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CdSeTe/CdMgTe double heterostructures were produced with both n-type and unintentionally doped absorber layers. Measurements of the dependence of photoluminescence intensity on excitation intensity were carried out, as well as measurements of time-resolved photoluminescence decay after an excitation pulse. It was found that decay times under very low photon injection conditions are dominated by a non-radiative Shockley-Read-Hall process described using a recombination center with an asymmetric capture cross section, where the cross section for holes is larger than that for electrons. As a result of the asymmetry, the center effectively extends photoluminescence decay by a hole trapping phenomenon. A reduction in electron capture cross section appeared at doping densities over 1016cm-3. An analysis of the excitation intensity dependence of room temperature photoluminescence revealed a strong relationship with doping concentration. This allows estimates of the carrier concentration to be made through a non-destructive optical method. Iodine was found to be an effective n-type dopant for CdTe, allowing controllable carrier concentrations without an increased rate of non-radiative recombination. [ABSTRACT FROM AUTHOR]

A noncontact, nondestructive optical quenching method is used to determine copper concentration in bulk CdTe and Cd1-xZnxTe samples. This method depends on the ability to detect copper photoluminescence emission and employs infrared light source along with the band-gap excitation beam. Acceptor-related lines are differentiated from donor-related lines with the help of this optical quenching technique.

A major challenge in the stoichiometric growth of complex oxide compounds is the control of the relative compositions of the constituent materials. A potential avenue for compositional analysis during growth is the use of x-ray fluorescence generated during reflection high energy electron diffraction measurements. Using this technique, relative compositions of Y and Mn in molecular beam epitaxy grown YMnO3 samples were studied. Comparing the results with Rutherford back scattering spectroscopy suggests that the technique has the potential for real-time analysis of elemental fluxes and stoichiometry control during sample growth. [ABSTRACT FROM AUTHOR]

The angular dependence of the x-ray fluorescence from Y and Mn inner K shell ionization induced by a grazing angle incident electron beam in several multilayered Y/Mn structures was analyzed using the distorted-wave approximation. Estimates of structural parameters, thickness, and interfacial roughness were obtained from the x-ray fluorescence measured in the total reflection regime and compared with ex situ x-ray reflectivity results. Although the sensitivity to the surface and interface roughness was relatively low, the thickness values for both single and buried layers were in good agreement with the x-ray reflectivity measurements. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) from undoped and chromium-doped ZnTe epilayers was studied in the spectral range from 0.3 to 2.4 eV over the temperature range from 5 K to room temperature. Films approximately 2 μm thick were grown by molecular-beam epitaxy on GaAs substrates. For undoped ZnTe, spectra are dominated by a sharp acceptor-bound-exciton line related to arsenic, with only weak emission observed due to substitutional oxygen (OTe). An analysis of strain-induced shifts in excitonic energies was performed to clarify transition assignments for two PL bands near 2.375 and 2.379 eV. For ZnTe:Cr epilayers, the infrared Cr2+ emission near 2.5 μm (0.5–0.6 eV) was found to be a function of both doping concentration and Zn/Te beam-equivalent-pressure ratio. Direct excitation of the Cr2+ ions with 1.89-μm light produced emission up to room temperature. Indirect excitation with 514.5-nm light produced emission that could be detected up to 180 K. Luminescence decay curves measured from a ZnTe:Cr film ([Cr]∼1×1018 cm-3) using pulsed excitation at 355 and at 532 nm indicated two lifetimes: τ1=3 (±1) μs and τ2>=10 μs. The shorter lifetime agrees with values reported previously for Cr-doped ZnTe bulk crystals and thin films under 1.9-μm pulsed excitation. [ABSTRACT FROM AUTHOR]

Using spectroscopic ellipsometry, the temperature-dependence of the dielectric functions of a series of Hg1−xCdxSe thin films deposited on both ZnTe/Si(112) and GaSb(112) substrates were investigated. Initially, for each sample, room-temperature ellipsometric spectra were obtained from 35 meV to 6 eV using two different ellipsometers. Subsequently, ellipsometry spectra were obtained from 10 K to 300 K by incorporating a cryostat to the ellipsometer. Using a standard inversion technique, the spectroscopic ellipsometric data were modeled in order to obtain the temperature-dependent dielectric functions of each of the Hg1−xCdxSe thin films. The results indicate that the E1 critical point blue-shifts as a function of Cd-alloy concentration. The temperature-dependence of E1 was fitted to a Bose-Einstein occupation distribution function, which consequently allowed us to determine the electron-phonon coupling of Hg1−xCdxSe alloys. From the fitting results, we obtain a value of 17 ± 2 meV for the strength of the electron-phonon coupling for Hg1−xCdxSe alloy system, which compares nominally with the binary systems, such as CdSe and CdTe, which have values around 38 meV and 16 meV, respectively. This implies that the addition of Hg into the CdSe binary system does not significantly alter its electron-phonon coupling strength. Raman spectroscopy measurements performed on all the samples show the HgSe-like transverse optic (TO) and longitudinal optic (LO) phonons (∼ 130 cm−1 and ∼ 160 cm−1, respectively) for all the samples. While there is a slight red-shift of the HgSe-like TO peak as a function of the Cd-concentration, HgSe-like LO peak does not significantly change with the alloy concentration. [ABSTRACT FROM AUTHOR]

Presents a study that investigated photoluminescence from heteroepitaxial (211)B cadmium telluride grown on (211)B gallium arsenide by molecular beam epitaxy. Methods used in the preparation of the samples; Analysis of the edge photoluminescence emission region; Common method of evaluating layer quality by the photoluminescence technique.