Improvement of the THz response of Zn1−xMnxTe bulk crystals grown by a temperature gradient solution method

Abstract

As a type of A^II_1−xMn_xB^VI alloy, Zn_1−xMn_xTe ingots with a diameter of 30 mm are grown as large single crystals by a temperature gradient solvent method under Te-rich conditions. The orange-red Zn_1−xMn_xTe crystals are cut and processed into size-appropriate wafers for fundamental studies, as well as for THz spectroscopy and magnetization response analyses. Mn segregation associated with the growth conditions is identified in the as-grown crystals, and an enriched higher concentration of Mn is observed inside the Te inclusion. To evaluate the effect of Mn on the Zn_1−xMn_xTe crystal, the site occupation is calculated via an ab initio study, and is further confirmed by electrical and optical property measurements. Mn tends to substitute Zn to form Mn_Zn in Zn_1−xMn_xTe, which results in a low density of free charge carriers, through which the THz detection sensitivity is enhanced by 15–25% compared to the intrinsic ZnTe. Moreover, evident paramagnetic magnetization behavior is observed at variable temperatures due to the random distribution of an isolated Mn (Mn_ioct,Te6) spin with S = 5/2. We note that further optimization of the THz performance can be achieved by optimizing the growth process and tailoring the Mn content.