Record-high Work-function p-Type CuBiP 2 Se 6 Atomic Layers for High-photoresponse van der Waals Vertical Heterostructure Phototransistor.

The notable lack of intrinsic p-type two-dimensional (2D) layered semiconductors has hindered the engineering of 2D devices for complementary metal oxide semiconductors (CMOSs). Herein, a novel quaternary intrinsic p-type 2D semiconductor, CuBiP 2 Se 6 atomic layers, was introduced into 2D family. The semiconductor displayed a high work function of 5.26 eV, a moderate hole mobility of 1.72 cm 2 V -1 s -1 , and an ultra-high on/off current exceeding 10 6 at room temperature. To date, 5.26 eV is the highest work-function recorded in p-type 2D materials, indicating the ultra-stable p-type behaviour of CuBiP 2 Se 6 . Additionally, we designed and fabricated a multilayer graphene/CuBiP 2 Se 6 /multilayer graphene (MLG/CBPS/MLG)-based fully vertical van der Waals heterostructure phototransistor. This device exhibited outstanding optoelectronic performance with a responsivity (R) of 4.9 × 10 4 A/W, an external quantum efficiency (EQE) of 1.5 × 10 7 %, a detectivity (D) of 1.14 × 10 13 Jones and a broad working wavelength (400-1100 nm), respectively. This was comparable to state-of-the-art 2D devices. We attributed such excellent performance to the ultrashort transmit length and non-destructive/defect-free contacts. This led to faster response speed and eliminated Fermi-level pinning effects. Moreover, ultrahigh responsivity and detectivity endowed our device with applaudable imaging sensing capability. These results make CuBiP 2 Se 6 an ideal p-type candidate material for next-generation CMOSs logic devices. This article is protected by copyright. All rights reserved.