Increased Mobility in Enhancement Mode 4H-SiC MOSFET Using a Thin SiO2 / Al2O3 Gate Stack

A field effect mobility of 125 cm
$^{\textsf {2}}/\text{V}\cdot \text{s}$
and a subthreshold slope of 130 mV/dec were obtained in enhancement mode 4H-SiC MOSFETs with a channel length of
$2~\mu \text{m}$
. The fabricated devices utilized a gate stack comprising a 0.7 nm thin thermal SiO
₂
, thereby reducing defects following oxidation, and a 40 nm thick Al
₂
O
₃
formed by atomic layer deposition. A high mobility was maintained over a wide gate voltage range and resulted in increases of up to
$120\times $
in drain current for the same gate overdrive voltage compared to MOSFETs having a thicker thermal SiO
₂
gate stack with the same effective oxide thickness fabricated alongside. Nitridation is not included in either MOSFET process.