Graphene is a two-dimensional material with excellent properties, including high carrier mobility, thermal conductance, and mechanical strength, making it an essential material for applications in different industries [2–6]. However, its flat honeycomb structure, with sp2 hybridization, makes it less reactive, reducing its possible applications in areas such as catalysis. Unlike graphene, silicene [7], and germanene [8] are more reactive due to their atomic buckling. They also lack an intrinsic bandgap, reducing their possible applications in electronic devices, such as field-effect transistors. This is one reason why the search for other 2D materials with new properties is constantly going on. Metals belonging to groups III and V are known to form low-dimensional systems on semiconductor surfaces [17–19]. Therefore, it is not surprising that these elements can also form stable 2D systems. In particular, there is interest in investigating phosphorene and arsenene, a couple of 2D group V materials. It has been possible to fabricate black phosphorene (puk-P), a monolayer of phosphorus, by exfoliating black phosphorus [20–22]. Its atomic structure is puckered, different from flat graphene, buckled silicene, and germanene. However, another possible phosphorene geometry, similar to that of silicene and germanene, is that of blue phosphorene (buk-P), which was stabilized on an Au (111) substrate [23]. On the other hand, the possible existence of a two-dimensional arsenic system has been investigated [24]. Two types of structures have been proposed, one buckled (buk-As) and the other puckered (puk-As), similar to blue and black phosphorene, respectively. In all cases, a band gap different from zero is predicted.
From their optical and optoelectronic properties, buckled and puckered phases of arsenene and phosphorene can be considered promising and outstanding candidates for several technological applications, such as nanophotonics. In the case of puk-P, it shows strong light–matter interactions in the mid-infrared (mid-IR), and visible frequency range because of its excellent carrier mobility, high values of nonlinear saturable absorption coefficients, strong PL emission in the infrared range, anisotropic optical properties, and high-tunable band-gap when stacked one on top of the other [17–19]. These properties allow a wide variety of applications ranging from mid-IR photonics to high-performance field effect devices, such as photodetectors, plasmonic devices with tunable resonance frequency, optical modulators, ultrafast pulse lasers, photodiodes, as well as optical signal processing devices [17, 20–23]. Several studies have revealed the stable existence of excitons and trions with high binding energies [19, 24, 25], making possible the applications in light-emitting and energy harvesting devices [26–28]. In the same way, puk-P is seen as a material with high photoelectrical conversion, making possible the construction of transistors [29, 30].
On the other hand, the fabrication of photodetectors with high responsivity in the near-infrared range has been achieved recently [31, 32], as well as phosphorene-based photodetectors integrated in waveguides [31]. Nonperturbative high harmonic generation properties have also been observed in puk-P, suggesting potential applications in extreme ultraviolet and attosecond nanophotonics [23]. Buk-P has been predicted to have high carrier mobilities, a wide absorption spectrum (from infrared to visible), and a strong absorbance in the ultraviolet region [33], allowing potential applications in electronic and photonic devices, as its band gap lies in the visible range. Its properties can be enhanced when forming vdW heterostructures with GaN, showing a high photocatalytic activity, and allowing applications in optoelectronics and solar energy conversion devices [34, 35]. On the other hand, the magnetic and optical properties of buk-P can be significantly improved if it is doped with Y, Nb, Mo, and Zr, since the absorption of infrared and visible light is enhanced in such systems [36]. These results suggest the potential applications of doped buk-P in optoelectronic and spintronic devices.
Furthermore, a semiconductor-metal hybrid nanostructure has been reported, consisting of a rectangular 2D array of buk-P inserted into an Au nanowire [33]. In this system, surface plasmon polaritons are observed, allowing the possibility of developing optical modulators, optical waveguides, photosensitive detectors, and nanoscale plasma devices [33]. Besides, high energy conversion efficiencies can be reached in other heterostructures based on buk-P, such as buk-P/MoS2 and buk-P/MoSe2, allowing potential applications in thin-film solar cells and light collectors [33, 37]. About buk-As, it has outstanding optical properties due to its stable buckled structure, suggesting its suitability for optoelectronic applications at room temperature [38]. It possesses a wide band gap, which is useful for fabricating transistors and high-efficiency optoelectronic devices [39]. The band gap can be tuned by molecular doping as well. By these mechanisms, the optical absorption of buk-As could be possible both in the visible and near-infrared ranges and more important, in the major range of the solar spectrum [39, 40]. The enhancement of the optical response makes possible the use of this material in optoelectronic and solar-energy harvesting devices [39, 40] for developing technologies based on renewable energy. Finally, concerning puk-As, it is a material with high carrier mobility and strong in-plane anisotropy [41]. Because of its outstanding optical properties, potential applications are light-emitting diodes, solar cells, and optoelectronic devices [42–45]. On the other hand, it has been proposed the fabrication of field-effect transistors (FET’s) based on puk-As [46] of high performance, high on/off ratio, high switching speed, and low energy dissipation. The optical properties of puk-As can also be enhanced when transition metals (TM) are adsorbed on it, as reported in Ref. [47]. The TM/arsenene systems can be used to design field emission and photocatalysis nanodevices [47] because the transition metals adsorbed in arsenene can cause an enhancement of the absorption spectrum in the visible and near-infrared regions, which leads to an improvement of the electronic and optical properties for application in visible light catalysis [47].
Although there are many investigations on phosphorene and arsenene, there is no complete comparative study of their structural, electronic, and optical properties. In this work, we present such comparative studies in their possible phases. In particular, we compare their electronic and optical properties using GW and the Bethe-Salpeter approaches, respectively. The study of these properties is very important due to the possible applications of these materials in the electronic and optoelectronic industries.
This paper is organized as follows: section 2 is devoted to a description of the computational details. In section 3, we present and discuss all the results of the structural, electronic, and optical properties. A summary of the results and conclusions is presented in section 4.