Semi-insulating (Cd,Mn)Te:V crystals: Electrical contacts



The high-resistivity (Cd,Mn)Te is believed to be suitable to succesfully replace the commonly used (Cd,Zn)Te system as a material for manufacturing large-area X- and γ-ray detectors. The purpose of our study was to elaborate a method of preparing high quality (Cd,Mn)Te crystal plates as well as a technique of producing good electrical contacts to that material. (Cd,Mn)Te was grown using the Bridgman method. The crystals were doped with vanadium to the level of 1016 cm−3. The crystals are twinned in the (111) plane, but by slicing the crystal parallel to the twinning plane we obtained monocrystalline plates of large area (e.g. 30 × 30 mm2), which is essential for application purposes. Proper annealing of those plates in cadmium vapours allowed us to reduce the number of cadmium vacancies forming during the growth process. Due to the vanadium dopant acting as a compensating centre we obtained a semi-insulating material. In order to obtain good contacts to the (Cd,Mn)Te plates we used the method proposed initially for CdTe by Rioux et al. The ZnTe:Sb layers (∼1 μm thick) were grown on the epi-ready (Cd,Mn)Te:V plates by the MBE technique. The grown layers were p-type and formed a good electrical contact to the crystal plates. Finally – a standard technique was used to cover the ZnTe layer by a metal layer. The contacts formed on (111) surfaces of (Cd,Mn)Te were studied. We believe that the contacts to the (111) surface are important for applications. In the paper we describe techniques of preparing electrical contacts and results of their characterization. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)