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We report the first demonstration of self-aligned gate (SAG) β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) as a path toward eliminating source access resistance for low-loss power applications. The SAG process is implemented with a subtractively defined and etched refractory metal, such as Tungsten, combined with ion-implantation. We report experimental and modeled DC performance of a representative SAG device that achieved a maximum transconductance of 35 mS mm−1 and an on-resistance of ∼30 Ω mm with a 2.5 μm gate length. These results highlight the advantage of implant technology for SAG β-Ga2O3 MOSFETs enabling future power switching and RF devices with low parasitic resistance. [ABSTRACT FROM AUTHOR]

Heteroepitaxial Ga2O3 was grown on c-plane sapphire by molecular beam epitaxy, pulsed-laser deposition, and metalorganic chemical vapor deposition. Investigation by scanning transmission electron microscopy (STEM) revealed the presence of a three-monolayer-thick pseudomorphically grown layer of trigonal α-Ga2O3 at the interface between the c-plane sapphire substrate and the β-Ga2O3 independent of the growth method. On top of this pseudomorphically grown layer, plastically relaxed monoclinic β-Ga2O3 grew in the form of rotational domains. We rationalize the stable growth of the high-pressure trigonal α-phase of Ga2O3 in terms of the stabilization of the α-Ga2O3 phase by the lattice-mismatch-induced strain. [ABSTRACT FROM AUTHOR]