Cd 1-x Be x Se and Cd 1-x Mg x Se solid solutions were grown from the melt by the high pressure Bridgman method. Optical, luminescence and photothermal properties of these materials were investigated. Spectroscopic ellipsometry was applied for determination of the spectral dependence of the complex dielectric function ( ) E ε and refractive index n(E) at room temperature in the photon energy range 0.75-6.5 eV for samples with optic axis (c-axis) perpendicular to the air-sample interface. The critical point (CP) parameters for E 0 and E 1 transitions were determined using a standard excitonic CP function to fit the numerically calculated differential spectra ∂ 2 ε 2 /∂E 2 . The dispersion of the refractive index of the alloys was modelled using a Sellmeier-type relation. The values of fundamental and exciton band-gap energies were estimated from the ellipsometric and photoluminescence measurements. The origin of luminescence in Cd 1-x Be x Se and Cd 1-x Mg x Se was discussed.

The dependence of the photocarrier radiometric ͑PCR͒ signal on the intensity of exciting superbandgap laser radiation was investigated. It was shown that the amplitude of the PCR signal exhibits a supralinear dependence on laser intensity I 0 ␤ , with nonlinearity coefficient/exponent ␤ such that 1 Յ ␤ Յ 2. The power dependence of the amplitude is an important indicator of the photoexcited carrier recombination physics in semiconductors ranging between monopolar ͑␤ = 1͒ and bipolar ͑␤ = 2͒ limits. The study was made with laser beams of varying wavelength, power, and spotsize and with semiconductor silicon wafers with different transport parameters, especially recombination lifetime. One-dimensional and three-dimensional models of the nonlinear PCR signal dependence on ␤ vs modulation frequency were developed. It was found that the conventional linear approach using ␤ = 1 is not always consistent with experimental slopes of amplitude vs power and it may yield erroneous values of the electronic transport properties. Consideration of the fundamental and second harmonic amplitudes and phases of the PCR signal showed that the physical origin of the nonlinear dependence of the PCR amplitude on laser intensity is consistent with high-optical-injection of free-carriers in the semiconductor. The value of ␤ can also be determined by the second harmonic-to-fundamental-amplitude ratio and is controlled by the carrier relaxation time dependence on the optically injected excess diffusive photocarrier density wave.Among the physical parameters of semiconductors, the electronic transport properties, namely, carrier recombination lifetime , carrier diffusion coefficient D, and front-and rear-surface recombination velocity S 1 and S 2 , have attracted great attention in semiconductor device manufacturing. Evaluation of these parameters is essential for characterizing semiconductor wafers, for defect and contamination monitoring, and for device modeling. 1 The technique of laserinduced infrared photocarrier radiometry ͑PCR͒ is an optoelectronic carrier density-wave diagnostic method for noncontact characterization of the electronic transport properties of semiconductors. This technique is a form of quantitative dynamic photoluminescence; it relies on the detection of modulated diffuse radiative emissions from semiconductors obeying Kirchhoff's law under conditions of nearthermodynamic equilibrium of an electronic solid when the latter is optically excited by intensity-modulated laser radiation with photon energy greater than the fundamental energy gap of the material. To determine the transport properties, both amplitude and phase of the PCR signal are simultaneously recorded as functions of angular modulation frequency ͑ = 2f͒ over several orders of magnitude and then fitted to suitable theoretical models ͓either one dimensional ͑1D͒ or three dimensional ͑3D͔͒ via a multiparameter fitting procedure. 2,3 To date, PCR has been developed as a linear technique, in the sense that the amplitude of the signal depends linearly on laser po...

In this work we demonstrate the ability to measure the effective infrared absorption coefficient in semiconductors by a photothermal infrared radiometry (PTR) experiment, and its correlation with the Hall carrier concentration. The amplitude and phase of the PTR signal were measured for Cd1−xMgxSe mixed crystals, with the magnesium content varying from x = 0 to x = 0.15. The PTR experiments were performed at room temperature in thermal reflection and transmission configurations using a mercury cadmium telluride infrared detector. The PTR data were analyzed in the frame of the one-dimensional heat transport model for infrared semi-transparent crystals. Based on the variation of the normalized PTR phase and amplitude on the modulation frequency, the thermal diffusivity and the effective infrared absorption coefficient were obtained by fitting the theoretical expression to experimental data and compared with the Hall carrier concentration determined by supplementary Hall experiments. A linear relationship between the effective infrared absorption coefficient and the Hall carrier concentration was found which is explained in the frame of the Drude theory. The uncertainty of the measured slope was 6%. The value of the slope depends on (1) the sample IR absorption spectrum and (2) the spectral range of the infrared detector. It has to be pointed out that this method is suitable for use in an industrial environment for a fast and contactless carrier concentration measurement. This method can be used for the characterization of other semiconductors after a calibration procedure is carried out. In addition, the PTR technique yields information on the thermal properties in the same experiment.