Silicon-doped β-Ga2O3 films grown at 1 μm/h by suboxide molecular-beam epitaxy

We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow beta-Ga2O3 at a growth rate of similar to 1 mu m/h with control of the silicon doping concentration from 5 x 10(16) to 10(19) cm(-3). In S-MBE, pre-oxidized gallium in the form of a molecular beam that is 99.98% Ga2O, i.e., gallium suboxide, is supplied. Directly supplying Ga2O to the growth surface bypasses the rate-limiting first step of the two-step reaction mechanism involved in the growth of beta-Ga2O3 by conventional MBE. As a result, a growth rate of similar to 1 mu m/h is readily achieved at a relatively low growth temperature (T-sub approximate to 525 degrees C), resulting in films with high structural perfection and smooth surfaces (rms roughness of <2 nm on similar to 1 mu m thick films). Silicon-containing oxide sources (SiO and SiO2) producing an SiO suboxide molecular beam are used to dope the beta-Ga2O3 layers. Temperature-dependent Hall effect measurements on a 1 mu m thick film with a mobile carrier concentration of 2.7 x 10(17) cm(-3) reveal a room-temperature mobility of 124 cm(2) V-1 s(-1) that increases to 627 cm(2) V-1 s(-1) at 76 K; the silicon dopants are found to exhibit an activation energy of 27 meV. We also demonstrate working metal-semiconductor field-effect transistors made from these silicon-doped beta-Ga2O3 films grown by S-MBE at growth rates of similar to 1 mu m/h. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

We demonstrate the use of suboxide molecular-beam epitaxy (S-MBE) to successfully grow beta-Ga2O3 at a growth rate of approximately 1 μm/h with controlled silicon doping concentration. By directly supplying Ga2O to the growth surface, S-MBE bypasses the rate-limiting step in conventional MBE, resulting in high-quality films with smooth surfaces. The silicon-doped beta-Ga2O3 films grown by S-MBE show promising properties for metal-semiconductor field-effect transistors.