Gallium Oxide has undergone rapid technological maturation over the last decade, pushing it to the forefront of ultra-wide band gap semiconductor technologies. Maximizing the potential for a new semiconductor system requires a concerted effort by the community to address technical barriers which limit performance. Due to the favorable intrinsic material properties of gallium oxide, namely, critical field strength, widely tunable conductivity, mobility, and melt-based bulk growth, the major targeted application space is power electronics where high performance is expected at low cost. This Roadmap presents the current state-of-the-art and future challenges in 15 different topics identified by a large number of people active within the gallium oxide research community. Addressing these challenges will enhance the state-of-the-art device performance and allow us to design efficient, high-power, commercially scalable microelectronic systems using the newest semiconductor platform.

Beta phase Gallium Oxide (BGO) is an emerging ultra-wide bandgap semiconductor with disruptive potential for ultra-low power loss, high-efficiency power applications. The critical field strength is the key enabling material parameter of BGO which allows sub-micrometer lateral transistor geometry. This property combined with ion-implantation technology and large area native substrates result in exceptionally low conduction power losses, faster power switching frequency and even radio frequency power. We present a review of BGO epitaxial materials and lateral field-effect transistors developments, highlight early achievements and discuss engineering solutions with power switching and radio frequency applications in mind.

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.

DC, small, and large signal results are shown under continuous wave and pulsed conditions for a β-Ga 2 O 3 metal-oxide-semiconductor field-effect transistor operating at 1 and 2 GHz. The device has a maximum transducer gain, maximum output power, and peak power added efficiency of 13 dB (15 dB), 715 mW/mm (487 mW/mm), and 23.4% (21.2%), respectively at 1 GHz (2 GHz). We observe the continuous wave output power is limited to 213 mW/mm by drain dispersion likely from surface or interface traps in the gatedrain region as indicated by pulsed IV measurements. High parasitic resistances, as indicated by high knee voltages, also limit the power performance under continuous and pulsed large signal conditions.