Advanced Cd1-xMnxTe:Fe2+ semiconductor crystals for IR applications: The role of the composition and sin-band redshift spectra effect

Abstract

Doped semiconductor crystals of solid solution Cd_1-xMn_xTe:Fe²⁺ were grown by the high-pressure Bridgman method, covering the range of their existence as a zinc blende structure (0 < x < 0.76). The concentration of the Fe²⁺ impurities was approximately 10⁻³ wt% in all the studied samples. The structural and optical properties of the crystals were investigated, including the case of high concentrations of x  > 0.4. The correlations between the composition of solid solution crystals of Cd_1-xMn_xTe:Fe²⁺, the lattice constant, the band gap, and the maxima positions of the Fe²⁺ active ion absorption and emission spectra were found experimentally and explained physically. A theoretical model based on the principle of compositional additivity for solid solution semiconductor materials was first used for explaining the long-wavelength sin-band linear “redshift” of absorption and emission bands in the spectra of Cd_1-xMn_xTe:Fe²⁺ crystals with increasing solid solution concentration. A new effect is discovered for the differentiated redshift of the Jahn-Teller components (bands) of the total absorption spectrum. Longwavelength absorption bands have a stronger redshift than shortwavelength absorption bands. The redshifts in the maxima of the total absorption and emission spectra have shift (slope) coefficients K_ab ≈ 1.7 nm /at.% and K_em ≈ 6.1 nm /at.%, respectively. The obtained results can be used to predict and design laser media based on Cd_1-xMn_xTe:Fe²⁺ solid solution crystals while controlling the lasing range (for all Mn concentrations).