THIN-FILM JUNCTIONS OF CADMIUM TELLURIDE BY METALORGANIC CHEMICAL VAPOR-DEPOSITION

Polycrystalline films of cadmium telluride (CdTe) deposited by the metalorganic chemical vapor deposition (MOCVD) technique using the reaction of dimethylcadmium (DMCd) and di-isopropyltellurium (DIPTe) can be p type or n type, depending on the DMCd/DIPTe molar ratio in the reaction mixture. Extrinsic CdTe films have been deposited by using group III and group V compounds as dopants during the MOCVD process. Gallium can be incorporated into CdTe films to yield a dark resistivity of about 1000-OMEGA-cm and a carrier concentration of about 2 x 10(17) cm-3; however, the incorporation of arsenic or antimony is considerably more difficult, and low resistivity p-CdTe films cannot be obtained. Extrinsically doped CdTe films show significantly different photoluminescence spectra from intrinsic films of the same conducting type. Heterojunctions have been prepared by depositing p-CdTe films on CdS-coated SnO2:F/glass substrates. The junction properties and the post-deposition treatments have been investigated. Large-area (> 1 cm2) MOCVD CdTe thin-film solar cells of near 10% efficiency have been reported for the first time. Homojunctions have also been prepared by the successive in situ deposition of n- and p-CdTe films on SnO2:F/glass substrates, and their photovoltaic characteristics evaluated.