CsCu2I3/porous GaN Heterojunctions with Enhanced Optical Absorption and Ultraviolet Photoresponse

The heterogeneous integration of lead-free metal halides with wide-bandgap semiconductors offers a highly promising route for the development of high-performance ultraviolet photodetectors. In this work, porous GaN was first prepared by a high-temperature annealing method, and CsCu2I3 was subsequently deposited by an antisolvent-assisted spin-coating method to construct a CsCu2I3/porous GaN heterojunction. Compared with the planar heterojunction, CsCu2I3 in the CsCu2I3/porous GaN heterojunction can partially penetrate into the pores of porous GaN, resulting in more intimate interfacial contact and a larger effective contact area. Compared with the planar heterojunction, the CsCu2I3/porous GaN heterojunction shows stronger XRD peaks and Raman signals, together with smaller FWHM values, suggesting slightly improved structural quality. Meanwhile, UV–Vis spectra show enhanced ultraviolet absorption, which may be associated with the porous GaN-induced increase in the effective optical path and improved optical utilization. Under 365 nm ultraviolet illumination at 0 V bias, the CsCu2I3/porous GaN heterojunction ultraviolet photodetector exhibits a light-to-dark current ratio of 7.3 × 104, a responsivity (R) of 0.162 A/W, a detectivity (D*) of 1.04 × 1013 Jones, an external quantum efficiency (EQE) of 55%, and a response time of 64 ms/75 ms. This work provides a feasible interface-engineering strategy for developing high-performance lead-free heterojunction ultraviolet photodetectors.