High-performance MSM UV photodetector based on a NiO/InGaO type-II p–n heterojunction with mitigated PPC effect

Based on a strategically designed NiO/InGaO type-II p–n heterojunction (NIH) architecture, this work presents a high-performance metal–semiconductor–metal ultraviolet photodetector (UVPD). The top-layer n-InGaO (IGO) film, featuring heavy doping-induced carrier degeneracy that positions the Fermi level near the conduction band minimum, establishes an ideal Ohmic contact with Au interdigital electrodes through efficient quantum tunneling. This configuration ensures barrier-free charge extraction and significantly augments photoconductive gain through self-trapped holes localized at abundant oxygen vacancies of IGO. Coupled with the underlying p-type NiO layer, the structure forms a p–n heterojunction that constructs a robust built-in electric field (Ebi), enabling efficient separation of photo-generated electron–hole pairs and suppressing trap-assisted recombination. Notably, this Ebi efficiently mitigates the persistent photoconductivity effect intrinsic to oxide semiconductors. Benefiting from this optimized energy band engineering and interfacial design, the fabricated NIH UVPD achieves a remarkable responsivity of 1.82 × 104 A/W and an exceptional external quantum efficiency of 8.07 × 106% at 5 V under 280 nm illumination, demonstrating great potential for high-performance UV detection.