In zincblende semiconductors, the non-polar (110) surface was more stable than all polar surfaces because the formation of the latter requires the creation of charge-neutralizing but energetically costly surface reconstruction. First-principles calculations of CuInSe2 revealed this in the double-zincblende (chalcopyrite) structure, the defect-induced reconstructions make the (112)-cation plus (¯1¯1¯2)-anion polar facets lower in energy than the non-polar (110) plane, despite the resulting increased surface area. It was shown that this spontaneous faceting resulted from the remarkable stability of surface defects (Cu vacancy, Cu-on-In antisite) in chalcopyrites, and explained the hitherto puzzling formation of polar micro-facets when one attempts to grow epitaxially a non-polar chalcopyrite surface.

Defect-Induced Nonpolar-to-Polar Transition at the Surface of Chalcopyrite Semiconductors. J.E.Jaffe, A.Zunger: Physical Review B, 2001, 64[24], 241304 (4pp)