Investigation of Highly Efficient Dual-Band Photodetector Performance of Spin-on-Doping (SOD) Grown p-Type Phosphorus Doped ZnO (P:ZnO)/n-Ga $_{\text{2}}$ O $_{\text{3}}$ Heterojunction Device

We developed a stable and reproducible p-type P:ZnO thin film using a cost-effective solution-derived spin-on-doping (SOD) technique. We created a pure p-n heterojunction by depositing a highly transparent Ga $_{\text{2}}$ O $_{\text{3}}$ thin film on P:ZnO for photodetector applications. The films’ surface morphology and thickness were analyzed using AFM and FEGSEM. At the same time, UV-visible (UV–Vis) and PL spectroscopy were employed to investigate their optical properties, including absorption, energy bandgap, and defect-related carrier transitions. The resulting P:ZnO/Ga $_{\text{2}}$ O $_{\text{3}}$ heterojunction demonstrated excellent photo-response performance, with a responsivity of 4.76 A/W, detectivity of 10.13 $\times$ 10 $^{\text{12}}$ Jones, and rapid response speed. The device exhibited sensitivity to UV-C and UV–Vis wavelength regions, showcasing its potential for high-performance, dual-band, and low-power photodetectors.