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.     

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.     

Luminescence in photoconducting zinc telluride

The photoluminescent spectrum of ZnTe: Ga: Zn has been obtained over a range of temperatures from 323 to 4·2°K. Two prominent emissions are observed. One is due to an isoelectronic oxygen center and the other is due to two transitions, both involving a deep impurity level located about 0·6 eV from the conduction band. Such deep minority-carrier traps are consistent with those found in other highly photosensitive II–VI compounds.     

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.     

Excitation-spectra of the impurity photoluminescence of zinc telluride

Journal of Applied Spectroscopy -     

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.     

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.     

The nature of absorption bands in zinc oxide

Results are offered from a study of ultraviolet absorption in ZnO in its original state, after reduction, and light action as a function of time for which irradiated specimens are maintained in a vacuum and in the atmosphere. Bands at 3.36, 3.28, 3.21, 3.15, and 3.02 eV were detected, and the kinetics of change in their intensity with duration of light action are interpreted.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 32–36, July, 1985.The author expresses his gratitute to M. I. Dvoretskii for participation in the experimental studies.     

Copper,the dominant acceptor in refined,undoped zinc telluride

Comparative measurements have been made of optical absorption and photoluminescence of refined undoped and Cu in-diffused ZnTe single crystals. Strong increases in a bound exciton BE line near 2.375 eV previously identified with the electrically dominant point defect acceptor ‘a’, with binding energy E_A ? 149 meV, suggests that this acceptor is substitutional Cu_Zn. Similarly strong increases in a relatively broad band at slightly higher energy suggests the simultaneous incorporation of shallow donors, possibly interstital Cu_I. These findings indicate that intrinsic defects such as V_Zn neither control the Fermi level in refined ZnTe nor produce shallow acceptors with E_A ? 250 meV, contrary to much previous speculation.