Raman spectroscopy of HgPSe3 thin flakes and its application to near UV-to-visible photodetectors

Abstract

This study investigates the dependence of Raman spectroscopy on the number of layers in HgPSe₃ using excitation lasers at 532 nm and 633 nm. Notably, both bulk HgPSe₃ and mechanically exfoliated thin flakes exhibit two prominent Raman peaks at 147.8 and 213.9 cm⁻¹. This observation suggests that flake thickness has an insignificant influence on the characteristic Raman spectra, indicative of a high degree of structural uniformity within the material. HgPSe₃ thin flakes are used as light-absorbing materials for photodetector (PD) devices. The fabricated PDs demonstrate remarkably low dark currents on the order of femtoamperes. Their spectral response ranges from 400 nm to 630 nm, with a well-defined cutoff around 590 nm, suggesting a bandgap of approximately 2.1 eV for HgPSe₃. Furthermore, the photodetectors achieve a response time of approximately 28 ms at a bias voltage of 5 V and an illumination wavelength of 500 nm. These promising results underscore the potential of HgPSe₃ thin films as active materials in ultraviolet-visible photodetectors.