Experimental two-dimensional (2D) black phosphorus (BP) transistors typically appear in the form of Schottky barrier field effect transistors (SBFETs), but their performance limit remains open. We investigate the performance limit of monolayer BP SBFETs in the sub-10 nm scale by using ab initio quantum transport simulations. The devices with 2D graphene electrodes are apparently superior to those with bulk Ti electrodes due to their smaller and tunable Schottky barrier heights and the absence of metal induced gap states in the channels. With graphene electrodes, the performance limit of the sub-10 nm monolayer BP SBFETs outperforms the monolayer MoS, carbon nanotube, and advanced silicon transistors and even can meet the requirements of both high performance and low power logic applications of the next decade in the latest International Technology Roadmap for Semiconductors. It appears that the ML BP SBFETs have the best intrinsic device performance among the reported sub-10 nm 2D material SBFETs.

The interfacial properties of β phase borophene contacts with other common two-dimensional materials (transition-metal dichalcogenides, group IV-enes and group V-enes) have been systematically studied using a density functional theory (DFT) method. The zero tunneling barrier is found for all of the investigated β phase borophene contacts except for the case of β borophene/graphene. The chemically reactive properties and high work function (4.9 eV) of the stable β borophene lead to the formation of Ohmic contacts with silicene, germanene, stanene, black phosphorene, arsenene and antimonene. The advantage of the zero tunnel barrier remains when changing the borophene from the β phase to the Δ phase. Therefore, a high carrier injection rate is expected in these borophene contacts. Our study provides guidance on borophene for future two dimensional materials based device designs.

Tunneling field effect transistors (TFETs) based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low power devices. Here, we investigate the TFETs based on two different integration types: in-plane and vertical heterostructures composed of two kinds of layered phosphorous (β -P and δ -P) by ab initio quantum transport simulations. NDR effects have been observed in both in-plane and vertical heterostructures, and the effects become significant with the highest peak-to-valley ratio (PVR) when the intrinsic region length is near zero. Compared with the in-plane TFET based on β -P and δ -P, better performance with a higher on/off current ratio of ∼ 10 6 and a steeper subthreshold swing (SS) of ∼ 23 mV/dec is achieved in the vertical TFET. Such differences in the NDR effects, on/off current ratio and SS are attributed to the distinct interaction nature of the β -P and δ -P layers in the in-plane and vertical heterostructures.

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Two-dimensional (2D) layered phosphorus possesses multiple structural phases with different properties. By using ab initio approaches, the electronic properties of vertical heterostructured compounds of different structural phases of layered phosphorus have been studied. Both type-I (symmetric) and type-II (staggered) band alignments have been realized in the van der Waals heterostructures. Through appropriate doping, the type-II band alignment can be further tuned to type-III (broken). The multiple types of band alignment suggest great potential of phase manipulated 2D phosphorus for next-generation novel electronics.