Abstract
Monoclinic β-Ga2O3 thin films with (-201) orientation have been fabricated at substrate temperature as low as 200 °C by using plasma assisted pulsed laser deposition. The film showed high transmittance of over 80% with clear fringes in the wavelength range from 300 to 1000 nm. Structural characterization from X-ray diffraction as well as Raman spectra analysis demonstrated the monoclinic structure of the films. β-Ga2O3 film deposited at 200 °C showed similar growth rate as well as optical bandgap values with films grown at higher temperatures from 300 to 500 °C, indicating the enhanced reaction between Ga and oxygen species during the deposition process with the assistant of plasma at low temperature. The low temperature growth of β-Ga2O3 film paves the way to be compatible with the established lithography of semiconductor microfabrication processes.
Highlights
Monoclinic β-Ga2O3 thin films with (-201) orientation have been fabricated at substrate temperature as low as 200 ○C by using plasma assisted pulsed laser deposition
Structural characterization from X-ray diffraction as well as Raman spectra analysis demonstrated the monoclinic structure of the films. β-Ga2O3 film deposited at 200 ○C showed similar growth rate as well as optical bandgap values with films grown at higher temperatures from 300 to 500 ○C, indicating the enhanced reaction between Ga and oxygen species during the deposition process with the assistant of plasma at low temperature
In our previous study of substrate temperature influence on β-Ga2O3 film in non-reactive oxygen background, the growth rate showed decreased tendency with the increasing of substrate temperatures, which has been ascribed to the reevaporation of the adsorbed spices on the surface of the substrate
Summary
Gallium oxide (Ga2O3) is a material with high physical and chemical stabilities, which has wide bandgap values about 4.9 eV. The Baliga’s figure of merit of Ga2O3 is much larger than those of SiC and GaN that are being used for high power electronics, making it uniquely suited for high power devices. Ga2O3 found potential applications such as host material for rare earth luminescence, ultraviolet detector, transparent electrode for deep-UV devices, metal-oxide-semiconductor field-effect transistor (FET), and high dielectric oxide material for FET devices. the availability of free-standing β-Ga2O3 substrates fabricated in mass using melt techniques such as Floating Zone, Edge-Defined Film-Fed Growth, and Czochralski methods has put this material the state-of-the art. Ga2O3 thin films prepared by molecular beam epitaxy (MBE), sol-gel processing, pulsed laser deposition (PLD), chemical vapor deposition, co-sputtering, metalorganic chemical vapor deposition and halide vapor phase epitaxy (HVPE) were demonstrated. Among these methods, PLD shows several advantages due to completely compositional consistency from a target to the deposited film and is especially suitable for low temperature growth of thin films for the relative high kinetic energies that the ablated species have.. We report on the crystal structure and optical properties of β-Ga2O3 films deposited at various substrate temperatures by plasma assisted PLD. Being able to deposit β-Ga2O3 film at low substrate temperature is important because it opens the possibility of cointegration with complementary-metal oxide-semiconductor architecture since the maximum temperature acceptable during the device fabrication is 450 ○C.31
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