Lattice parameters and optical characterization of Cd 1− xMg xSe alloys grown by vertical gradient freezing technique

Abstract

Single crystals of Cd 1− x Mg x Se ternaries grown by the vertical gradient freezing technique are characterized by X-ray diffraction and electron probe microanalysis as well as wavelength-modulated reflectivity and photoluminescence to establish their basic structural and optical properties. In the composition range 0< x<0.40, the alloys crystallize in the wurtzite structure with lattice parameters decreasing linearly with increasing Mg concentration ( x). X-ray data considered in the context of interatomic distances yield an improved estimate of the tetrahedral covalent radius of Mg. Energy gap as a function of x increases linearly with increasing Mg concentration. The lattice parameters and the energy gap of the end member of the Cd 1− x Mg x Se wurtzite ternaries, i.e., of MgSe with the wurtzite structure, are deduced from those measurements.