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.

We have studied the properties of Si, Ge shallow donors and Fe, Mg deep acceptors in β-Ga2O3 through temperature dependent van der Pauw and Hall effect measurements of samples grown by a variety of methods, including edge-defined film-fed (EFG), Czochralski (CZ), molecular beam epitaxy (MBE), and low pressure chemical vapor deposition (LPCVD). Through simultaneous, self-consistent fitting of the temperature dependent carrier density and mobility, we are able to accurately estimate the donor energy of Si and Ge to be 30 meV in β-Ga2O3. Additionally, we show that our measured Hall effect data are consistent with Si and Ge acting as typical shallow donors, rather than shallow DX centers. High temperature Hall effect measurement of Fe doped β-Ga2O3 indicates that the material remains weakly n-type even with the Fe doping, with an acceptor energy of 860 meV relative to the conduction band for the Fe deep acceptor. Van der Pauw measurements of Mg doped Ga2O3 indicate an activation energy of 1.1 eV, as determined from the temperature dependent conductivity.

No abstract

No abstract

No abstract

No abstract

A new device-first low-temperature bonded gallium nitride (GaN)-on-diamond high-electronic mobility transistor (HEMT) technology with state-of-the-art, radio frequency (RF) power performance is described. In this process, the devices were first fabricated on a GaN-on-silicon carbide (SiC) epitaxial wafer and were subsequently separated from the SiC and bonded onto a high-thermal-conductivity diamond substrate. Thermal measurements showed that the GaN-on-diamond devices maintained equivalent or lower junction temperatures than their GaN-on-SiC counterparts while delivering more than three-times higher RF power within the same active area. Such results demonstrate that the GaN device transfer process is capable of preserving intrinsic transistor electrical performance while taking advantage of the excellent thermal properties of diamond substrates. Preliminary step-stress and room-temperature, steady-state life testing shows that the low-temperature bonded GaN-on-diamond device has no inherently reliability limiting factor. GaN-on-diamond is ideally suited to wideband electronic warfare (EW) power amplifiers as they are the most thermally challenging due to continuous wave (CW) operation and the reduced power-added efficiency obtained with ultra-wide bandwidth circuit implementations.

No abstract