Beta-gallium oxide (β-Ga2O3) thin films were deposited on c-plane (0001) sapphire substrates with different mis-cut angles along < > by metal-organic chemical vapor deposition (MOCVD). The structural properties and surface morphology of as-grown β-Ga2O3 thin films were investigated in detail. It was found that by using thin buffer layer and mis-cut substrate technology, the full width at half maximum (FWHM) of the ( ) diffraction peak of the β-Ga2O3 film is decreased from 2° on c-plane (0001) Al2O3 substrate to 0.64° on an 8° off-angled c-plane (0001) Al2O3 substrate. The surface root-mean-square (RMS) roughness can also be improved greatly and the value is 1.27 nm for 8° off-angled c-plane (0001) Al2O3 substrate. Room temperature photoluminescence (PL) was observed, which was attributed to the self-trapped excitons formed by oxygen and gallium vacancies in the film. The ultraviolet–blue PL intensity related with oxygen and gallium vacancies is decreased with the increasing mis-cut angle, which is in agreement with the improved crystal quality measured by high resolution X-ray diffraction (HR-XRD). The present results provide a route for growing high quality β-Ga2O3 film on Al2O3 substrate.

Heavy doped n-type ˇ-Ga 2 O 3 (HD-Ga 2 O 3 ) was obtained by employing Si ion implantation technology on unintentionally doped ˇ-Ga 2 O 3 single crystal substrates. To repair the Ga 2 O 3 lattice damage and activate the Si after implantation, the implanted substrates were annealed at 950 ı C, 1000 ı C, and 1100 ı C, respectively.High-resolution X-ray diffraction and high-resolution transmission electron microscopy show that the ion-implanted layer has high lattice quality after high-temperature annealing at 1000 ı C. The minimum specific contact resistance is 9:2 10 5 cm 2 , which is attributed to the titanium oxide that is formed at the Ti/Ga 2 O 3 interface via rapid thermal annealing at 480 ı C. Based on these results, the lateral ˇ-Ga 2 O 3 diodes were prepared, and the diodes exhibit high forward current density and low specific on-resistance.

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