Lattice deformation and phase transition of aluminum nitride studied by density functional theory calculations

Abstract

The density functional theory (DFT) was employed to understand the ferroelectric behaviors of wurtzite (WZ)-type aluminum nitride (AlN). To explain the decrease in the coercive field (E_c) due to lattice deformation, the total energy and enthalpy of the strained WZ phase were compared to those of the non-polar (NP) phase, which acted as a transition state during polarity switching. The shrinkage of the c-axis length and elongation of the a-axis length were favorable for reducing E_c. In addition, the calculated residual stress in the transient NP phase was as high as 30 GPa, suggesting that such a high residual stress may be related to the polarity switching behavior under a very high electric field.