Optical and structural properties of Si doped $\beta$-Ga${}_2$O${}_3$ (010) thin films homoepitaxially grown by halide vapor phase epitaxy

Abstract

We report the optical, electrical, and structural properties of Si doped $\beta$-Ga${}_2$O${}_3$ films grown on (010)-oriented $\beta$-Ga${}_2$O${}_3$ substrate via HVPE. Our results show that, despite growth rates that are more than one order of magnitude faster than MOCVD, films with mobility values of up to 95 cm${}^2$V${}^{-1}$s${}^{-1}$ at a carrier concentration of 1.3$\times$10${}^{17}$ cm${}^{-3}$ can be achieved using this technique, with all Si-doped samples showing n-type behavior with carrier concentrations in the range of 10${}^{17}$ to 10${}^{19}$ cm${}^{-3}$. All samples showed similar room temperature photoluminescence, with only the samples with the lowest carrier concentration showing the presence of a blue luminescence, and the Raman spectra exhibiting only phonon modes that belong to $\beta$-Ga${}_2$O${}_3$, indicating that the Ga${}_2$O${}_3$ films are phase pure and of high crystal quality. We further evaluated the epitaxial quality of the films by carrying out grazing incidence X-ray scattering measurements, which allowed us to discriminate the bulk and film contributions. Finally, MOS capacitors were fabricated using ALD HfO${}_2$ to perform C-V measurements. The carrier concentration and dielectric values extracted from the C-V characteristics are in good agreement with Hall probe measurements. These results indicate that HVPE has a strong potential to yield device-quality $\beta$-Ga${}_2$O${}_3$ films that can be utilized to develop vertical devices for high-power electronics applications.