We present the results obtained by photomodulation (PM) at room temperature of semiconductor US thin films grown in large area (450 cm(2)). The thin films were deposited on conducting glass (SnO2:F 7 Omega/rectangle) by radio frequency-planar magnetron sputtering with a substrate temperature (T-s) of 250 degreesC, an Argon pressure of 20 mTorr, a radio frequency power of 300 W and with a deposition time (t(d)) of 60 min. A thermal treatment with CdCl2 in these thin films at different annealing times was carried out. In general the PM spectra show a better crystal quality in the US thin films annealed with CdCl2 which is corroborated with atomic force microscopy (AFM) and observed in the efficiency of the solar cells processed with these films. (C) 2003 Elsevier B.V. All rights reserved.