Electrical properties of Er-doped CdS thin films

Cadmium sulfide thin films were prepared by chemical bath on glass substrates at 80 degrees C. CdS was Er-doped during the growth process by adding water-diluted Er(NO3)(3)3 center dot H2O to the CdS aqueous growing solution. The relative volume of the doping solution was varied in order to obtain different doping levels. The crystalline structure of CdS:Er films was cubic zinc blende for all the doped layers prepared. The (111) interplanar distance has an irregular variation with the Er doping level. Consequently, the band gap energy (E-g) firstly increases and afterward diminishes becoming, at last, approximately constant at around E-g=2.37 eV. For higher doping levels, in the as-grown films, dark electrical conductivity (sigma) values reach 1.8x10(-2) Omega(-1) cm(-1) at room temperature. The logarithm of sigma vs 1/kT plot, where k is Boltzmann's constant and T the absolute temperature, indicates an effective doping of CdS as a result of the Er introduction into the lattice of the material. Hall effect measurements reveal a n-type doping with 2.8x10(19) cm(-3) as maximum carrier density. (c) 2007 American Institute of Physics.