Preparation and ultraviolet detection performance of Cu doped b-Ga2O3 thin films *

Solar-blind UV photodetectors (SBPs) have attracted great attention because they are widely used in missile tracking, fire detection, biochemical analysis, astronomical observations, space-to-space communications, etc. At present, it is found that wide bandgap semiconductor materials such as AlxGa1-xN, Mg1Zn1-xO, diamond and 13-Ga2O3 are ideal semiconductor materials for developing high-performance SBPs. The ultra-wide band gap semiconductor material, 13-Ga2O3, has a large band gap width of 4.9 eV, strong breakdown electric field, absorption edge located in the solar blind ultraviolet band (200-280 nm), and it also has high transmittance in the near ultraviolet and the whole visible band. Therefore, 13-Ga2O3 is a very suitable material for making solar blind UV photodetectors. However, the p-type 13-Ga2O3 is difficult to dope, which limits the further development of 13-Ga2O3 devices. In this work, the 13-Ga2O3 thin films with different Cu doping content are grown on sapphire substrates by chemical vapor deposition method, and the morphology, crystal structure and optical properties of 13-Ga2O3 films are measured. The test results show that the surfaces of 13-Ga2O3 films with different Cu content are relatively smooth, and the ( ) diffraction peak positions shift toward the lower 2 over bar 01 degree side with the increase of Cu content, which indicates that Cu2+ replaces Ga3+ and enters into the 13-Ga2O3 lattice. The optical absorption spectrum measurement indicates that the energy gaps of samples are evidently narrowed with the increase of Cu doping concentration. Hall measurements indicate that the Cu doped 13-Ga2O3 thin films have a p-type conductivity with a hole concentration of 7.36 x 1014, 4.83 x 1015 and 1.69 x 1016 cm-3, respectively. In addition, a photoconductive UV detector with metal-semiconductor-metal structure is prepared by evaporating Au on a Cu-doped 13-Ga2O3 thin film, and its UV detection performance is studied. The results show that the photocurrent value of the device increases with Cu content increasing. The photo-to-dark current ratio (Il/Id) is about 3.8x102 of 2.4% Cu content device under 254 nm-wavelength light at 10 V. The rise time and decay time are 0.11 s and 0.13 s, respectively. Furthermore, the responsivity and external quantum efficiency can reach 1.72 A/W and 841% under 254 nm-wavelength light with a light intensity of 64 mu W/cm2.

Automated summary

Solar-blind UV photodetectors have wide applications in missile tracking, fire detection, biochemical analysis, astronomical observations, and space-to-space communications. This study focuses on the development of high-performance solar-blind UV photodetectors using 13-Ga2O3 thin films doped with different concentrations of Cu. The Cu-doped 13-Ga2O3 thin films exhibit improved morphology, crystal structure, and optical properties. The devices based on Cu-doped 13-Ga2O3 thin films demonstrate enhanced UV detection performance with increased Cu content.