Preparation and Properties of Wafer-Level Nanoporous GaN-Based N-Doped β-Ga ₂ O ₃ Solar-Blind Photodetectors

Wafer-level nanoporous GaN-based N-doped β-Ga2O3 (NP-GaN/N-Ga2O3) solar-blind photodetectors (PDs) are prepared by electrochemical etching and pulsed laser deposition. NP-GaN/N-Ga2O3 thin films with various N-doping concentrations exhibit the structure with [−201] orientation. After N doping, the defect-related photoluminescence (PL) intensity of NP-GaN/N-Ga2O3 is significantly weakened, indicating that N doping causes the transition of β-Ga2O3 thin films from a direct bandgap to an indirect bandgap. As the N-doping concentration increases, the defect-related PL intensity of NP-GaN/N-Ga2O3 becomes weaker due to the decreased defect density in β-Ga2O3 thin films. Compared with as-grown GaN-based N-doped β-Ga2O3 (AG-GaN/N-Ga2O3), NP-GaN/N-Ga2O3 has a weaker PL intensity, which is due to the fact that the stress relaxation and reduced defect density of NP-GaN improve the crystal quality of β-Ga2O3 thin films. The epitaxial relationship of β-Ga2O3 (−201) || GaN (0001) with β-Ga2O3 [010] || GaN [−12–10] is proved. Compared with undoped β-Ga2O3 PDs, N-doped β-Ga2O3 PDs have lower dark currents and shorter rise/decay times, which is due to the fact that N-doping reduces the density of oxygen vacancies.