MOCVD-grown α-Ga2O3 with increased growth rate and improved crystal quality for deep UV optoelectronics application

α-Ga2O3 films with a more than threefold increase in growth rate were epitaxially grown on m-Al2O3 at 530 °C by employing a 700 °C high-temperature buffer layer (HTBL) in metal–organic chemical vapor deposition growth. The underlying mechanism of the enhanced growth was understood experimentally by the surface analysis and theoretically by a model based on Gibbs–Thomson equation and first-principles calculations. With HTBL, the crystal quality of the α-Ga2O3 was also significantly improved, as evidenced by the decreased x-ray diffraction rocking curve linewidth of the (303¯0) peak. The linewidth is down to 0.387°, which is significantly narrower than 0.592° from sample without HTBL. The surface morphology of HTBL features larger, more sparsely distributed islands, resulting in a lower chemical potential on the surface, which promotes the adsorption of Ga2O3-clusters by reducing the desorption and thus increases the growth. x-ray photoelectron spectroscopy showed more oxygen vacancies (Vo) on the HTBL surface. First-principles calculations indicated that Vo in the (303¯0)-surface reduced the adsorption energy from −5.48 to −6.61 eV, thereby promoting cluster adsorption. A solar-blind ultraviolet photodetector based-on α-Ga2O3 exhibited an ultra-low dark current of 0.1 pA at 10 V, a high light-to-dark current ratio of 106, a responsivity of 0.54 A/W, and a detectivity of 5.5 × 1012 Jones.