Chlorine-Infused Wide-Band Gap p-CuSCN/n-GaN Heterojunction Ultraviolet-Light Photodetectors

Abstract
Copper thiocyanate (CuSCN) is a p-type semiconductor that exhibits hole-transport and wide-band gap (∼3.9 eV) characteristics. However, the conductivity of CuSCN is not sufficiently high, which limits its potential application in optoelectronic devices. Herein, CuSCN thin films were exposed to chlorine using a dry etching system to enhance their electrical properties, yielding a maximum hole concentration of 3 × 1018 cm–3. The p-type CuSCN layer was then deposited onto an n-type gallium nitride (GaN) layer to form a prototypical ultraviolet-based photodetector. X-ray photoelectron spectroscopy further demonstrated the interface electronic structures of the heterojunction, confirming a favorable alignment for holes and electrons transport. The ensuing p-CuSCN/n-GaN heterojunction photodetector exhibited a turn-on voltage of 2.3 V, a responsivity of 1.35 A/W at −1 V, and an external quantum efficiency of 5.14 × 102% under illumination with ultraviolet light (peak wavelength of 330 nm). The work opens a new pathway for making a plethora of hybrid optoelectronic devices of inorganic and organic nature by using p-type CuSCN as the hole injection layer.

Citation
Liang, J.-W., Firdaus, Y., Kang, C. H., Min, J.-W., Min, J.-H., Al Ibrahim, R. H., Wehbe, N., Hedhili, M. N., Kaltsas, D., Tsetseris, L., Lopatin, S., Zheng, S., Ng, T. K., Anthopoulos, T. D., & Ooi, B. S. (2022). Chlorine-Infused Wide-Band Gap p-CuSCN/n-GaN Heterojunction Ultraviolet-Light Photodetectors. ACS Applied Materials & Interfaces. https://doi.org/10.1021/acsami.1c22075

Acknowledgements
This research was supported by King Abdullah University of Science and Technology (KAUST) baseline funding (BAS/1/1614-01-01), MBE equipment funding (C/M-20000-12-001-77), and MBE equipment funding (KCR/1/4055-01-01).
JWM, TKN, and OBS gratefully acknowledge King Abdulaziz City for Science and Technology (KACST) for funding the Technology Innovation Center on Solid-State Lighting at KAUST under Grant no. KACST TIC R2-FP-008.
The authors further acknowledge the Nanofabrication Core Lab, Imaging and Characterization Core Lab, as well as the Solar Center Device Fabrication Lab at KAUST.
Part of this work was supported by King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under award nos: OSR-2018-CARF/CCF-3079 and OSR-2019-CRG8-4095.3.
The DFT calculations used computational time granted from GRNET in the National HPC facility, ARIS, under project 11013-CREATE.

Publisher
American Chemical Society (ACS)

Journal
ACS Applied Materials & Interfaces

DOI
10.1021/acsami.1c22075

Additional Links
https://pubs.acs.org/doi/10.1021/acsami.1c22075

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