State Key Laboratory of Information Photonics and Optical Communications and School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, P. R. China.
Nanoscale. 2017 Sep 28;9(37):14047-14057. doi: 10.1039/c7nr03941g.
Contact engineering is a possible solution to decrease the pervasive Schottky barrier in a two dimensional (2D) material transistor with bulk metal electrodes. In this paper, two kinds of typical van der Waals (vdW)-type electrical contacts (a 2D metal contact and a 2D material/bulk metal hybrid contact) in monolayer (ML) black phosphorus (BP) transistors are investigated by ab initio energy band calculations and quantum transport simulations. Compared with the traditional bulk metal Ni contact, the gate electrostatic control is significantly improved by using both 2D graphene and borophene electrodes featuring a decrease of 30-50% in the subthreshold swing and an increase by a factor of 4-7 in the on-state current due to the depressed metal induced gap states and reduced screening of the 2D metal electrodes to the gate. In contrast, graphene insertion between the Ni electrode and ML BP shows only a slight improvement in the gate electrostatic control ability and BN insertion shows almost no improvement. The higher efficiency using the 2D metal contact than the 2D material/bulk metal hybrid contact in improving the ML BP FET device performance also provides helpful guidance in the selection of vdW-type electrical contacts of other 2D transistors.
接触工程是降低二维（2D）材料晶体管中体金属电极普遍存在的肖特基势垒的一种可行方法。在本文中，通过从头算能带计算和量子输运模拟研究了两种典型的范德华（vdW）型电接触（二维金属接触和二维材料/体金属混合接触）在单层（ML）黑磷（BP）晶体管中的应用。与传统的体金属 Ni 接触相比，使用二维石墨烯和硼烯电极可显著改善栅极静电控制，亚阈值摆幅降低 30-50%，导通电流增加 4-7 倍，这是由于金属诱导的能隙态降低和二维金属电极对栅极的屏蔽作用减弱。相比之下，Ni 电极和 ML BP 之间插入石墨烯只会略微改善栅极静电控制能力，而 BN 插入几乎没有改善。在改善 ML BP FET 器件性能方面，二维金属接触比二维材料/体金属混合接触的效率更高，这也为选择其他二维晶体管的范德华型电接触提供了有益的指导。
