Electronic and optical properties of polycrystalline semiconducting films

Abstract

The microstructure of polycrystalline semiconducting films is strongly dependent on nucleation and growth processes and hence deposition parameters. In general, anisotropic growth in the form of columns separated by intergranular regions takes place in the film. The electronic structure of the intergranular regions depends on the type and concentration of traps, defects and impurities present. Besides the thickness dependence, grain boundary potential affects the concentration and/or mobility of the carriers involved in the transport processes. The optical absorption and the position and shape of the absorption edge of the semiconducting films are affected by the microstructure. Results on the electron transport and optical properties of some chalcogenide and oxide semiconducting films will be reviewed in the light of various grain boundary phenomena. The possibility of activation or passivation of the electronic activity of grain boundaries and their effects on the performance of such devices as thin film solar cells and varistors will be discussed.