Abstract
We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow β-Ga2O3 at a growth rate of ∼1 μm/h with control of the silicon doping concentration from 5 × 1016 to 1019 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 β-Ga2O3 by conventional MBE. As a result, a growth rate of ∼1 μm/h is readily achieved at a relatively low growth temperature (Tsub ≈ 525 °C), resulting in films with high structural perfection and smooth surfaces (rms roughness of <2 nm on ∼1 μm thick films). Silicon-containing oxide sources (SiO and SiO2) producing an SiO suboxide molecular beam are used to dope the β-Ga2O3 layers. Temperature-dependent Hall effect measurements on a 1 μm thick film with a mobile carrier concentration of 2.7 × 1017 cm-3 reveal a room-temperature mobility of 124 cm2 V-1 s-1 that increases to 627 cm2 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 β-Ga2O3 films grown by S-MBE at growth rates of ∼1 μm/h.
| Original language | English |
|---|---|
| Article number | 041102 |
| Journal | APL Materials |
| Volume | 11 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 1 2023 |
| Externally published | Yes |
Funding
K.A., C.A.G., N.A.P., J.S., J.P.M., D.J., H.G.X., D.A.M., M.O.T., H.P.N., and D.G.S. acknowledge the support from the AFOSR/AFRL ACCESS Center of Excellence under Award No. FA9550-18-1-0529. J.P.M. also acknowledges the support from the National Science Foundation within a Graduate Research Fellowship under Grant No. DGE-1650441. P.V. and Y.A.B. acknowledge the support from ASCENT, one of six centers in JUMP, a Semiconductor Research Corporation (SRC) program sponsored by DARPA. F.V.E.H. acknowledges the support from the Alexander von Humboldt Foundation in the form of a Feodor Lynen fellowship. F.V.E.H. also acknowledges the support from the National Science Foundation (NSF) [Platform for the Accelerated Realization, Analysis and Discovery of Interface Materials (PARADIM)] under Cooperative Agreement No. DMR-1539918. M.D.W., D.A.M., and D.G.S. acknowledge the support from the NSF under DMR-2122147. M.D.W. also acknowledges NSF Grant No. HRD-1924204 and ONR Award No. N00014-21-1-2823. This work made use of the Cornell Center for Materials Research (CCMR) Shared Facilities, which are supported through the NSF MRSEC Program (Grant No. DMR-1719875). The substrate preparation was performed, in part, at the Cornell NanoScale Facility, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the NSF (Grant No. NNCI-2025233). This work also made use of the Cornell Energy Systems Institute Shared Facilities partly sponsored by the NSF (Grant No. MRI DMR-1338010).