Optical properties of zinc telluride with cadmium telluride submonolayers

Reflection, luminescence, and Raman spectra of epitaxial ZnTe layers nominally incorporating double CdTe submonolayers were studied. The band of an exciton localized at the potential produced by narrow-gap planar inclusions dominated the luminescence of these heterostructures. The emission parameters of localized excitons (specifically, the ratio of integral emission intensity to localization energy) were determined, and it was found that excitons interact with longitudinal optical phonons of the layer enriched with cadmium. Giant amplification of the Stokes component resonant with the localized exciton level was observed in Raman scattering.     

Copper and native defects in zinc telluride

Zinc telluride crystals were grown from tellurium-rich solutions containing 10¹⁷–10²⁰ cm^?3 atoms of copper. The copper concentrations in these crystals were measured by activation analysis. Hall effect and resistivity measurements were performed. Photoluminescence spectra were also determined. Our interpretation of the different results is that copper brings about both acceptor defects Cu_Zn with a 0·12–0·13 eV ionization energy, and donor defects. The second acceptor level of the zinc vacancy was found to be at 0·15 eV.     

Excited donor and acceptor states in zinc telluride

Excited shallow donor and acceptor states are observed in excitation spectra of donoracceptor pair luminescence in ZnTe. The experiments yield a donor ionization energyE _D =18.3±0.3 meV, and from the Li acceptor 2P _3/2, 2P _5/2( ₈), and 2P _5/2( ₇) states valence band parametersµ=0.60±0.10 and=0.22±0.05. The latter exceeds values derived from other experiments and indicates considerable nonspherical perturbations associated with this acceptor requiring an extension of existing theories for shallow acceptor states.     

Mercury zinc telluride longwavelength high temperature photoconductors

The use of the mercury zinc telluride (MZT) alloy system for longwavelength photoconductors, operating in the 200–300 K temperature range, is reported. The generalized figure of merit and the ultimate performance of MZT 10.6 μm photoconductor have been calculated for various temperatures as a function of composition and doping. High temperature photoconductors have been fabricated from p-type doped bulk crystals grown by the quench/anneal technique.     

Spin-flip light scattering from phosphorous acceptors in zinc telluride

Three spin-flip transitions in ZnTe:P are interpreted in terms of the shallow acceptor Hamiltonian of Bir, Butikov, and Pikus.     

Optical properties of zinc telluride in vacuum ultraviolet region

Reflectance spectra in the photon energy range between 15 and 150eV were measured on zinc telluride single crystals by using synchrotron radiation. A peak associated with transitions from the 3d core level of Zn to the conduction band was observed. A sharp doublet related to the 4d of Te was also observed. The optical constants including the complex index of refraction and the complex dielectric constant were determined on the basis of the Kramers-Kronig analysis.     

Diffusion and lattice location of lithium in zinc telluride

The diffusion of Li in ZnTe has been investigated in the temperature range 400–700°C by use of nuclear analysis and chemical or ion beam etching techniques. The penetration profiles are complex and most of them were found to show three regions. The experimental results are interpreted as a superposition of different diffusion mechanisms: one where the impurity diffuses simultaneously in substitutional and interstitial forms, the interstitial form being trapped at defects, and the other which involves short-circuit paths. Activation energies and diffusion constants D_o were measured. Furthermore the channeling technique was used for lattice location. This revealed that (60–80)% of the lithium atoms occupy the zinc substitutional site following annealing at 500°C.     

Excitation-spectra of the impurity photoluminescence of zinc telluride

Journal of Applied Spectroscopy -     

Luminescence of the cadmium telluride quantum dots in the porous silicon oxide

The luminescence of the CdTe quantum dots deposited on glass substrate and introduced into the porous silicon oxide matrix is investigated. The experimental results on the photoluminescence with one- and two-photon excitation and cathodoluminescence indicate that the quantum dots introduced into the matrix retain the luminescence properties. The coefficient of the two-photon absorption of the CdTe quantum dots on the glass substrate is determined.     

Improved diode properties in zinc telluride thin film-silicon nanowire heterojunctions

In this study, structural and optoelectronic properties and photodedection characteristics of diodes constructed from p-zinc telluride (ZnTe) thin film/n-silicon (Si) nanowire heterojunctions are reported. Dense arrays of vertically aligned Si nanowires were successfully synthesized on (1 1 0)-oriented n-type single crystalline Si wafer using simple and inexpensive metal-assisted etching (MAE) process. Following the nanowire synthesis, p-type ZnTe thin films were deposited onto vertically oriented Si nanowires via radio frequency magnetron sputtering to form three-dimensional heterojunctions. A comparative study of the structural results obtained from X-ray diffraction and Raman spectroscopy measurements showed the improved crystallinity of the ZnTe thin films deposited onto the Si nanowire arrays. The fabricated nanowire-based heterojunction devices exhibited remarkable diode characteristics and enhanced optoelectronic properties and photosensitivity in comparison to the planar reference. The electrical measurements revealed that the diodes with nanowires had a well-defined rectifying behaviour with a rectification ratio of 10⁴ at ±2 V and a relatively small ideality factor of n = 1.8 with lower reverse leakage current and series resistance at room temperature in dark condition. Moreover, an open-circuit voltage of 100 mV was also observed under illumination. Based on spectral photoresponsivity measurements, the nanowire-based device exhibited a distinct responsivity and high detectivity in visible and near-infrared (NIR) wavelength regions. The device characteristics observed here offer that the fabricated ZnTe thin film/Si nanowire-based p–n heterojunction structures will find important applications in future and will be a promising candidate for high-performance and low-cost optoelectronic device applications, NIR photodedectors in particular.     

Luminescence of tungsten centers in zinc selenide

Luminescence spectra of W centers in ZnSe are studied. Radiative d–d transitions are identified by the Tanabe–Sugano diagram of the crystal field theory. It is found that the type of electronic transitions changes with a significant change in spectral characteristics of impurity radiation during the transition fromthe 3d- to 5d-electronic systemof impurity centers in the crystals under study.