RBS study of annealing effects in passivated mercury cadmium telluride

Changes in composition in passivated mercury cadmium telluride (Hg1-xCdXTe or MCT) due to annealing have been investigated using Rutherford backscattering spectroscopy (RBS). Different passivated structures such as anodic oxide/MCT, CdTe/MCT and ZnS/MCT annealed at 80 degrees C in 10(-6) Torr (parameters used during device packaging) have been studied and compared with the as-deposited samples. It is found that in as-deposited samples of anodic oxide/MCT and ZnS/MCT, the interface between the passivating layer and the MCT substrate is very sharp and composition of the capping layer remains constant throughout. Composition of the anodic oxide layer is estimated to be Hg:Te:Cd:O::0.4:1:0.25:3.35 while that of ZnS is Zn:S::0.9:1.1. In an annealed anodic oxide/MCT sample, the composition of the upper layer is different from that in the as-deposited sample and the interface is comparatively wider, while in the annealed ZnS/MCT sample the thickness of the interfacial region is found to be more than 50 nm and the composition of the remaining ZnS layer remains unaltered. The composition of the CdTe layer in both cases (as-deposited and annealed) is Cd:Te::l:l and the interface thickness of the as-deposited sample is found to be similar to 35 nm; which on annealing, increases to similar to 50 nm.