CdTe nuclear detector electroless contact studies, new results on contact structures, interfaces and stress

Although electroless contacts are the most used contacts on II-VI semiconductor materials (CdTe family) to solve many problems, they are difficult to understand and to control. For this study, we have chosen two II-VI materials, CdTe and ZnTe, and three metals: Au, Pt and Pd. For the characterization methods we have chosen Rutherford Back-Scattering (RBS), SIMS and partially Auger for the contacts and interface structures, stoichiometry and composition profiles. Electrical measurements, PICTS and TEES, are done to find out defect level concentrations and nature, as well as the possible correlation with the composition concentrations. As first parameter change, we have chosen the solution dilution in the electroless deposition process, while the other parameters were frozen. This allows us to drive and to see a drastic variation in the profile of the metal, the 2 constituent materials and the O in the metal layer. The same has been seen at the interface where the V_Cd concentration profile shows sensible variation too. We have found a clear connection with specific electrical defect concentrations. The validity of these concentration measurements in the bulk are subject to questions, and comparison with evaporated contacts is done for bulk and surface property separations. Contact induced stress is simulated by static pressure in longitudinal and transversal direction. We have driven out the induced defect natures and concentrations. The limit of operation under stress is also given.