【International Papers】Investigation on the Mist Intensity to Deposit Gallium Oxide Thin Films by Mist Chemical Vapor Deposition

      Researchers from the De Montfort University have published a dissertation titled " Investigation on the Mist Intensity to Deposit Gallium Oxide Thin Films by Mist Chemical Vapor Deposition " in Physica Status Solidi-Rapid Research Letters.

Abstract

      In this study, a novel, simple, and robust mist chemical vapor deposition is demonstrated, compatible with existing industrial practices to deposit gallium oxide thin films and influence of mist intensity on the properties of gallium oxide. The intensity of the mist generation is optimized to obtain smooth and uniform thin films. The thin film deposited in this work is mixed phase polycrystalline gallium oxide. Ultraviolet–visible–near-infrared spectroscopy and photo response of thin film unveil that gallium oxide thin film is responsive to ultraviolet wavelengths including deep ultraviolet-C and ultraviolet-B bands and the mist-generation intensity has negligible influence on the bandgap of the thin film. Thickness of thin film can be altered by varying the mist intensity. It is observed that there is no appreciable impact on refractive index of varying mist intensity. Morphological studies prove the formation of ultrasmooth thin film with root mean square value of 0.628 nm; which is closer and/or better than conventional semiconductor thin-film deposition processes used for depositing Ga₂O₃.

Figure 1 a) Mist chemical vapor deposition (M-CVD) instrumentation setup consisted of mist-generation unit, reaction area, mist controller unit, heating source, and exhaust for carrier gas. The mist-generation unit and quartz tube-based reaction unit are coupled together using Union and O rings. b,c) Mist generated from precursor liquid carried by carrier gas was coming out of mist outlet and it formed mist streamline before dispersing into the air.

Figure 2 a) Ultraviolet–visible–near-infrared (UV–vis—NIR) spectra exhibited blueshift of absorption edge with increase in the mist intensity; most prominent for 100% mist intensity. The direct bandgap analysis using Tauc method (inset graph) showed the increase in bandgap with the increase in mist intensity. b) Increase in the bandgap of Ga₂O₃thin film with increase in the mist intensity, which may be attributed to the change in stoichiometry of the thin film at higher intensities.

Paper Link：https://doi.org/10.1002/pssr.202300296