Magneto-optical spectroscopy of (Ga,Mn)N epilayers

We report on the magneto-optical spectroscopy and cathodoluminescence of a set of wurtzite (Ga,Mn)N epilayers with a low Mn content, grown by molecular beam epitaxy. The sharpness of the absorption lines associated to the Mn$^{3+}$ internal transitions allows a precise study of its Zeeman effect in both Faraday and Voigt configurations. We obtain a good agreement if we assume a dynamical Jahn-Teller effect in the 3d$^{4}$ configuration of Mn, and we determine the parameters of the effective Hamiltonians describing the $^{5}T\_{2}$ and $^{5}E$ levels, and those of the spin Hamiltonian in the ground spin multiplet, from which the magnetization of the isolated ion can be calculated. On layers grown on transparent substrates, transmission close to the band gap, and the associated magnetic circular dichroism, reveal the presence of the giant Zeeman effect resulting from exchange interactions between the Mn$^{3+}$ ions and the carriers. The spin-hole interaction is found to be ferromagnetic

Current-sensitive single-gun color cathode ray tube

Nonlinear phosphors for production of current sensitive single gun color cathode ray tube

Correlative study of structural and optical properties of ZnSe under severe plastic deformation

The effect of plastic deformation on the optical and structural properties of ZnSe crystals has been investigated. The optical properties have been monitored by cathodoluminescence measurements as a function of the deformation degree. Remarkable differences in the defect-related emissions from the most severely deformed areas have been encountered. Deformation of the crystal lattice of ZnSe, associated with slip phenomena, has been studied by means of Electron Backscattered Diffraction and micro-Raman spectroscopy. The relation between the deformation and the optical properties of the ZnSe crystals has been described

Electrical properties of zinc selenide

The main purpose of the research reported in this thesis was to investigate the behaviour of zinc selenide crystals doped with group III impurities such as indium and gallium, with the aim of understanding the processess of self-compensation involved which prevent them from being converted to p-type. The crystals which were grown from the vapour phase, were doped by adding the group III impurity directly to the charge in metallic form or as ZnSe:In or ZnSesGa. Measurements of the photoluminescence and cathodoluminescence revealed that the crystals behaved very similarly to copper doped ZnSe, emitting an orange-red band at 295 K and in the yellow-green and orange-red at 85 K. Measurements of the electrical conductivity and Hall coefficient were made on as-grown samples and samples heated in zinc vapour, which had been cut from ten crystal boules containing indium or gallium in concentrations between 5 and 1000 ppm. The measurements showed that the crystals obeyed the Meyer-Neldel rule and that their resistivity increased with the dopant concentration. It was also revealed, from the exponential behaviour and low values of the electron Hall mobilities, that the conduction of the lightly doped samples was via impurity centres at 295 K. The heavily doped samples also showed low values of Hall mobility limited by a combination of polar mode and ionized and neutral impurity scattering. The free electron concentration decreased while the activation energies increased with in - creasing dopant concentration. Activation energies ranged from 0.05 to 0,95 eV. The reduction of the free electron concentration with increasing indium or gallium content in the crystals, is attributed to indium (or gallium) substituting on selenium sites and forming acceptors. When the heavily doped crystals were heated in zinc the indium or gallium is precipitated. The precipitates have been examined in the optical, scanning electron and transmission electron microscopesv and are found tohave particular shapes and to decorate defects such as stacking faults. The mechanism of precipitation is discussed in same detail

Epitaxial Growth and Processing of Compound Semiconductors

Contains an introduction and reports on six research projects.Defense Advanced Research Projects Agency/U.S. Navy - Office of Naval Research University Research Initiative Subcontract N00014-92-J-1893Joint Services Electronics Program Grant DAAH04-95-1-0038National Center for Integrated Photonics Technology Contract 542-381National Science Foundation Grant DMR 92-02957MIT Lincoln Laboratory Contract BX-6085National Center for Integrated Photonics Technology Subcontract 542-383U.S. Air Force - Office of Scientific Research Grant F49620-96-1-0126U.S. Navy - Office of Naval Research Grant N00014-91-J-1956National Science Foundation Grant DMR 94-0033

Gas Source Molecular Beam Epitaxy of Compound Semiconductors

Contains an introduction and reports on seven research projects.Defense Advanced Research Projects Agency Subcontract 284-25041Joint Services Electronics Program Contract DAAL04-95-1-0038National Center for Integrated Photonic Technology Contract 542-381U.S. Army Research Office/ AASERT Contract DAAH04-93-G-0175National Science Foundation Grant DMR 92-02957Joint Services Electronics Program Grant DAAL04-95-1-0038National Science Foundation Grant DMR 90-22933National Science Foundation Grant DMR 92-02957National Center for Integrated Photonic Technology Contract 542-381MIT Lincoln LaboratoryNational Center for Integrated Photonic Technology Subcontract 542-383National Science Foundation DMR 94-0033