Ultimate Limit in Optoelectronic Performances of Monolayer WSe<sub>2</sub> Sloping-Channel Transistors
Zhengdao Xie, Guoli Li, Shengxuan Xia, Chang Liu, Sen Zhang, Zhouxiaosong Zeng, Xingqiang Liu, Denis Flandre, Zhiyong Fan, Lei Liao, Xuming Zou
Abstract
Atomically thin monolayer two-dimensional (2D) semiconductors with natural immunity to short channel effects are promising candidates for sub-10 nm very large-scale integration technologies. Herein, the ultimate limit in optoelectronic performances of monolayer WSe 2 field-effect transistors (FETs) is examined by constructing a sloping channel down to 6 nm. Using a simple scaling method compatible with current micro/nanofabrication technologies, we achieve a record high saturation current up to 1.3 mA/μm at room temperature, surpassing any reported monolayer 2D semiconductor transistors. Meanwhile, quasi-ballistic transport in WSe 2 FETs is first demonstrated; the extracted high saturation velocity of 4.2 × 10 6 cm/s makes it suitable for extremely sensitive photodetectors. Furthermore, the photoresponse speed can be improved by reducing channel length due to an electric field-assisted detrapping process of photogenerated carriers in localized states. As a result, the sloping-channel device exhibits a faster response, higher detectivity, and additional polarization resolution ability compared to planar micrometer-scale devices.