Epitaxial NiO/Al0.5Ga0.5N heterostructures for high-performance solar-blind ultraviolet self-powered photodetectors

Abstract

Solar-blind ultraviolet (SB-UV) self-powered photodetectors (SPDs), with advantages such as high selectivity to UV light below 280 nm without the need for external power, are promising for several application areas including flame detection, environmental monitoring, space exploration, and secure communication. However, until now the performance of SB-UV SPDs has been limited by the scarcity of high-quality p-type wide-bandgap semiconductors with a high hole concentration. Here, we design, fabricate and test self-powered SB-UV photodetectors based on Li-doped NiO/Al_0.5Ga_0.5N p–n heterojunctions using pulsed laser deposition (PLD) at room temperature. By optimizing the oxygen partial pressure, we achieved epitaxial growth of NiO on AlGaN, enhancing hole migration and preserving heterointerface integrity. The resultant device demonstrated a high photodetector current ratio (PDCR = 3.12 × 10³), excellent SB-UV selectivity (R₂₅₄/R₃₆₅ = 5.78 × 10³), a low dark current (8.91 × 10⁻³ nA), and fast response time with a rise time (τ_r) of 21 ms and a fall time (τ_f) of 70 ms under zero bias, while maintaining long-term operational stability. The demonstrated self-powered SB-UV detection capability enables practical implementation in optical communication systems. Notably, the low-temperature PLD fabrication protocol shows excellent compatibility with CMOS processes, offering a viable pathway for developing flexible optoelectronic systems and hybrid integrated photonic circuits.