Low Leakage Current and High-Cutoff Frequency AlGaN/GaN MOSHEMT Using Submicrometer-Footprint Thermal Oxidized TiO2/NiO as Gate Dielectric

AlGaN/GaN metal oxide semiconductor high electron mobility transistors (MOSHEMTs) with thick
$({>}{\rm 35}~{\rm nm})$
, high-
$\kappa~({\rm TiO}_{{2}}/{\rm NiO})$
, submicrometer-footprint (0.4
$\mu{\rm m}$
) gate dielectric are found to exhibit two orders of magnitude in lower gate leakage current (
${\sim}{\rm 1}~{\rm nA}/{\rm mm}$
up to
${+}{\rm 3}\hbox{-}{\rm V}$
applied gate bias), higher
$I_{\rm{MAX}}$
(709 mA/mm), and higher drain breakdown voltage, compared to Schottky barrier (SB) HEMTs of the same geometry. The maximum extrinsic transconductance of both the MOSHEMTs and the SBHEMTs with
$2\times80\hbox{-}\mu{\rm m}$
gate fingers is measured to be 149 mS/mm. The addition of the submicrometer-footprint gate oxide layer only results in a small reduction of the current gain cutoff frequency (21 versus 25 GHz, derived from
$S$
-parameter test data) because of the high permittivity
$(\kappa\approx 100)$
of the gate dielectric. This high-performance submicrometer-footprint MOSHEMT is highly promising for microwave power amplifier applications in communication and radar systems.