Monolayer Bi2O2Se is a promising post-silicon-era semiconductor candidate because of its simultaneous excellent device performance and high ambient stability.
high carrier mobility, and good air stability, it has the possibility to serve as the channel material of postsilicon era. Disappointingly, most existing 2D semiconductors cannot meet these requirements simultaneously, including the most concerned 2D MoS 2 and black phosphorene (BP). [8][9][10][11][12] Experimentally, 2D MoS 2 FETs have been scaled down to the sub-10 nm region, [13][14][15] but the low on-current (<250 µA µm −1 ) mainly caused by the low carrier mobility fails to meet the International Technology Roadmap for Semiconductors (ITRS) requirements, [16] which is in accord with the results of the ab initio quantum transport simulations. [17] 2D BP FETs own high carrier mobility but are so sensitive to the air that their device performance degenerates when exposed under ambient condition. [18,19] Therefore, it is crucial to find a 2D channel material with a modest band gap, large drive current, and high air stability to continue Moore's law.Tellurium (Te), a p-type semiconductor, consists of individual helical Te chains that are stacked together by van der Waals force. [20] Recently, atomically thin tellurene (2D form of Tellurium) has been fabricated by a substrate-free solution process and molecular beam epitaxy on a graphene/6H-SiC substrate, respectively. [21][22][23] 2D tellurene possesses an anisotropic structure and is constituted of alternate tetragonal and hexagonal rings. [24,25] The band gap of tellurene monotonically decreasesThe merging 2D semiconductor tellurene (2D Group-VI tellurium) is a possible channel candidate for post-silicon field-effect transistor (FETs) due to its high carrier mobility, high drive current, and excellent air stability. The performance limits of sub-5-nm ML tellurene metal-oxide-semiconductor FETs (MOSFETs) are explored by employing exact ab initio quantum transport simulations. An optimized p-type ML tellurene MOSFET meets both the high performance (along both the armchair and the zigzag directions) and the low power (along the armchair direction) requirements of the International Technology Roadmap for Semiconductors (ITRS) at a gate length of 4 nm with a negative capacity dielectric. Hence, choosing ML tellurene as the channel material provides a novel route to continue the Moore's law to 4 nm.
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.
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