Wavelength-selective enhancement of photo-responsivity in metal-gated multi-layer MoS2 phototransistors

Abstract

The responsivities of MoS2 based photodetectors or phototransistors have been improved by integrating additional layers or implementing a hetero-structure. Despite complicated processes, these methods only improve the overall responsivity and are not capable of wavelength selective enhancement. This study reports the wavelength-selective enhancement of photo-responsivity in a multi-layer MoS2 phototransistor by employing a reflective Al metal gate. We have observed that the photo-responsivities are enhanced at a wavelength of ∼500 nm (FWHM = 140 nm) in the Al metal-gated multi-layer MoS2 phototransistors. The finite difference time domain method also confirmed that the wavelength for enhanced responsivity can be adjusted according to the thicknesses of the MoS2 and gate insulating layer. Using this effect, the Al metal-gated multi-layer MoS2 phototransistors can be tuned for specific applications.