Bridgman growth and electric breakdown behavior of Vanadium-Zinc codoped Cadmium Telluride

摘要

Photorefractive vanadium-zinc codoped Cadmium Telluride has been grown by the vertical Bridgman method under varied experimental conditions (with or without vertical magnetic field and with or without cadmium overpressure). Ingots with large single crystals, typically of the order of 1 cm~3, were obtained with a resistivity of about 10~(10) Ωcm. Infrared microscopy shows few tellurium secondary phases (precipitates and inclusions) when using cadmium overpressure. In this case residual absorption is low. The aim of our study was to investigate the electric breakdown behavior of vanadium-zinc codoped cadmium telluride under a 5-10 kV/cm electric field. Indeed such electric field allows to dramatically enhance the photorefractive response of the crystal. Induced electro-optic inhomogeneities inside our crystals were probed using a polarimetric method (with a collimated Nd:YAG laser beam -1.064 μm) coupled with a CCD camera which gives us the ability to have a global view of our sample and to accurately localize the breakdown. We mainly concentrate our attention on surface problems, on regions near contacts and on reproducibility of the latter.