Computational design of a polymorph for 2D III-V orthorhombic monolayers by first principles calculations: excellent anisotropic, electronic and optical properties

Using first principles calculations, we have designed a new polymorph for two-dimensional (2D) III-V group materials with an orthorhombic phase, including BN, BP, BAs, AlN, AlP, and GaN, and investigated their structural, electronic, and optical properties. The phonon dispersion calculations have shown that BN, BP, AlN, and GaN possess excellent dynamic stabilities. The 2D BN is a direct semiconductor, and its bandgap predicted by PBE and HSE calculations is 0.76 and 1.73 eV, respectively. The calculated mobilities of the BN, AlN, and GaN monolayers have shown their high conductivities, and the monolayered AlN and GaN possess strong anisotropic carrier transport characters. The 2D AlN and AlP and GaN monolayers are found to be indirect semiconductors with bandgaps in the range of 0.66-1.65 eV. The 2D BN and BP monolayers exhibit extremely high and anisotropic absorbance, and their absorption energy range covers the whole solar spectrum, rendering them potential candidates for applications in solar cells. More importantly, their optical properties are shown to have highly anisotropic optical absorbance, making them promising candidates for manufacturing anisotropic optoelectronic devices. Our computational study not only provides a new class of 2D materials to enrich the material genome database, but also paves the way for practical applications of 2D III-V materials for electronic and optoelectronic devices.