Analysis of Broken Symmetry in Convergent-Beam Electron Diffraction along ⟨11(2)over-bar0⟩ and ⟨1(1)over-bar00⟩ Zone-Axes of AlN for Polarity Determination

To accurately and easily determine the polarity of AlN using transmission electron microscopy, we compare the convergent-beam electron diffraction (CBED) patterns along the widely used < 11 (2) over bar0 > and < 1 (1) over bar 00 > zone-axes. For the < 11 (2) over bar0 > zone-axis, the diffraction disk of g = 0002 differs from that of g = 000 (2) over bar, while for < 1 (1) over bar 00 > the diffraction disks of g = 0002 and 000 (2) over bar are similar. The preferential clarity of these two disks is explained using Bloch-wave dynamical theory. To further support the explanation, we compare the results of GaN case. On the basis of our analysis, we conclude that the CBED patterns of the (11 (2) over bar0) zone-axis are more useful for accurately determining AlN polarity compared to the CBED patterns along the (1 (1) over bar 00) zone-axis. (C) 2013 The Japan Society of Applied Physics