Pulsed Laser Deposition And Properties Of Sulfur / Selenium Doped Gallium Oxide Thin Films

β-Ga₂O₃has ultra-wide direct band gap（～4.9 e V）and good thermal and chemical stability.It is expected to be used in ultraviolet photodetectors and high-power electronic devices,so it has received extensive attention in recent years.Althoughβ-Ga₂O₃has an ultra-wide direct band gap,its band gap still needs to be further regulated to meet its important needs in the application of optoelectronic devices at different wavelengths.Therefore,in this work,we used PLD method to introduce S and Se elements to modify theβ-Ga₂O₃film and adjust its band gap.The main research contents and results of this work are as follows:（1）A series of Ga₂(O_1-xS_x)₃ternary alloy films were prepared by PLD at 700°C under different oxygen pressures（0 Pa～8 Pa）using Ga₂S₃ceramic as target and c-plane sapphire as substrate.A thorough examination of the crystal structure,surface morphology,film thickness,chemical makeup,and optical characteristics of the films was conducted.Furthermore,a metal-semiconductor-metal（MSM）UV photodetector was constructed by plating parallel gold electrodes on the film surface,and the photoelectric detection performance of the device was tested.The results show that the Ga₂(O_1-xS_x)₃alloy films’prepared under different oxygen pressures have good crystal quality and uniform surface grain distribution.The S content x in Ga₂(O_1-xS_x)₃thin films decreases from 0.89 to 0.03 as oxygen pressure rises,while the optical band gap increases from 3.77 e V to 5.05 e V,which is in line with the_<sup>Ga OS=4.95-3.36x+2.53x²function.The detector based on the film grown under 2 Pa oxygen pressure has a relatively high light-to-dark current ratio（596.4）,a fast response speed(τ_r1/τ_d1:0.01 s/0.03 s,τ_r2/τ_d2:0.04 s/1.04 s),and a peak responsivity of 2.1 m A/W at the wavelength of345 nm.（2）Considering that the lattice structure of MgO with cubic structure andβ-Ga₂O₃has a higher matching degree,which is expected to reduce the crystal defects in the film.Using PLD,a series of Ga₂(O_1-xS_x)₃ternary alloy films were prepared on MgO（100）substrate,with a Ga₂S₃ceramic sheet as the target,at a fixed growth temperature（600°C）and varying deposition oxygen pressures（0 Pa～6 Pa）.Systematically characterized were the films’crystal structure,surface morphology,film thickness,chemical composition,and optical properties.The results demonstrate that the film grown at low oxygen pressures（0 Pa,0.5 Pa and 1 Pa）is a single-phase S-rich Ga₂(O_1-xS_x)₃film.The Ga₂(O_1-xS_x)₃film’s surface is relatively smooth,with a root mean square roughness ranging from 0.94 nm to 4.94 nm.As the oxygen pressure increases from 0 Pa to 6 Pa,the S content x in the Ga₂(O_1-xS_x)₃film decreases monotonically from 0.83 to 0.12,while the optical band gap of the film shows a non-monotonic change,which decreases from 3.57 e V to 3.52 e V and then gradually increases to 4.72 e V,which is in line with the_<sup>Ga OS=5.04-5.34x+3.03x²function..（3）Considering that selenium（Se）is in the same main group with S and O elements,this work is the first to explore Se doped Ga₂O₃;a series of Ga₂(O_1-xSe_x)₃ternary alloy films were prepared by PLD method at a fixed growth temperature（600°C）and different oxygen pressures（0 Pa～10 Pa）using self-made Ga₂Se₃ceramic sheet as target and c-plane sapphire as substrate.Systematic characterization of the films’crystal structure,surface morphology,film thickness,chemical composition,and optical properties revealed that with an augmentation of oxygen pressure,the Se-rich Ga₂(O_1-xSe_x)₃phase gradually transmutes into the O-rich Ga₂(O_1-xSe_x)₃phase.The film surface’s root mean square roughness rose from 2.66 nm to 6.63nm,while Se content x in the film decreased from 0.96 to 0.02.Gradually,the film’s optical band gap increased from 2.74 e V to 4.95 e V,as per the_<sup>Ga OSe=5.04-5.34x+3.03x²equation.