Ultra-broadband, self-powered and high performance vertical WSe2/AlOx/Ge heterojunction photodetector with MXene electrode

Abstract

Two-dimensional materials/bulk semiconductor vertical van der Waals heterojunction are of great importance for high performance photodetector. However, their actualization are still impeded by their relatively narrow response range and large amounts of interfacial defects. Herein, in light of the excellent optoelectronic properties of WSe2 and Ge, we design a kind of self-powered vertical WSe2/AlOx/Ge heterojunction photodetector with MXene top electrode by simply stacking Ti3C2Tx MXene and WSe2 thin film on the AlOx/Ge substrate. The device enables an ultra-broadband spectral response from 405 nm to 3800 nm (mid-wave infrared light) because of the plasmon-induced hot electrons in the Ti3C2Tx MXene film. Also, the device proves the distinguished photodetection performance in terms of a large responsivity of ∼ 1088 mA/W, a high specific detectivity of ∼ 1.17 × 1012 Jones at 980 nm, and a fast response time of 43/63 μs. The vertical stacking structure, the introduction of passivation layer and MXene electrode are considered to be new strategies of designing heterojunction for ultra-broadband, low-power consumption and high performance next-generation photodetector.