OPTICAL-PROPERTIES OF ZNXCD1-X SE FILMS

ZnxCd1-xSe films (0 < 1.0) were deposited by the hot wall evaporation technique onto glass substrates. The optical band gap (E(g)) in the ZnxCd1-xSe films showed a bowing effect, with a bowing parameter of about 1.26. Microstructural information was obtained from X-ray diffraction and transmission electron microscopy (TEM) measurements, which indicated a predominant wurtzite structure for x < 0.5 and a zinc blende structure for x > 0.7. The grain size, determined from scanning electron microscopy and TEM, was observed to decrease with increasing zinc content in the films. The films were highly resistive and polycrystalline in nature, with partially depleted grains. An optical method, developed on the basis of the model of Dow and Redfield, was used to determine the barrier height and the density of trap states at the grain boundary region, along with the carrier concentration of the polycrystalline films. The variation of the electric field within the grains also was studied. The effective mass of the carriers varied with x and indicated a bowing effect.