Galvanic Contact Deposition of CdTe Layers Using Ammoniacal Basic Aqueous Solution

The galvanic contact deposition of CdTe layers from ammoniacal basic solutions was carried out, and their deposition behaviors were investigated. The structural and electrical properties of deposits were examined and then compared with those of deposits prepared by normal electrodeposition from the same solutions. The cathode potential was always spontaneously kept at around -0.7 V vs. standard hydrogen electrode during the contact deposition although CdTe also deposited on the Cd sheet, that is, the anode. The current density gradually decreased with time just like that in the normal potentiostatic electrodeposition. The current efficiency was approximately 100% under illumination, whereas it was less than 50% in the dark. These behaviors were the same as those observed in normal electrodeposition from the same electrolytes. The resulting deposits both under illumination and in the dark were polycrystalline CdTe layers with almost stoichiometric composition. The as-deposited CdTe layer had a p-type conduction with resistivity of the order of 10(7) Omega cm.