Optical and structural evidence of the grain-boundary influence on the disorder of polycrystalline CdTe films

We report the linear behavior of the band-tail parameter as a function of the reciprocal of the grain size in polycrystalline CdTe. On the other hand, the study of the full width at half maximum of the x-ray diffraction peak shows a similar behavior, which indicates that the disorder increases as grain size diminishes. A theoretical analysis justifies that the behavior is ruled by the contribution of the grain-boundary traps, and the trap concentration is calculated. Both results constitute experimental evidences of the grain-boundary disorder, which was quantified, and demonstrate that it is caused by the extension of the grain- boundary effect into the grain. (C) 1999 American Institute of Physics. [S0003-6951(99)04420-4].