STRUCTURAL, ELECTRICAL AND OPTICAL-PROPERTIES OF CD-XZN1-XSE THIN-FILMS

X-ray diffraction and electron diffraction techniques indicate that Cd -x Zn1-xSe thin films on glass substrates have a polycrystalline natur e, with sphalerite structure for x less than or equal to 0.5 and wurtz ite structure for x greater than or equal to 0.6. The crystalline size in each composition increases with increasing the film thickness. The room temperature dark resistivity rho varies from one composition to another showing a transition at x = 0.55 The temperature dependence of rho of the deposited films revealed two conduction mechanisms, one be low 352 K due to shallow levels, surface states, and defects introduce d during the film growth, and over 352 K due to deep-level ionization following the ordinary semiconducting behaviour. The thermal activatio n energy of the free charge carriers decreases linearly with increasin g the molar fraction x of the CdSe content up to x = 0.55, above which it increases with increasing x. The optical constants of Cd-x Zn1-xSe thin films of different compositions were determined in the spectral range 400-2000 nm. The analysis of the absorption coefficient at and n ear the absorption edge indicates the existence of allowed direct tran sition energy gaps decreasing with increasing x.