Tu4E-4 Multi-channel Schottky-gate BRIDGE HEMT Technology for Millimeter-Wave Power Amplifier Applications

Abstract

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/AIN/GaN/AlGaN quantum well channels with a net 2DEG density of 4.8 &#x00D7; 10¹³ cm^-2and electron mobility of 1800 cm²/V&#x00B7;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 &#x2212;5 V, flat <tex>$\boldsymbol{I}_{\mathbf{d}}-\boldsymbol{V}_{\mathbf{d}\mathbf{s}}$</tex> curves, an off-state breakdown voltage of <tex>$&#x003E; 30\mathbf{V}$</tex>) 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 <tex>$(\boldsymbol{p}_{\mathbf{o}\mathbf{u}\mathbf{t}})$</tex> 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&#x0025; under class-AB operation.