Microstructural analysis of CdTe radiation detectors with indium electrodes

In order to understand the formation mechanisms of indium contacts which were previously developed for CdTe radiation detectors with p-i-n structure, microstructure of the indium contacts which were deposited at various substrate temperatures on the p-CdTe substrates and subsequently annealed at temperature ranging from 200 to 400 degrees C were analyzed by X-ray diffraction and transmission electron microscopy. The microstructural analysis revealed that reactions between CdTe and In were enhanced by the substrate heating during deposition and growth of In4Te3 or InTe compounds on the CdTe surface was observed. Current leakage and stability of the CdTe radiation detectors were strongly correlated with the microstructure of CdTe/contact interfaces. The indium contacts, which were deposited at substrate temperature of 400 or 350 degrees C and subsequently annealed at 350 degrees C for I h in vacuum, displayed rectifying I-V behaviors and satisfied the device requirement. In addition, the excellent thermal stability of these contacts was observed. We found that the formation of the InTe compounds was essential for production of the p-i-n CdTe detector devices which require highly reliable rectifying contacts.