First-principles study of surface kinetics in β-Ga2O3

Monoclinic β-Ga2O3 is a wide-gap (4.8 eV) semiconductor with a high breakdown field. To achieve high-quality Ga2O3 with n-type conductivity, several challenges still remain, including suboxide desorption that hinders the epitaxial growth rate and understanding the incorporation sites of Al, Si, and Sn in the Ga2O3 lattice for alloying and doping. I will discuss the origin of these challenges by unveiling the role of kinetics during the growth, including surface reconstructions under different growth conditions and adatom diffusion. Indium has been used to achieve a higher growth rate and better crystal quality during the epitaxial growth of Ga2O3. I will show the adsorption of Ga and In adatoms on the Ga2O3 (010) surface and the effect of In on the growth rate [1]. The applications of Ga2O3 in power electronics and field-effect transistors require heterostructures with a larger-gap material. As the bandgap of Al2O3 is larger than Ga2O3, there is a growing need of the epitaxial growth of (AlxGa1−x)2O3 alloys that forms heterojunctions with Ga2O3. I will show the co-adsorption of Al, Ga, and O adatoms on the Ga2O3 (010) surface reveals the role of surface reconstructions and adatom diffusion in the Al incorporation sites in the (AlxGa1−x)2O3 alloys [2,3]. Similarly, I will also discuss how surface kinetics can affect the incorporation sites of Si and Sn in β-Ga2O3, which are usually used as shallow donors that contribute the n-type conductivity of Ga2O3 [4].

[1] M. Wang, S. Mu, and C. G. Van de Walle, Phys. Rev. B 102, 035303 (2020).

[2] M. Wang, S. Mu, and C. G. Van de Walle. "Adsorption and Diffusion of Aluminum on β-Ga2O3 (010) Surfaces." ACS Appl. Mater. Interfaces, 13, 10650 (2021).

[3] J. M. Johnson, H.-L. Huang, M. Wang, S. Mu, J. B. Varley, A. A. Uddin Bhuiyan, Z. Feng, N. K. Kalarickal, S. Rajan, H. Zhao, C. G. Van de Walle, and J. Hwang, APL Mater. 9, 051103 (2021).

[4] M. Wang, S. Mu, and C. G. Van de Walle, J. Appl. Phys. 130, 185703 (2021).