Effects of TMAH Treatment on Device Performance of Normally Off $\hbox{Al}_{2}\hbox{O}_{3}/\hbox{GaN}$ MOSFET

Normally off Al
₂
O
₃
/GaN MOSFETs are fabricated by utilizing a simple tetramethylammonium hydroxide (TMAH) treatment as a postgate-recess process. The TMAH-treated device with a gate length of 2.5 μm exhibited excellent device performances, such as a threshold voltage of 3.5 V, a maximum drain current of 336 mA/mm, and a breakdown voltage of 725 V, along with extremely small gate leakage current of about 10
^-9
A/mm at
V
_gs
= 15 V, which is approximately six orders lower in magnitude compared to that of the device without TMAH treatment.