Cu(In,Ga)Te₂ film growth by a two-stage technique utilizing rapid thermal processing

Cu(In,Ga)Te₂ (CIGT) thin films doped with Na were grown using a two-stage technique. During the first stage of the process precursor layers were formed over Mo coated stainless steel foil substrates by electrodeposition of Cu, In and Ga and evaporation of a NaF film as a dopant and Te. During the second stage, the foil/Mo/(Cu, In, Ga)/NaF/Te stacks were reacted by rapid thermal processing. The ramp rate to the reaction temperature of 600 °C was changed between 0.5 and 10 °C s⁻¹. Resulting compound layers were analyzed to evaluate the effect of the temperature ramp rate on film quality. It was found that a secondary phase of InTe that was detected in films reacted at ramp rates of 0.5–5 °C s⁻¹ was not present for the films reacted at a ramp rate of 10 °C s⁻¹. Film morphology of the fast ramp rate sample showed improved crystallinity and grain size, which was superior compared to others. Gallium gradation was detected through all the layers irrespective of the temperature ramp rate, surface of the films being more In-rich. (paper)