Ultrasensitive Phototransistor Based on Laser-Induced P-Type Doped WSe2/MoS2 Van der Waals Heterojunction

Abstract

Out-of-plane p-n heterojunctions based on two-dimensional layered materials (2DLMs) with unusual physical characteristics are attracting extensive research attention for their application as photodetectors. However, the present fabrication method based on 2DLMs produces out-of-plane p-n homojunction devices with low photoresponsivity and detectivity. This work reports an ultrasensitive phototransistor based on a laser-induced p-doped WSe2/MoS2 van der Waals heterojunction. The laser treatment is used for p-doping WSe2 nanoflakes using high work function WOx. Then, an n-type MoS2 nanoflake is transferred onto the resulting p-doped WSe2 nanoflake. The built-in electric field of p-doped WSe2/MoS2 is stronger than that of pristine WSe2/MoS2. The p-n junction between p-doped WSe2 and MoS2 can separate more photogenerated electron–hole pairs and inject more electrons into MoS2 under laser illumination than pristine WSe2/MoS2. Thus, a high photoresponsivity (R) of ~1.28 × 105 A·W−1 and high specific detectivity (D*) of ~7.17 × 1013 Jones are achieved under the illumination of a 633 nm laser, which is approximately two orders higher than the best phototransistor based on a WSe2/MoS2 heterojunction. Our work provides an effective and simple method to enhance photoresponsivity and detectivity in two-dimensional (2D) heterojunction phototransistors, indicating the potential applications in fabricating high-performance photodetectors based on 2DLMs.

Realization of High Current Gain for Van der Waals MoS2/WSe2/MoS2 Bipolar Junction Transistor

“…For the WSe 2 flake, it presents two Raman peaks centered at 249.8 cm −1 and 258.1 cm −1 , consistent with previous works [26][27][28]. In addition, the Raman peaks in the MoS 2 /WSe 2 overlapped region are consistent with the individual MoS 2 and WSe 2 sheets, indicating the successful preparation of the high-quality van der Waals heterostructure [29,30]. It should be noted that an appropriate increase in the thickness of the MoS 2 and n + -MoS 2 can improve the contact quality between 2D materials and metal electrodes, as shown in Figures S1 and S2 of the Supplementary Materials.…”

AC Characteristics of van der Waals Bipolar Junction Transistors Using an MoS2/WSe2/MoS2 Heterostructure

“…The peaks at 249.8 and 258.3 cm −1 for the WSe 2 flake are ascribed to the E 1 2g mode and the A 1g mode [30]. In addition, the Raman spectra of the three flake overlap region are the sum of the Raman peaks of the MoS 2 and WSe 2 flakes, thereby confirming the successful fabrication of the vertically stacked heterostructure [31].…”