An Asymmetry Field‐Effect Phototransistor for Solving Large Exciton Binding Energy of 2D TMDCs

作者：Hyun‐Soo Ra, Jongtae Ahn, Jisu Jang, Tae Wook Kim, Seung Ho Song, Min‐Hye Jeong, Sang‐Hyeon Lee, Taegeun Yoon, Tae Woong Yoon, Seungsoo Kim, Takashi Taniguch, Kenji Watanabe, Young Jae Song, Jong‐Soo Lee, Do Kyung Hwang · 发表于：Advanced Materials · 年份：2021 · DOI：10.1002/adma.202107468 · 被引用次数：13 · 研究领域：2D Materials and Applications、Perovskite Materials and Applications、MXene and MAX Phase Materials

Abstract The probing of fundamental photophysics is a key prerequisite for the construction of diverse optoelectronic devices and circuits. To date, though, photocarrier dynamics in 2D materials remains unclear, plagued primarily by two issues: a large exciton binding energy, and the lack of a suitable system that enables the manipulation of excitons. Here, a WSe 2 ‐based phototransistor with an asymmetric split‐gate configuration is demonstrated, which is named the “asymmetry field‐effect phototransistor” (AFEPT). This structure allows for the effective modulation of the electric‐field profile across the channel, thereby providing a standard device platform for exploring the photocarrier dynamics of the intrinsic WSe 2 layer. By controlling the electric field, this work the spatial evolution of the photocurrent is observed, notably with a strong signal over the entire WSe 2 channel. Using photocurrent and optical spectroscopy measurements, the physical origin of the novel photocurrent behavior is clarified and a room‐temperature exciton binding energy of 210 meV is determined with the device. In the phototransistor geometry, lateral p–n junctions serve as a simultaneous pathway for both photogenerated electrons and holes, reducing their recombination rate and thus enhancing photodetection. The study establishes a new device platform for both fundamental studies and technological applications.