Zinc band bending

The bulk crystal structure of zinc-blende-type III-V semiconductors is cubic, that is, of point group symmetry (Section 13.2). Such crystals are optically isotropic in first-order approximation, that is, if symmetry reducing effects, such as finite k-vector electric fields and other effects are neglected [138]. Then the RAS signal should originate from the surface that is anisotropic due to the termination of crystal periodicity and due to the surface reconstraction [127-129]. Apart from the structural anisotropy and related effects such as strain, the surface electric field accompanied by the band bending will modify electronic eigenstates and induce an optical anisotropy as well. 

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