Hydrogenation-induced interfacial bonding effects on the structural, electronic, and optical properties of GaN bilayer

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Employing first-principles calculations, effects of hydrogenation on the structural, electronic, and optical properties of AB-stacked GaN bilayer are explored systematically. Hydrogenation can transform the planar GaN bilayer into novel diamane-like monolayer by inducing the interfacial atom bonding. Hydrogenation not only can enhance the dynamical stability of GaN bilayer, but also cause its electronic characteristics to be changed from an indirect to direct gap. In addition, the band structure and optical absorption of hydrogenated GaN bilayer are strongly dependent on the interfacial atom bonding. In particular, hydrogenated GaN bilayer with the interfacial Ga–N bonding has strong absorbance coefficients for the visible part of the sunlight (beyond 105 cm−1). More interestingly, the observed binding energy of first bright bound exciton can attain 1 eV in the interfacial Ga–N bonding, which can slow down the recombination of photogenerated electron-hole pairs. These results enrich the deep understanding of the properties of novel hydrogenated GaN bilayer.