Infrared transmission of Cd1-xMnxTe crystal

The absorption edge and IR transmission of the as-grown and annealed Cd1-xMnxTe wafer were investigated. The Cd1-xMnxTe crystal was grown by the vertical Bridgman method, from which several (111) face monocrystalline wafers with area of 30 mm x 40 mm were sliced. The wafer was annealed under Cd atmosphere. The cut-off wavelength of the absorption edge obtained from the NIR transmission spectra indicates that the Mn composition within the as-grown wafer is in the range of 0.1887 <= x <= 0.2039, and the Mn variation is about 0.0152 and 0.0013 in the axial and radial directions of the wafer, respectively. The absorption coefficient of Cd1-xMnxTe (x = 0.2) deduced from the absorption edge of the NIR transmission spectrum ranges from 2.5 to 55 cm(-1). The FT-IR spectra in the wavenumber range 4000 similar to 500 cm(-1) show that the IR transmittance of the as-grown wafer is in the range of 45% similar to 55%. Annealing does not change the positions of absorption edge, which shows that the annealing treatment has no effect on the Mn composition of the wafer. IR transmittance of the annealed wafer increases to above 61% in the wavenumber range of 4000 similar to 500 cm(-1), which is close to the theoretical value of 65%.