Electric-Field Control in Phosphorene-Based Heterostructures

Abstract

Phosphorene is a graphene-like material with an intermediate band gap, in contrast to zero-gap graphene and large-gap dichalcogenides or hexagonal boron nitride (hBN), which makes it more suitable for nanoelectronic devices. However, inducing band-gap modulation in freestanding phosphorene nanoribbons (PNRs) is problematic, as high in-plane electric fields are necessary to close the gap. We perform here a detailed investigation concerning the substrate influence on the electric-field control exerted by an external gate, using the density functional theory–non-equilibrium Green’s functions (DFT-NEGF) framework. It is established that the interaction with a hexagonal boron nitride supporting layer significantly enhances the gap modulation. Furthermore, we address the issue of contacting the PNRs, by using conducting graphene nanoribbons embedded in the support hBN layer. Within this setup, a measurable spin polarization is achieved owing to the anti-ferromagnetic coupling between the edges of the graphene nanoribbons.

Gap engineering effects on transport and tunneling magnetoresistance properties in phosphorene ferromagnetic/normal/ferromagnetic junction

“…The reduction in gap width contributes to the disappearance of evanescent transmission modes (illustrated in blue regions) and an amplification of propagating transmission modes (highlighted in red regions). This behavior finds explanation in the dispersion relation described by equation (9). As a result, it can be affirmed that the gapless structure of GFPJ tends to significantly improve transmission compared to a gapped structure, which in turn can enhance the conductance in both ferromagnetic configurations.…”

“…The system comprises two barriers (well) with width d b (d w ) are connected to two semi-infinities monolayer phosphorene region in x direction, as illustrated in figure 1(a). It is worth emphasizing that the band gap (E g ) of the monolayer phosphorene in the device can be tuned through the controlled application of an electric field [6,7,9,20,21,27,29]. In simpler terms, applying the electric field can reduce and eventually close the band gap.…”

“…In a similar context, it is found that the reduction in band gap energy under pressure of bilayer phosphorene nanoribbons generates an increase in current and transmission probability near the conduction band [16]. Pantis-Simut et al [9] have established that the reduction of the band gap by an applied in-plane electric field produces an improvement in conductance for phosphorene-based heterostructures. Guo et al [19] have reported the opening of band gap by tensile strain of black phosphorene (BP) at zero temperature, resulting in a significant reduction in hole mobility and a weak enhancement in electron mobility.…”

“…However, modulating the gap is crucial to control the transport and optical properties in 2D materials, enabling its potential use in the semiconductor industry. There are various strategies to control the gap in 2D materials, such as applying electric [6][7][8][9][10][11][12][13], magnetic fields [14], or strain [15][16][17][18][19], presence of impurities [20], or perforation of nanoribbons (antidots) [21], as well as changing of layers number [13,22] or deposition and encapsulation on/in multilayers [23] or forming nanoribbons [15] or multilayer structures [13]. Additionally, it can be achieved through oxidation [24,25], passivation [26], or a combination of diverse effects, such as the interaction between electric fields and strain [27][28][29], or between electric fields and doping [20].…”

“…In relation to transport in a modulated gap in phosphorene, several reports have addressed the impact of the engineering gap on transport properties [9,14,16,19]. For instance, it has reported the reduction of band gap by an applied magnetic field in a doped PN device based in phosphorene, minimizing electronic resistivity and boosting the current passing through the device [14].…”