistors with laterally-gated multiple 2DEG channels, called BRIDGE (buried dual gate) HEMT. A unique epi/device structure and operation of the BRIDGE HEMT demonstrate device characteristics suitable for efficient and linear millimeter-wave power amplifier MMIC applications. The BRIDGE HEMT reported in this work consists of 6 Si-modulation-doped AlGaN/AlN/GaN/AlGaN quantum well channels with a net 2DEG density of 4.8 × 1013 cm-2 and electron mobility of 1800 cm²/V·s. Co-optimization of the multi-channel epitaxial design and device process enabled to use Schottky-gates with lateral field plates in the BRIDGE HEMTs. The transistor exhibited good channel pinch-off at a threshold voltage of -5 V, flat Id-Vds curves, an off-state breakdown voltage of >30V, a knee current density of 1.6 A/mm and a transconductance of 0.5 S/mm at a gate voltage of 1.0 V. Load-pull measurement performed at 30 GHz exhibited a maximum output power density (Pout) of 7.1 W/mm at a quiescent drain voltage of 14 V, corresponding to a dynamic knee current density of 2 A/mm, with a power-added efficiency (PAE) of 39% under class-AB operation.