Influence of annealing on tellurium precipitates in (Cd,Mn)Te:V crystals

Abstract

The authors believe that (Cd,Mn)Te can be used as a material for gamma-and X-ray detectors [1]. The investigations are concentrated on producing, by Bridgman method, of high quality (Cd,Mn)Te crystals with high resistivity (10 9 Ccm).The IR pictures of the interior of the monocrystalline (Cd,Mn)Te :V platelets cut parallel to the (111) crystal planes and annealed in various conditions are discussed.As grown, undoped (Cd,Mn)Te crystals are of p-type, which is related mainly to the Cd vacancies (acting as acceptors), present in the crystal after the process of growth. Doping with vanadium atoms, which acts as compensating centres, results in a semiinsulating material (Cd,Mn)Te: V. Proper annealing of the platelets in cadmium vapours at uniform temperature allows reducing of the number of cadmium vacancies and reducing the level of the vanadium doping, required for compensation.It turned out that annealing in cadmium vapours not only decreases the concentration of the native cadmium vacancies but also improves the quality of the crystal. Infra red observations of the interior of the samples show that annealing in the temperature gradient perpendicular to the platelet causes an additional effectmigration of the tellurium precipitates toward the side which is at higher temperature.The influence of various conditions of annealing in cadmium vapours on tellurium inclusions and precipitates is shown.

Vanadium-Doped Cadmium Manganese Telluride (Cd1−x Mn x Te) Crystals as X- and Gamma-Ray Detectors

“…Details on the annealing process are given elsewhere. 9 We examined the samples after preparing the surfaces under an infrared (IR) microscope. We did not detect any noticeable Te inclusions in the bulk of the crystals, but almost all of the raw wafers had grain boundaries and twins, easily distinguished under a microscope, or even by the naked eye, by their optical contrast in light reflected from their lapped crystal surfaces.…”

Research Progress on Postgrowth Annealing of Cd1−xMnxTe Crystals

“…Then Mn and Cd atoms diffuse and react with Te to reduce Te inclusion size. Kochanowska et al [45] conducted uniform temperature annealing and temperature gradient annealing on CMT:V in Cd atmosphere. Both annealing methods reduce the concentration of Te inclusions.…”

Contacts for High-Resistivity (Cd,Mn)Te Crystals

“…We ensured their high resistivity by doping them with vanadium, a compensating dopant, in concentrations ranging from 3x10 16 to 5x10 17 cm -3 , and then annealing them in cadmium vapors that reduces the concentration of cadmium vacancies in the asgrown crystal [1]. Moreover, it lowers the number of tellurium inclusions and precipitates, as described by Kochanowska et al [14]. There are many aspects to preparing a crystal surface before depositing the contact layers.…”