Thermal conductivity at finite temperature and electronic structure of the ultra-wide band gap fluorinated 2D GaN

Passivation makes 2D hexagonal structure more stable than the planar variant. Surface fluorinated monolayer of GaN have been found to have ultra-wide band gap and have promising applications in optoelectronic conversion devices. In this work, using theoretical method, we have explored the thermal conductivity as well as the electronic structure of F-GaN. It has a low thermal conductivity of 7.67 W (mK)-1 due to the low group velocity and short phonon lifetime. The calculated direct band gap value is 4.63 eV, which could be modulated by strain and biaxial strain is found to more effective. Attractively, direct band gap can be maintained under tensile strain. Breakdown of symmetry by uniaxial strain lifts the band degeneracy of the VBM, which will lead to polarized light emission. The in-depth analysis shows that Ga-F as well as N-F bonds are strongly ionic, which is responsible for its low thermal conductivity and ultra-wide band gap.