Effects of heat treatment on the composition and semiconductivity of electrochemically deposited CdTe films

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Abstract
Effects of heat treatments on crystalline diameter, composition, and semiconductivity of CdTe films deposited electrochemically at −0.35 V (vs Ag/AgCl) from an acidic solution containing 1‐M CdSO4 and 1‐mM TeO2 were studied. As‐grown films contained free Te in addition to CdTe. The intensity of x‐ray diffraction peaks due to CdTe became stronger by the heat treatment at higher temperatures but x‐ray diffraction peak due to metallic Te disappeared at the films annealed above 350 °C in a He atmosphere. The intensity of Auger peaks due to Cd increased and that due to Te decreased by increasing the annealing temperature. The composition of the films annealed above 350 °C was close to that of pure CdTe. The similar effects were observed at the films annealed at 350 °C for various heat treatment periods in a He atmosphere. The change of semiconductivity of the films from p to n type was observed at the films annealed at enough high temperatures and for enough long time. The disappearance of free Te from the films was explained in terms of the temperature dependence of vapor pressure of Te2 from CdTe and metallic Te.