Influence of vacancy on spontaneous polarization of wurtzite AlN： a maximally localized Wannierfunction study

Abstract

By using first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory, the maximally localized Wannier functions of N vacancy and Al vacancy with different charge states in wurtzite AlN are calculated. With the shape and center of the computed Wannier function, the electronic structure and the spontaneous polarization of vacancy are studied respectively. The results show that N–Al bond possesses a large ionicity. It is found that the electrons of the dangling bonds displace to the positions of vacancies in N vacancy structure, while in Al vacancy structure the electrons of dangling bonds keep away from vacancies and move to the other side of N atoms. Since the vacancy breaks the centrosymmetry of the [1010] and [1210] orientations, the polarization will be induced in these two directions, and the polarization will increase as the charge increases. In the [0001] orientation, the spontaneous polarization in N vacancy will reverse as charge increases because of the dramatic variation of the electronic structure. Contrary to N vacancy, the reversion does not occur although the spontaneous polarization of Al vacancy increases as charge increases.

The Effect of Defect Charge and Parasitic Surface Conductance on Aluminum Nitride RF Filter Circuit Loss

“…With the development of semiconductor technology, the excellent radio frequency (RF) characteristic of high-resistance silicon (HR-Si) is gradually discovered. It is shown that AlN films deposited directly on HR-Si have large RF losses, which is due to the large lattice mismatch and thermal mismatch between AlN and HR-Si, as well as the introduction of unintentional doping during the growth process [ 4 , 5 ]. It results in a large number of point defects in AlN materials, including Al vacancies and N vacancies which will form impurity scattering centers in the material and reduce carrier mobility and device performance while reducing its service life [ 6 , 7 , 8 ].…”