PHOTOCONDUCTIVITY AND THERMOELECTRIC-POWER OF ZNXCD1-XSE FILMS

Zn, Cd1-xSe(0 less than or equal to x less than or equal to 1) films w ere deposited by two zone hot wall evaporation technique. X-ray diff r action analysis of the films indicated a predominant wurtzite structur e for x<0.5, which changed to zinc blende structure for x>0.7. The fil ms had a mixed structure for 0.5<x<0.7. The films were highly resistiv e (resistivity varying within 3 Omega cm to 1.5 x 10(5) Omega . cm for 0 less than or equal to x less than or equal to 1.0) with partially d epleted grains. The optical band gap (E(g)), determined from the refle ctance measurements, indicated a direct transition with a bowing effec t in E(g) versus x plot. The conductivity at low temperature (for x<0. 6) could be explained by thermionic emission over the intercrystalline barrier, while for higher a quantum mechanical tunneling through the barrier became predominant. The variation of the barrier height (E(bd) ) With the intensity of illumination was obtained from the photoconduc tivity measurements. The majority carrier capture cross-section (1-4x1 0(-18) cm(2)) of the grain boundary traps (1x10(11)-1x10(12) cm(-2)) w as determined. The effect of the intercrystalline barrier on the therm oelectric power measurements was also considered.