ScAlN-GaN Transistor Technology for Millimeter-wave Ultra-high Power and Efficient MMICs

Development of MBE-grown ScAlN-based heterostructure field effect transistors (HFETs) for millimeter-wave operation at Ka- and W-band frequencies are reported. Fabricated 2-finger transistors with non-alloyed, ohmic regrowth contacts achieved excellent DC performance with maximum current density (
$(\mathrm{I}_{\text{MAX}}$
) and peak transconductance
$(\mathrm{g}_{\mathrm{M}})$
of up to 2.5 A/mm and >0.7 S/mm, respectively. Continuous-wave (cw), large-signal RF (LS-RF) output power density (POUT) and power added efficiency (PAE) of >9 W/mm and >25% were respectively achieved from load pull characterization at 30 GHz when operated up to 40 V. At 94 GHz, POUT and PAE of >3.6 W/mm and 24% respectively were achieved at 10 V operation. This marks not only the best millimeter-wave RF power density performance of ScAlN/GaN transistors at 30 GHz to date but also the first demonstration of RF performance at W-band with
$> 2\mathrm{X}$
higher POUT than similar AlGaN-based transistors thereby paving the path for highly compact, millimeter-wave amplifiers (narrow and wideband) with considerably higher power and efficiency.