Electronic properties and photon scattering of buckled and planar few-layer 2D GaN

The electronic structure, charge transfer, and photon scattering of the buckled and planar few-layer two-dimensional (2D) GaN are investigated based on the first-principles calculations. The calculated results show that the H passivated monolayer, bilayer, and trilayer buckled GaN are with direct band gap (4.51 eV, 2.47 eV, and 1.92 eV) which decrease as the number of atomic layers increases. The monolayer, bilayer, and trilayer planar GaN are with indirect band gap (3.41 eV, 3.36 eV, and 3.18 eV) which limited change as the number of atomic layers increases. The charge transfer occurs between the atoms in adjacent layers due to polarization in the three buckled structures, and the charge transfer occurs between the atoms within the layers since there is no polarization in the three planar structures. The lattice vibration modes are affected by the symmetry and the interaction between the atomic layers. The peak positions in the Raman spectra of the buckled GaN and the corresponding planar GaN are different. The peak positions in the Raman spectra corresponding to the lattice vibration modes of the buckled GaN and the planar GaN are redshifted or blueshifted with the number of the atomic layers.