Fabrication and Performance of Au-Free AlGaN/GaN-on-Silicon Power Devices With ${\rm Al}_{2}{\rm O}_{3}$ and ${\rm Si}_{3}{\rm N}_{4}/{\rm Al}_{2}{\rm O}_{3}$ Gate Dielectrics

Au-free GaN-based metal-insulator-semiconductor high electron-mobility transistors grown on 150-mm Si substrates are reported. The device characteristics for three different processes are compared: an ohmic-first and a gate-first process with Al
₂
O
₃
-only as gate dielectric and a novel approach with a bilayer gate dielectric stack consisting of Si
₃
N
₄
and Al
₂
O
₃
. The Si
₃
N
₄
layer was deposited in situ in the metal-organic chemical vapor deposition reactor in the same growth sequence as the rest of the epilayer stack and the Al
₂
O
₃
layer was deposited ex situ by atomic layer deposition. Only the process with the bilayer gate dielectric results in robust devices with a breakdown voltage >600 V. The ohmic contact resistance for Au-free Ti/Al/W metallization scheme is <;1 Ω·mm. The devices show high maximum output current density (>0.4 A/mm); and low gate and drain leakage (<;10
^-10
A/mm). The maximum pulsed mode drain-source current of power bars with 20 mm gate width is 8 A. The specific on-state resistance is 2.9 m Ω·cm
²
.