Alternative procedure for the fabrication of close-spaced sublimated CdTe solar cells CdTe thin films deposited by close space vapor transport ͑CSVT͒ under variable growth conditions and postthermal and chemical treatments were studied by means of photoconductivity measurements in the temperature range of 90-300 K. The influences of the deposition temperature gradient, the oxygen content in the growth chamber, and the CdCl 2 treatment and chemical etching upon the intergrain barrier height of CSVT polycrystalline CdTe thin films were determined. The grain boundary barrier height (E b ) as a function of the intensity of the incident light was analyzed, and values of E b under illumination of 100 mW/cm 2 ͑AM1͒ were obtained in each case. These results are important for improving CdS/CdTe solar cell performance in the near future.
Photoluminescence (PL) studies in GaN thin films grown by infrared close space vapor transport (CSVT-IR) in vacuum are presented in this work. The growth of GaN thin films was done on a variety of substrates like silicon, sapphire and fused silica. Room temperature PL spectra of all the GaN films show near band-edge emission (NBE) and a broad blue and green luminescence (BL, GL), which can be seen with the naked eye in a bright room. The sample grown by infrared CSVT on the silicon substrate shows several emission peaks from 2.4 to 3.22 eV with a pronounced red shift with respect to the band gap energy. The sample grown on sapphire shows strong and broad ultraviolet emission peaks (UVL) centered at 3.19 eV and it exhibits a red shift of NBE. The PL spectrum of GaN films deposited on fused silica exhibited a unique and strong blue-green emission peak centered at 2.38 eV. The presence of yellow and green luminescence in all samples is related to native defects in the structure such as dislocations in GaN and/or the presence of amorphous phases. We analyze the material quality that can be obtained by CSVT-IR in vacuum, which is a high yield technique with simple equipment set-up, in terms of the PL results obtained in each case.
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