Growth and Characterization of (Cd, Mn)Te

The present article presents technology, required for repeatable manufacturing of the 1.5 and 2 inch crystal rods of (Cd, Mn)Te is discussed. In order to obtain semiinsultaing crystals, compensation and annealing in Cd-vapours was used. Vanadium was mainly used as the compensating dopant. The resistivity of the obtained monocrystalline plates was around 10⁹ Ω cm, and the μτ-product was about 10^-3 cm²/V. Mapping of the resistivity was performed on both as-grown crystals and the crystals annealed in the saturated Cd vapour. As-grown (undoped) crystals were inhomogeneous and their resistivities were in the range 10⁵ -10⁶ Ω cm. After annealing resistivity increased up to 1 -2 ·10⁹ Ω cm and better homogeneity could be seen. Annealing in saturated Cd-vapours had influence on tellurium inclusions/precipitates. It was studied by IR transmission microscopy. For as-grown samples the density of Te inclusions (> 1 μm) was ≈ 3 ·10⁵ cm^-3 but for annealed samples was ≈ 10⁴ cm ^-3. The concentrations (measured by SIMS) of the unintentional impurities Na, Ca, and Ga were in the region 10¹⁵ - 10¹⁶ cm^-3, corresponding well with the purity (6N) of the elements used for crystallization of our (Cd, Mn)Te. The low temperature photoluminescence (PL) measurements indicated significantly lowered concentrations of acceptors after annealing. Nearly ohmic contacts to the high resistivity (Cd, Mn)Te plates were obtained by deposition of the amorphous layers of heavily doped semiconductor (ZnTe:Sb). We undertook the present work to show that low vanadium doping level and proper annealing conditions are sufficient to obtain detector grade material.