900 V/1.6 ${\rm m}\Omega\cdot{\rm cm}^{2}$ Normally Off ${\rm Al}_{2}{\rm O}_{3}/{\rm GaN}$ MOSFET on Silicon Substrate

In this paper, we report the device performance of a high-voltage normally off
${\rm Al}_{2}{\rm O}_{3}/{\rm GaN}$
MOSFET on the Si substrate. Normally off operation is obtained by multiple cycles of
${\rm O}_{2}$
plasma oxidation and wet oxide-removal gate recess process. The recessed normally off GaN MOSFET with 3
$\mu{\rm m}$
gate-drain distance exhibits a maximum drain current of 585 mA/mm at 9 V gate bias. The threshold voltage of the MOSFET is 2.8 V with a standard derivation of 0.2 V on the sample with an area of 2
$\,\times\,$
2
${\rm cm}^{2}$
. The gate leakage current is below
$10^{-6}~{\rm mA}/{\rm mm}$
during the whole gate swing up to 9 V and the
${\rm I}_{{\scriptstyle{\rm ON}}}/{\rm I}_{{\scriptstyle {\rm OFF}}}$
ratio is larger than
$10^{9}$
, indicating the good quality of
${\rm Al}_{2}{\rm O}_{3}$
gate insulator. The MOSFET with 10
$\mu{\rm m}$
gate-drain distance shows a three terminal OFF-state breakdown voltage (BV) of 967 V at zero gate-source bias with a drain leakage current criterion of 1
$\mu{\rm A}/{\rm mm}$
. The specific ON-resistance
$(R_{{{\scriptstyle {\rm ON}}},{\rm SP}})$
of the device is 1.6
${\rm m}\Omega\,{\cdot}\,{\rm cm}^{2}$
and the power figure of merit
$({\rm BV}^{2}/R_{{{\scriptstyle {\rm ON}}},{\rm SP}})$
is 584
${\rm MW}/{\rm cm}^{2}$
.