High-Performance Microwave Gate-Recessed AlGaN/AlN/GaN MOS-HEMT With 73% Power-Added Efficiency

Gate-recessed AlGaN/AlN/GaN metal–oxide–semiconductor heterostructure high-mobility transistors (MOS-HEMTs) on SiC substrate are fabricated. The device with a gate length of 0.6
$\mu\hbox{m}$
and a gate periphery of 100
$\mu\hbox{m}$
exhibits a maximum dc drain current density of 1.59 A/mm at
$V_{\rm GS} = \hbox{3}\ \hbox{V}$
with an extrinsic transconductance
$(g_{m})$
of 374 mS/mm. An extrinsic current gain cutoff frequency
$(f_{T})$
of 19 GHz and a maximum oscillation frequency
$(f_{\max})$
of 50 GHz are deduced from S-parameter measurements. The output power density is 13 W/mm, and the associated power-added efficiency is 73% at 4-GHz frequency and 45-V drain bias. The power performance is comparable to state-of-the art AlGaN/GaN HEMTs, which demonstrates the great potential of gate-recessed MOS-HEMTs as a very promising alternative to GaN HEMTs.