Abstract: In this paper, porous n-GaN thin films with a pore density of 1.51×10¹⁰ cm^-2 and an average pore size of 38 nm were initially prepared by UV-assisted electrochemical etching (UV-EC). Subsequently, a series of Zn_xCu_1-xS composite films, with x values of 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, were deposited on the porous n-GaN films by water bath method. The bandgaps of the porous n-GaN/Zn_xCu_1-xS heterojunctions varied in the range from 2.34 eV to 3.51 eV. Hall test results demonstrate that when x values is less than 1, the Zn_xCu_1-xS composite films exhibit p-type semiconductor properties. Furthermore, increasing the proportion of CuS leads to an improvement in the conductivity of the composite films. Additionally, XPS results confirm that both Cu and Zn possess a +2 valence within the composite films. When Zn_xCu_1-xS forms a heterojunction with porous n-GaN, the energy band structures of both materials interact to create a built-in electric field. This field facilitates the efficient separation of photogenerated electron-hole pairs. Finally, p-n heterojunctions UV detectors were constructed based on these heterostructures. The I-V curve results indicate that these detectors exhibit good rectification characteristics. Notably, the n-GaN/p-Zn_0.4Cu_0.6S detector demonstrates optimal performance. In the dark state, I_{+3 V}/I_{-3 V} is approximately 1.78×10⁵. Under a bias voltage of -3 V and an optical power density of 432 μW/cm² (ultraviolet light at 365 nm), this detector’s photo-to-dark current ratio exceeds 10³, the rise/fall time is 0.09/39.8 ms, responsivity(R) reaches 0.352 A/W, the external quantum efficiency (EQE) stands at 119.6%, and detectivity(D^*) is 3.21×10¹² Jones. The I-t curve results indicate that the porous n-GaN/p-Zn_xCu_1-xS heterojunctions UV detector possesses reproducible performance during the consecutive on-off optical cycling process with reproducible photocurrent response. This study offers valuable theoretical insights and a comprehensive understanding of the physical properties and performance characteristics of these novel heterostructures UV detectors.

Key words: p-Zn_xCu_1-xS, porous n-GaN, heterojunction, ultraviolet detector, photo-to-dark current ratio, responsivity