Growth, Characterization And In Doping Of Cd_1-xMn_xTe Crystals

Cd_1-xMn_xTe is a dilute magnetic semiconductor with zinc blende structure for the composition region x<0.77, where the magnetic atom Mn²⁺ randomly substitute Cd²⁺ sites. First, by using its unique magnetic and magneto-optic properties, a number of devices based on Cd_1-xMn_xTe crystals, such as Faraday rotators, optical isolators, solar cells, and magnetic field sensors, have been developed. Secondly, Cd_1-xMn_xTe crystals can be used as substrates for the epitaxial growth of HgCdTe and HgZnTe, due to its variable lattice constant α in between 6.37 A and 6.48 A as a function of the Mn content to match the lattice of the epitaxy layer. Thirdly, Cd_1-xMn_xTe is demonstrated to be a good candidate for the X-ray and y-ray detector to compete with Cd_1-xZn_xTe, because Mn distributes more homogeneously than Zn in the crystal and Mn increases the bandgap twice as fast as Zn. For all those applications, Cd_1-xMn_xTe crystals with high crystalline perfection are required.In this paper, we report the growth of Cd_0.8Mn_0.2Te crystal ingots by Vertical Bridgman (VB) method. The growth procedure was carefully controlled to avoid the solid phase transition and twin formation. The crystalline quality of the ingots was evaluated with X-ray diffraction. Mn concentration distribution along axial and radial direction was also analyzed in detail. The resistivity and IR transmittance was assessed using I-V and IR transmission measurements. Chemical etching was applied to reveal the crystal defects, such as, dislocations, Te inclusions and twins. The formation principles of these defects and methods...