Enhanced Deep-Ultraviolet Responsivity in Aluminum–Gallium Oxide Photodetectors via Structure Deformation by High-Oxygen-Pressure Pulsed Laser Deposition

Aluminum-gallium oxide (AGO) thin films with wide bandgaps of greater than 5.0 eV were grown using pulsed laser deposition. As evidenced by X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy, the oxygen chamber pressure considerably affected the lattice deformation in the AGO materials. Under high oxygen pressure, the lattice deformation reduced the d-spacing of the AGO(-201) plane. In the measured transmittance spectra of the AGO films, this narrowing of the d-spacing in the main plane manifested as a high-energy shift of the absorption edge. The AGO films were then installed as the active layers in the metal-semiconductor-metal photodetectors (PDs). The lattice deformation was observed to enhance the photocurrent and reduce the dark current of the device. The responsivity was 20.7 times higher in the lattice-deformed AGO-based PD sample than that in the nondeformed sample. It appeared that the lattice deformation induced the separation of the piezopotential, improving the efficiency of the photogenerated carrier recombination and, consequently, shortening the decay time of the photodetector.