Fabrication and characterization of ultraviolet detector based on epitaxial Ta-doped Zn2SnO4 films

Zn2SnO4 films with Ta concentrations from 0 to 5% were deposited on MgO(100) substrates via pulsed laser deposition, and annealed in air atmosphere at 800 degrees C. The structure, surface morphology, optical and electrical properties of the films were systematically studied. The obtained films were inverse-spinel phase Zn2SnO4 grown along [100] orientation and the crystal quality decreased with Ta content. All the Ta-doped Zn2SnO4 films exhibited high average transmittances of about 95% in visible region with optical band gaps ranging from 3.98 to 4.10 eV. The metal-semiconductor-metal ultraviolet (UV) detector fabricated using the 3% Ta-doped Zn2SnO4 film exhibited the best detection performance with high photoresponsivity in wavelength range of 200-280 nm. The photoresponsivity at 254 nm was 23.3 A/W and the photo-dark current ratio exceeded 104 at 5 V bias. The Zn2SnO4-based detectors also showed good repeatability of UV detection.