Exploring original properties of GaN-BN alloys using high-throughput ab initio computation

• Published in: Optik (Stuttgart) 2022-07, Vol.261, p.169166, Article 169166
• Main Authors: Maiz Hadj Ahmed, H., Benaissa, H., Zaoui, A., Ferhat, M.
• Format: Article
• Language: English
• Subjects: Band-gap; Bowing parameter; DFT; Engineering Sciences; GaN-BN alloys; High-throughput computations
• ISSN: 0030-4026; 1618-1336
• DOI: 10.1016/j.ijleo.2022.169166

GaN alloyed with boron (B) is a potential candidate for wide band gap materials and for ultraviolet optoelectronic device applications. Using evolutionary algorithm and density functional theory, we investigate here the thermodynamic, mechanical, dynamical and optical properties of GaN-BN alloys. Three ordered BxGa1-xN structures: cubic (BGa3N4, and B3GaN4, space group P-43 m), and tetragonal (BGaN2, space group P-42 m) have been explored. The calculated relatively large mixing enthalpies point out that large miscibility gap exists in BGaN system (i.e., ΔH∼80 meV for x = 0.5). However, weak ΔH for x = 0.25 (ΔH∼24 meV) suggests that BGa3N4 compound is –thermodynamically- slightly unstable. Analysis of the computed elastic constants and phonon dispersion curves reveal that the three ordered structures are mechanically and dynamically stable. Our results show that BGa3N4 exhibits outstanding mechanical properties, such as a large bulk modulus (~328 GPa), important shear modulus (~248 GPa), and strong Vickers hardness of ~ 33 GPa. Moreover, the use of LDA-1/2 functional evidences that the incorporation of boron in GaN gives a huge optical band-gap bowing parameter of b∼11 eV for the entire range of composition, which is in agreement with experiment. In addition, we highlight the prevailing role of chemical and stress effects responsible of the giant disorder in this ternary system.