Low resistance contacts to P-CuInSe₂ and p-CdTe crystals

Room temperature formation of ohmic contacts by electroplating gold on chemically treated surfaces of P-CuInSe₂ and p-CdTe single crystals is reported. The effect of Br₂/methanol and KOH+KCN+H₂O treatments prior to plating was analyzed in the case of CuInSe₂. It is shown that the former treatment yields better ohmic contacts, with lower contact resistance, than the latter. While annealing these contacts made them highly non-ohmic, the method gives reasonably ohmic contacts on surfaces, that were purposely oxidized prior to contact preparation. In the case of p-CdTe stable, low resistance ohmic contacts were obtained at room temperature by electrochemical diffusion of Hg from solution, prior to gold plating. The treatment forms a highly degenerated p⁺-HgCdTe layer. The contacts, which have a very low contact to bulk resistivity - ratio, were further improved by vacuum annealing.