First Demonstration of AlSiO as Gate Dielectric in GaN FETs; Applied to a High Performance OG-FET

Gate dielectricplays an integral role in advancing the performance and reliability of GaN-based transistors. Si-alloying of aluminum oxide (Al
₂
O
₃
) dielectrics have been shown to provide a promising route to improve gate dielectric properties in GaN. In this letter, we report on the first demonstration of a GaN FET with aluminum silicon oxide (AlSiO) as the gate dielectric. Vertical normally-off GaN MOSFETs were fabricated on bulk GaN substrate. Excellent dc performance was achieved with a breakdown voltage of 1.2 kV, an on-resistance of 2 mΩ.cm
²
, and a threshold voltage of 1.5 V (defined at I
_DS
= 1 μA/mm). A high breakdown electric-field of 2.3 MV/cm was calculated in these devices. In addition to vertical GaN MOSFET results, a comparative study of Al
₂
O
₃
and AlSiO-based in situ GaN MOS capacitors, including time-dependent dielectric breakdown characteristics is also presented.