Abstract
We report on the impacts of oxygen radical ambient for (AlGa)2O3 films grown on sapphire substrates by pulsed laser deposition (PLD). All the films showed a monoclinic crystal structure and high transmittance in the ultraviolet and visible wavelength range. The surface roughness was less than 3 nm for all films, and the surface morphology has changed by applying oxygen radical ambient. The growth rate was faster in oxygen radical ambient compared with conventional oxygen ambient. Oxygen radical ambient has influences on the crystal quality of the (AlGa)2O3 films. The Ga content in β-(AlGa)2O3 films grown with oxygen plasma assistance was higher than that without the oxygen plasma, indicating the suppression of the re-evaporation of Ga related species from the film surface by plasma assistance during the PLD process.
Highlights
Wide bandgap semiconductors have been widely used in high temperature, high power, and high voltage device applications due to their large bandgap, high breakdown voltage, and stable chemical and physical properties.1,2 (AlGa)2O3 has recently emerged as a promising candidate for deep ultraviolet optoelectronic device applications because (AlGa)2O3 has an advantage of large tunable bandgaps from 4.8 eV (Ga2O3) to 8.6 eV (Al2O3) at room temperature.3–6 Lateral field-effect transistors,7 high-power modulation doped field-effect transistors,8 and solar-blind photoreactors9,10 based on (AlGa)2O3 films have been demonstrated recently.Various growth techniques, such as molecular beam epitaxy,11,12 mist chemical vapor deposition,4 sputtering,10 metalorganic chemical vapor deposition,13 and pulsed laser deposition (PLD),5,14,15 have been explored to obtain (AlGa)2O3 films
We found that oxygen radical ambient has influences on the surface morphology, crystal quality, growth rate, and the optical properties of the (AlGa)2O3 films
We have demonstrated the effects of oxygen radical ambient for (AlGa)2O3 films grown on sapphire substrates
Summary
Wide bandgap semiconductors have been widely used in high temperature, high power, and high voltage device applications due to their large bandgap, high breakdown voltage, and stable chemical and physical properties.1,2 (AlGa)2O3 has recently emerged as a promising candidate for deep ultraviolet optoelectronic device applications because (AlGa)2O3 has an advantage of large tunable bandgaps from 4.8 eV (Ga2O3) to 8.6 eV (Al2O3) at room temperature.3–6 Lateral field-effect transistors,7 high-power modulation doped field-effect transistors,8 and solar-blind photoreactors9,10 based on (AlGa)2O3 films have been demonstrated recently.Various growth techniques, such as molecular beam epitaxy,11,12 mist chemical vapor deposition,4 sputtering,10 metalorganic chemical vapor deposition,13 and pulsed laser deposition (PLD),5,14,15 have been explored to obtain (AlGa)2O3 films. The heteroepitaxial growth of β-(AlGa)2O3 films in reactive oxygen radical ambient on the sapphire substrate was investigated. The impacts of oxygen radical ambient on the surface morphology, structural properties, and optical properties of (AlGa)2O3 films deposited by PLD were discussed in detail.
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