ELECTRICAL-PROPERTIES OF CDTE-FILMS PREPARED BY CLOSE-SPACED SUBLIMATION WITH SCREEN-PRINTED SOURCE LAYERS

Abstract

CdTe films have been deposited by a close-spaced sublimation process with screen-printed CdTe layers as a new source. The source-layers were fabricated by screen printing and sintering slurries consisting of propylene glycol, CdCl2 and either CdTe powder or (Cd+Te) powder. When CdTe powder was used as a starting material for the source-layer, the electrical resistivity of the CdTe film deposited in O-2 was about one-tenth lower than that of the film deposited in He. AES, EDS and PIXE analysis showed that the Cd content in the CdTe films deposited in O-2 was Smaller than that in the CdTe films deposited in He. Especially, no oxygen element was detected in the CdTe films deposited in O-2. It turned out that the Sublimated Cd(g) and CdTe(g) from the source-layer formed cadmium oxides in O-2 and as a result the overall composition of vapor source became more Cd-deficient. The CdTe film with less Cd content increased cadmium vacancy defects (V2-Cl+ and ed V-Cd(2-)) and hole concentrations. As the Cd/Te ratio in the starting (Cd+Te) powder decreased, the ed resistivity of the CdTe films decreased and reached at a constant value of about 3x10(4) Omega . cm, regardless of deposition atmosphere. In addition, the resistivity decrease by O-2 treatment was diminished when the Cd/Te ratio was below 0.7, where the composition of CdTe film might be limited by solid solubility (Cd0.92Te1.0) The above results indicated that the resistivity decrease of CdTe films deposited in O-2 was not due to the effect of previously-known oxygen doping but due to the effect of Cd/Te compositional change. (C) 1995 American Institute of Physics.