Synthesis and growth of large stoichiometric single crystals of copper indium diselenide by horizontal varying gradient zone freeze technique

A new method to grow large single crystals with stoichiometry close to 1:1.2 of CuInSe2, an important member of the I-III-VI2 family of chalcopyrite semiconductors for optoelectronic device applications, is described. This is called the horizontal varying gradient zone freeze technique and consists of the selenization in the liquid phase of stoichiometric Cu and In and later solidification under programmed varying gradient in a fully automated multiple zone horizontal furnace. All ingots obtained with Se pressure between 15 and 1760 mm of Hg were single phase having chalcopyrite structure and p-type conductivity. X-ray, DTA, optical and electrical characterizations of the samples taken from different parts of the ingots were made. From energy dispersive spectroscopy it is found that the samples of the ingot obtained with Se pressure at 836 mm of Hg were much closer to the ideal stoichiometry 1:1:2.