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 Zn xCd1-xSe films showed a bowing effect, with a bowing parameter of abou t 1.26. Microstructural information was obtained from X-ray diffractio n and transmission electron microscopy (TEM) measurements, which indic ated a predominant wurtzite structure for x < 0.5 and a zinc blende st ructure for x > 0.7. The grain size, determined from scanning electron microscopy and TEM, was observed to decrease with increasing zinc con tent in the films. The films were highly resistive and polycrystalline in nature, with partially depleted grains. An optical method, develop ed on the basis of the model of Dow and Redfield, was used to determin e the barrier height and the density of trap states at the grain bound ary region, along with the carrier concentration of the polycrystallin e films. The variation of the electric field within the grains also wa s studied. The effective mass of the carriers varied with x and indica ted a bowing effect.