Electronic and Optical Properties of Novel Janus Monolayer X₂AsP (X = B, Al, Ga)

Two-dimensional (2D) materials offer an optimal basis to realize intriguing quantum phenomenon and develop versatile nanoscale devices. The recent successful synthesis of 2D double-layer honeycomb (DLHC) AlSb revealed that it possesses interesting semiconducting properties, which inspires further investigation into robust DLHC materials. In this theoretical study, we theoretically predict novel Janus DLHC materials X<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>AsP (X = B, Al, Ga), from which Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>AsP and Ga<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>AsP are found to possess dynamic and mechanical stability, confirmed through first-principles calculations. Among the two stable materials, Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>AsP has an indirect bandgap of 1.964 eV, whereas Ga<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>AsP has a direct bandgap of 0.378 eV. Both of these monolayers are found to have low values of carrier effective masses, implying their potential for application in high-speed nanoelectronic devices. In addition to the electronic properties, the optical properties of X<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>AsP are calculated. Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>AsP possesses a high absorption co-efficient of 14.1×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and a narrow linewidth of 1.68 eV for out-of-plane polarization of incident light, indicating that the material may find application as a selective UV detector. Besides, for in-plane polarization, a moderate linewidth (3.55 eV) and a high value of peak reflectance of 48.45% are obtained for Ga<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>AsP, implying its potential usage in mid-UV and far-UV region. Our findings, such as, direct bandgap, low effective mass and desirable optical properties highlight the potential application of novel Janus 2D monolayer, X<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>AsP in high-performance, and efficient electronic and optoelectronic devices.