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
fluorinated GaN. It has a low thermal conductivity of 7.67 W/(mK) 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.