V. S. Vavilov

Bound-exciton emission bands in ZnSe single crystals and mixed plasmon-phonon modes

The paper reports a cathodoluminescence study of ZnSe single crystals annealed in a Bi melt at 1200 K for 120 h. It is found that the distance between the phonon structure satellites in the bound-exciton series I1s-nLO and I1d-nLO and the relative satellite intensity are different in samples with different conduction electron concentrations. It is shown that this difference is due to the mixing of the plasmon and phonon modes. The shape of the bound-exciton emission spectrum in ZnSe crystals in the 450–470 nm region is calculated, and a satisfactory agreement with the experiment calculations is obtained.

Cathodoluminescence of ZnSe(Bi):Al crystals

The cathodoluminescence (CL) in ZnSe crystals annealed at T=1200 K in a Bi melt containing an aluminum impurity is investigated. The spectra are recorded for different excitation levels, temperatures, and detection delay times t0. As t0 is increased, the intensity of the orange band at λmax=630 nm (1.968 eV) in the CL spectrum decreases in comparison to the intensity of the dominant yellow-green band at λmax=550 nm (2.254 eV), whose half-width increases in the temperature range 6–120 K and then decreases as the temperature increases further. It is shown that such behavior of the yellow-green band is caused by the competition between two processes: recombination of donor-acceptor pairs and of free electrons with holes trapped on acceptors. The former mechanism is dominant at low temperatures, and the latter mechanism is dominant at high temperatures. At T∼120 mK the contributions of the two mechanisms to the luminescence are comparable. The resultant structureless band then achieves its greatest half-width, which is dictated by the interaction of the recombining charge carriers with longitudinal-optical and longitudinal-acoustic phonons and with the free-electron plasma. The mean number of longitudinal-optical phonons emitted per photon is determined mainly by their interaction with holes trapped on deep acceptors in the form of Al atoms replacing Se. The donor in the pair under consideration is an interstitial Al atom.

Electron irradiation of lithium doped germanium at cold temperatures

Abstract Slices, cut from antimony or arsenic doped n-type germanium ingots, were additionally doped with various lithium impurity concentrations. Samples, suited for Hall effect and minority-carrier diffusion-length measurements, were then irradiated by 1 MeV electrons at 78 or 125 °K and after that in some cases were annealed isochronally. No differences in carrier removal or lifetime damage rates between lithium doped and conventional n-type crystals were found up to 200–230 °K. Hall mobility and lifetime in irradiated lithium doped samples recovered substantially at the annealing temperatures ranges of 240–320 °K and 200–280 °K, respectively, that is at much lower temperatures, than in the crystals without lithium. No Ec − 0.20 eV acceptor level radiation defects were observed in the samples with large lithium impurity concentrations.

A new bound-exciton emission band in ZnSe crystals and multiplasmon optical transitions

We have investigated cathodoluminescence both in unannealed ZnSe crystals and in crystals annealed in a Bi melt at a temperature of 1200K for 120 h with subsequent quenching. In the wavelength range 450–480 nm we have detected a new line series Iis-nLO-mPl consisting of the bound-exciton emission line Iis with wavelength λ=455.9 nm and its plasmon and LO-phonon echoes Iis-LO (λ1=461.3 nm), Iis-2LO (λ2=466.8 nm), Iis-3LO (λ3=472.4 nm), and Iis-4LO (λ4=478.3 nm). We have determined the mean number of emitted LO phonons NLO=2.2±0.1 per photon. It is shown that the observed finer structure of the band may be due to multiphonon optical transitions. At low plasma densities (ωp≪ωLO) the Coulomb interaction causes broadening of the Iis-nLO series. In samples with denser plasma, in which the condition ωp⩽ωLO is met, multiplasmon satellites of the series Iis-nLO-mPl are observed. Theoretical calculations of the shape of the emission band agree with experiment.

A series of free exciton lines in zinc diarsenide

A structure corresponding to the n=1, 2, and 3 free-exciton states is observed in the optical transmission spectra of zinc diarsenide at 5 K. The band gap for E⊥C at temperatures of 5–300 K and the exciton binding energy (17.5 eV) are determined.

Cathodoluminescence spectroscopy of diamond films and ceramics

Abstract Cathodoluminescence spectra of diamond ceramics, polycrystalline diamond films and diamond-like films were measured at 77 and 300 K. The results obtained are compared and discussed. A qualitative interpretation of basic features is performed.

Subthreshold energy electron beam annealing of tin-implanted silicon

Abstract 150 keV energy tin ions were implanted in silicon to monitor Mossbauer Effect. The resultant tin-silicon solid solution was subjected to thermal and radiation annealing. Mossbauer spectra reveal that high intensity subthreshold energy electron irradiation leads to disintegration of the solid solution similar to the thermal process.