CuIn1-xGaxS2 wide gap absorbers grown by close-spaced vapor transport

CuIn1-xGaxS2 wide gap absorber thin films were grown by means of a low cost method using the close-spaced vapor transport principle. No high-cost vacuum apparatus is needed. From X-ray analyses, the chalcopyrite superstructure was found to be present on all the samples, except when the substrate temperatures were below 300 degreesC. Energy dispersive spectroscopy studies showed a large quasi-stoichiometry range, corresponding to substrate temperatures between 300 and 600 degreesC (glass substrate use limit). For initial pressures in the reactor close or equal to the atmospheric value, quasi-columnar structures were grown, with crystallite sizes of about 1 mum and thicknesses of the order of 2 mum. The deposition rates were about 0.05 mum/min. For low pressures (< 0.1 bar), the deposition rates are high (up to 0.5 mum/ minute) and the crystallite sizes can be of several micrometers. The optical absorption showed energy gap values up to 1.65eV and rather sharp absorption fronts. The thin film resistivities are between 30 and 5000 Omega cm, depending on the experimental growth conditions. (C) 2004 Elsevier B.V. All rights reserved.