Tuning the thermoelectric Power Factor and exciton binding energy of monolayer group-III nitrides through alloying

Two-dimensional (2D) group-III nitride semiconductors (h-BN, h-AlN, h-GaN, and h-InN) have attracted attention due to their desirable electronic, optical, and thermoelectric properties. We performed density functional theory (DFT) calculations to investigate 2D B_1-xAl_xN, Al_1-xGa_xN, and Ga_1-xIn_xN structures and assess how alloying impacts the material properties. In addition, we calculated the thermoelectric properties of these structures using Boltzmann transport theory based on DFT and the optical properties using the GW method and the Bethe–Salpeter equation. We find that by changing the alloying concentration, the band gap and exciton binding energies of each structure can be tuned accordingly, and for certain concentrations, a high thermoelectric performance is reported. In addition to confirming the dynamical stability of these alloys through phonon calculations, we treated the electron relaxation time rigorously using Deformation Potential Theory (DPT) and obtained an accurate estimate for the thermoelectric power factor. With the ability to engineer these properties by alloying 2D group-III nitrides, we believe that this work will play an important role for experimentalists focusing on next-generation electronic, optoelectronic, and thermoelectric devices.