DFT investigation of geometrical, vibrational, elastic, electronic, optical, and thermoelectric properties of aluminum pnictogens compounds

The aim of this study is to investigate the geometrical, vibrational, elastic, electronic, optical, and thermoelectric characteristics of aluminum pnictides in monolayer square lattice and bilayer hexagonal phases (s- and h-AlX; X = N, P, As) using first principles. The s- and h-AlX materials are mechanically, energetically, and dynamically stable, through phonon dispersion and elastic properties investigations. It was observed that s-AlX materials exhibited both direct and indirect bandgaps, whereas h-AlX materials exhibited indirect bandgap behavior. The energy bandgap values for s- and h-AlX materials measured between 0.79 eV and 3.49 eV for the PBE functional, and between 1.49 eV and 4.74 eV for the HSE06 functional. The effective mass, mobility and relaxation time of electron carriers as well as hole carriers from the band structure of s- and h-AlX are examined to gain a better perception into these materials. The AlP monolayer square lattice phase has the highest mobility and relaxation time of 266129.60 cm²V⁻¹s⁻¹ and 740369.83 fs among entire s- and h-AlX materials. The optical characteristics of s- and h-AlX materials are examined in the existence of field polarizations. The thermoelectric properties of the AlX materials are assessed for temperature dependent. Our investigated results expose that AlP/AlP and AlAs/AlAs are the proficient thermoelectric materials at room temperature in the considered sequence. The present investigation shows that the s- and h-AlX materials are mostly active in the UV region of electromagnetic spectrum, and may find applications in UV-photodetectors and UV-protectant materials.