Analyses of the Properties of the NiO-Doped Ga2O3 Wide-Bandgap Semiconductor Thin Films

The study began by pre-sintering Ga2O3 powder at 950 °C for 1 h, followed by the preparation of a mixture of Ga2O3 and 12 at% NiO powders to fabricate a source target material. An electron beam (e-beam) system was then used to deposit NiO-doped Ga2O3 thin films on Si substrates. X-ray diffraction (XRD) analyses revealed that the pre-sintered Ga2O3 at 950 °C exhibited β-phase characteristics, and the deposited NiO-doped Ga2O3 thin films exhibited an amorphous phase. After the deposition of the NiO-doped Ga2O3 thin films, they were divided into two portions. One portion underwent various analyses directly, while the other was annealed at 500 °C in air before being analyzed. Field-emission scanning electron microscopy (FESEM) was utilized to process the surface observation, and the cross-sectional observation was primarily used to measure the thickness of the NiO-doped Ga2O3 thin films. UV-Vis spectroscopy was used to calculate the bandgap by analyzing the transmission spectra, while the Agilent B1500A was employed to measure the I-V characteristics. Hall measurements were also performed to assess the mobility, carrier concentration, and resistivity of both NiO-doped Ga2O3 thin films. The first innovation is that the 500 °C-annealed NiO-doped Ga2O3 thin films exhibited a larger bandgap and better electrical conductivity. The manuscript provides an explanation for the observed increase in the bandgap. Another important innovation is that the 500 °C-annealed NiO-doped Ga2O3 thin films revealed a high-energy bandgap of 4.402 eV. The third innovation is that X-ray photoelectron spectroscopy (XPS) analyses of the Ga2p3/2, Ga2p1/2, Ga3d, Ni2p3/2, and O1s peaks were conducted to further investigate the reasons behind the enhanced electrical conductivity of the 500 °C-annealed NiO-doped Ga2O3 thin films.