Formation and characterization of CdSxTe1-x alloys prepared from thin film couples of CdS and CdTe

Alloying between CdS and CdTe at the CdS/CdTe interface is a function of the growth temperature and post-deposition CdCl2 heat treatment (HT). In devices prepared by different techniques, Te-rich CdSxTe1-x alloys with x = 0.04 to 0.08 have been identified. We present our work on thin-film couples of CdS and CdTe, which can withstand higher level of CdCl2 treatment without the adhesion problems typically encountered in the regular device structure. CdS films with a thickness of similar to100 nm were deposited by chemical-bath, deposition on glass/SnO2 substrates, and CdTe films with a thickness of 300 and 800 nm were deposited by close-spaced, sublimation. The samples were treated in the presence of,vapor CdCl2 at 400degrees-450degrees C for 5 min. X-ray diffraction and optical analysis of the samples showed that S content in the CdSxTe1-x alloy increased systematically with the CdCl2 HT temperature. CdSxTe1-x alloy with x = 0.14 was identified for the samples treated at 430degreesC, which is much higher than expected from the miscibility gap at 430degreesC.