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

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 Al₂O₃-only as gate dielectric and a novel approach with a bilayer gate dielectric stack consisting of Si₃N₄ and Al₂O₃. The Si₃N₄ 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 Al₂O₃ 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·cm².