In this paper, high quality metastable α-phase gallium oxide (α-Ga₂O₃) films were epitaxial grown on m surface sapphire substrate by pulsed laser deposition (PLD) technique. The effects of different growth temperature and oxygen partial pressure on the morphology and crystallinity of the films were studied by X-ray diffraction and scanning electron microscopy. Based on the heteroepitaxial α-Ga₂O₃ films grown under optimized conditions, a metal-semiconductor-metal (MSM) solar blind UV photodetector was fabricated. Due to the good crystal quality and few defects of the film, the device demonstrates high performances under 254 nm illumination. The device has 10^-6 A photo current and 10^-10 A dark current at 5 V bias, achieving a photodark current ratio of 10⁴. The maximum responsivity is 36.7 A/W, the maximum external quantum efficiency is 1.79×10⁴%, and the maximum detectivity is 2.45×10¹⁴ Jones.