Comparative study of photoconductive and diode MoS2/MoTe2 heterojunction infrared photodetectors

When two two-dimensional semiconductors stack and form the type-II band alignment van der Waals heterojunction, sub-bandgap photoelectric detection can be realized, thus overcoming the intrinsic bandgap limit on the working wavelength of traditional semiconductor detectors. Therefore, photodetectors based on 2D heterostructures have great potentials and advantages in infrared photoelectric detection. High-performance infrared photodetectors based on two-dimensional transition metal chalcogenide heterojunction have been widely reported. However, the current design of two-dimensional heterojunction photodetectors primarily focused on the diode, which has low carrier utilization efficiency and with no extra gain, rendering poor photo responsivities. In addition, the acquisition of monolayer MoTe₂ is difficult, and there are few researches based on monolayer MoTe₂ heterojunction devices. This work aims at a comparative analysis of photoconductive and diode MoS₂/MoTe₂ heterojunction infrared photodetectors. By assessing the photo response of the photodetectors in both operational modes to the same infrared wavelength, our findings reveal that the photoresponsivity of the two-dimensional heterojunction detector in photoconductive mode reaches 10⁴ nA/W, which is 100 times higher than the diode under the identical conditions. In the photoconductive mode, the inherent photogating effect within the heterojunction engages electrons in the MoS₂ layer in multiple photoconductive processes before recombining with holes in the MoTe₂ layer, significantly enhancing optical gain and consequently improving responsiveness. The superior detection performance of the two-dimensional heterojunction photodetector in photoconductive mode presents a novel approach to addressing the performance limitations of infrared detectors.