Complementary MoS₂ field-effect transistor technology

Abstract

Exploring the potential of two-dimensional (2D) materials for advanced complementary field-effect transistor (FET) technology is of great interest. In the process, monolithic integration of a complementary inverter using one 2D active film is a milestone. MoS₂ is one of the best choices for active layers for the high-performance and large-scale 2D transistor integration. However, due to the defects and impurities in the transistor structure, fabricating high-performance complementary MoS₂ FETs, particularly the p-channel FET, is challenging and causes difficulties for integrating complementary MoS₂ circuits. This work found that the defects in MoS₂ transistors form a similar low electron barrier to metal contacts with different work functions. Although the defects promote electron injection, they hinder hole injection and lead to low current drive of MoS₂ p-FET. A clean contact interface is essential to improve hole injection into the MoS₂ p-channel. To this end, this work used a slow electron-beam evaporation method to form the transistor contacts. The MoS₂ p-FETs with Pt contacts formed by this method show improved output current. Furthermore, by using RF O₂ plasma to passivate the surface of the MoS₂ active layer, the MoS₂ p-FETs show a higher current drive, which is comparable to the high-current MoS₂ n-FET. High-gain MoS₂ inverters have been integrated on a single substrate using the complementary MoS₂ FETs. To further improve the transistor characteristics and reduce the inverter power consumption, this work fabricated a complementary MoS₂ inverter with the 2D h-BN gate dielectric. By developing a single-atomic layer etching method to control the thickness of the h-BN film, the h-BN gate dielectric is scaled down to a thickness of a few atomic layers while maintaining the dielectric quality.

Date of Award	2020
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology