Shallow electronic states induced by prismatic stacking faults in AlN and GaN
Wurtzite materials such as AlN and GaN can exhibit prismatic stacking faults on the (1-210) plane with a stacking fault displacement vector RD = ½[10-11]. These faults thread in the  direction and may arise in growth on the (0001) plane from the merging of independently nucleated islands. Merging islands that have different stacking sequences in the  direction, for example ABAB… versus ACAC…, give rise to the faults. The formation energy of such a stacking fault in AlN has been determined using first-principles total energy calculations to be 79 meV/Å2. The perturbation caused by the highly strained four-fold ring structure at the boundary is sufficient to create shallow stacking fault states 0.1 eV above the valence band maximum and 0.1 eV below the conduction band minumum. These results are compared to those obtained for GaN.
Northrup, J. E. Shallow electronic states induced by prismatic stacking faults in AlN and GaN. Applied Physics Letters. 2005 February 14; 86 (7): 71901.