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

Abstract

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 10 16 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 mm 2 ), 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.

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

“…Research of the growth of cadmium manganese telluride (Cd,Mn)Te crystals doped by vanadium, carried out in the Institute of Physics, Polish Academy of Sciences (IP PAS), is focused on the Bridgman growth from the melt [1], [4]. Dopant is used because we want to obtain a high-resistivity (p~10 9 ) material for construction of the X-and gamma-ray detectors.…”

Amorphous contact layers on (Cd,Mn)Te crystals

“…Selective etching creates a tellurium-rich layer of about 20Å thick. One can find more details of this type of etching in [20,22]. Deposition of the amorphous semiconductor contact layers was performed in the MBE apparatus (used just as a good evaporator).…”

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

“…1 illustrates the distribution of atoms in this layer. This type of etching is detailed in [1] and [15].…”

“…10 shows the sharp lines of the reflections from the monocrystalline contact layer. [15] (222) and (444)) grown on the (Cd,Mn)Te (for (333)) crystal plate. [15].…”