Getting to know gallium oxide, a promising material for electronics

Unique properties of the thermodynamically stable monoclinic gallium oxide, β-Ga₂O₃, make it a promising material for new generation electronics, especially in power electronics. β-Ga₂O₃ has a wide bandgap, allowing it to operate at higher voltages than its better-known competitors silicon carbide and gallium nitride. While a wide-energy bandgap usually means higher resistance and power dissipation, dopants in β-Ga₂O₃ can help maintain conductivity. β-Ga₂O₃ is also advantageous due to its availability as high quality single crystal substrates with different surface orientations, which allows for the homoepitaxial growth of thin films using techniques such as metal-organic chemical vapor deposition and molecular beam epitaxy.

Mazzolini et al. used molecular beam epitaxy to study the effect of deposition conditions of β-Ga₂O₃ thin films on (010)-oriented β-Ga₂O₃ substrates, the most investigated orientation for devices. When the authors grew the films under gallium-rich deposition conditions, they found that (110) and (-110) facets formed on the (010) oriented surface, suggesting the most thermodynamically stable surface orientation is (110) and not (010). Mazzolini et al. plan to further investigate growing thin films on (110)-oriented β-Ga₂O₃ substrates to explore possible advantages of this orientation.

The authors also applied metal-exchange catalysis, a growth mechanism recently discovered by some of the authors, to increase the growth rate of (010)-oriented β-Ga₂O₃ thin films. They found that an additional indium flux during β-Ga₂O₃ deposition increased the growth rate threefold, while maintaining a smooth surface. The authors claim that the technique could enable scientists to achieve, using molecular beam epitaxy, β-Ga₂O₃ orientations that were previously neglected due to their low growth rate.

Source: “Faceting and metal-exchange catalysis in (010) β-Ga₂O₃ thin films homoepitaxially grown by plasma-assisted molecular beam epitaxy,” by P. Mazzolini, P. Vogt, R. Schewski, C. Wouters, M. Albrecht, and O. Bierwagen, APL Materials (2018). The article can be accessed at https://doi.org/10.1063/1.5054386 .