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Why GaN has internal polarization? I know that in wurtzite crystal structure, the atomistic bonds are not equivalent and as a result there appears a net dipole and consequently a polarization. But what is special about the Nitrides like InN and GaN which atoms prefer to arrange in some way that the bonds are not symmetric?

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  • $\begingroup$ The nitrides are not that special, just special relative to, say, GaAs. Googling 'gallium nitride polarization' leads to many papers and lecture notes that touch on this. Basically, the wurtzite structure is stretched on the c axis in the III-nitrides, breaking symmetry and causing the net polarization. $\endgroup$
    – Jon Custer
    Oct 18, 2014 at 16:29
  • $\begingroup$ Yes, my question is why it is streched along c-axis $\endgroup$
    – Roy
    Oct 18, 2014 at 19:03

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It's because there are alternating layers of + and - ions in the c-direction, yielding a dipole in the crystal. See Tasker -- http://www.surface.tulane.edu/teaching/classnotessurface/TaskerJPhysC79.pdf

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    $\begingroup$ Welcome to Physics! Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. $\endgroup$
    – Kyle Kanos
    Dec 2, 2014 at 1:48
  • $\begingroup$ Well, it is technically an answer I think, because of the first sentence. But certainly it would be improved by adding more details. $\endgroup$
    – David Z
    Dec 2, 2014 at 5:27

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