A high current density of 1 kA/cm2 is experimentally realized in enhancement-mode Ga2O3 vertical power metal-insulator field-effect transistors with fin-shaped channels. Comparative analysis shows that the more than doubled current density over the prior art arises from a larger transistor channel width; on the other hand, a wider channel also leads to a more severe drain-induced barrier lowering therefore premature transistor breakdown at zero gate-source bias. The observation of a higher current density in a wider channel confirms that charge trapping in the gate dielectric limits the effective field-effect mobility in these transistor channels, which is about 2× smaller than the electron mobility in the Ga2O3 drift layer. The tradeoff between output-current density and breakdown voltage also depends on the trap density. With minimal trap states, the output current density should remain high while breakdown voltage increases with decreasing fin-channel width.

β-Ga2O3 vertical trench Schottky barrier diodes (SBDs) are realized, demonstrating superior reverse blocking characteristics than the co-fabricated regular SBDs. Taking advantage of the reduced surface field effect offered by the trench metal-insulator-semiconductor structure, the reverse leakage current in the trench SBDs is significantly suppressed. The devices have a higher breakdown voltage of 1232 V without optimized field management techniques, while having a specific on-resistance (Ron,sp) of 15 mΩ cm2. An ultra-low leakage current density of <1 μA/cm2 is achieved before breakdown, the lowest among all reported Ga2O3 Schottky barrier diodes. Fast electron trapping and slow de-trapping near the Al2O3/Ga2O3 interface are observed by repeated C-V measurements, which show an interface state ledge and positive shifts of flat-band voltages with increasing voltage stress. By comparison between pulsed and DC measurements, the device self-heating effect and the trapping effect are uncoupled. It is found that the trapping effect at the trench sidewall affects the on-resistance of the trench SBDs, even under pulsed conditions. With reduced trapping effect and better field management technique, the trench SBDs could further harvest the promising material properties of β-Ga2O3.

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The nitride semiconductor materials GaN, AlN, and InN, and their alloys and heterostructures have been investigated extensively in the last 3 decades, leading to several technologically successful photonic and electronic devices. Just over the past few years, a number of "new" nitride materials have emerged with exciting photonic, electronic, and magnetic properties. Some examples are 2D and layered hBN and the III-V diamond analog cBN, the transition metal nitrides ScN, YN, and their alloys (e.g. ferroelectric ScAlN), piezomagnetic GaMnN, ferrimagnetic Mn4N, and epitaxial superconductor/semiconductorNbN/GaN heterojunctions. This article reviews the fascinating and emerging physics and science of these new nitride materials. It also discusses their potential applications in future generations of devices that take advantage of the photonic and electronic devices eco-system based on transistors, light-emitting diodes, and lasers that have already been created by the nitride semiconductors.

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