Ga2O3 has gained intensive attention for the continuing myth of the electronics as a new-generation wide bandgap semiconductor, owing to its natural physical and chemical properties. In this review article, we selectively summarized the recent advances on the experimental and theoretical demonstration of β-Ga2O3-based power devices, including Schottky barrier diodes and field-effect transistors, aiming for an inherent comprehending of the operating mechanisms, discussion on the obstacles to be addressed, and providing some comprehensive guidance for further developments. In the short run, Ga2O3 may well be promising to lead power electronics. 

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β-Ga2O3-Based Power Devices: A Concise Review

First Demonstration of Hetero-epitaxial ε-Ga2O3 MOSFETs by MOCVD and a F-plasma Surface Doping

Heteroepitaxy of ε-Ga2O3 thin films grown on AlN/Si(1 1 1) templates by metal–organic chemical vapor deposition

Phase and microstructural evolution of gallium oxide (Ga2O3) films grown on vicinal (0001) sapphire substrates was investigated using a suite of analytical tools. High-resolution transmission electron microscopy and scanning transmission electron microscopy of a film grown at 530 °C revealed the initial pseudomorphic growth of three to four monolayers of α-Ga2O3, a 20–60 nm transition layer that contained both β- and γ-Ga2O3, and a top ∼700 nm-thick layer of phase-pure κ-Ga2O3. Explanations for the occurrence of these phases and their sequence of formation are presented. Additional growths of Ga2O3 films in tandem with x-ray diffraction and scanning electron microscopy investigations revealed that the top layer varied in phase composition between ∼100% κ-Ga2O3 and ∼100% β-Ga2O3; the surface microstructure ranged from poorly coalesced to completely coalesced grains as a function of growth temperature, growth rate, or diluent gas flow rate. In general, it was found that the κ-phase is favored at lower growth temperatures and higher triethylgallium flow rates (low VI/III ratios). The growth of nominally single-phase κ-Ga2O3 within the top layer was observed in a temperature range between 500 and 530 °C. Below 470 °C, only amorphous Ga2O3 was obtained; above 570 °C, only the β-phase was deposited. 

Layered phase composition and microstructure of κ-Ga2O3-dominant heteroepitaxial films grown via MOCVD

Here, we report on heteroepitaxial α-Ga2O3 MOSFETs with a breakdown voltage (BV) of 2.3 kV at a specific on-resistance of 335 mΩ cm2. High-quality α-Ga2O3 layers were grown on a sapphire substrate via halide vapor-phase epitaxy (HVPE). A stack of Ti/Al/Ni/Au was used for the S/D electrode, exhibiting significantly reduced contact resistance as compared with a conventional Ti/Au stack. Consequently, the record BV and mobility of 20.4 cm2 V−1 s−1 were achieved. Moreover, a consistent critical field of 1 MV cm−1 was obtained for variable LGD. Our results are superior to recently reported heteroepitaxial α-/β-Ga2O3 MOSFETs, which is promising toward HVPE α-Ga2O3 based power devices.

Ryubin Park

Papers

Fluorine-based plasma treatment for hetero-epitaxial β-Ga2O3 MOSFETs