Person: Díaz-Guerra Viejo, Carlos
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First Name
Carlos
Last Name
Díaz-Guerra Viejo
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de Materiales
Area
Física Aplicada
Identifiers
5 results
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Now showing 1 - 5 of 5
Item Technical developments and principal results of vertical feeding method for GaSb and GaInSb alloys(Thermophotovoltaic Generation of Electricity, Thermophotovoltaic Generation of Electricity, 2007) Vincent López, José Luis; Díaz-Guerra Viejo, Carlos; Piqueras de Noriega, Javier; Dieguez, E.In this work, the experimental set-up of the Vertical Feeding Method (VFM) which has been used for the preparation of GaSb and GaInSb materials is presented. The different elements of the set-up are detailed as well as the preparation process. The different configurations that have been used for material production are briefly described and the principal results are summarized. In the case of Te-doped GaSb materials, the study, focused on the grain size and structure of the as-grown materials, showed that single crystals can be obtained with the VFM. In the case of GaInSb materials, the study, focused on the spatial indium distribution in the solid phase prepared with the different VFM configurations, showed that an effective band edge reduction can be achieved.Item Characterization of undoped and Te-doped GaSb crystals grown by the vertical feeding method(Journal of Crystal Growth, 2006) Vincent, J.; Díaz-Guerra Viejo, Carlos; Piqueras de Noriega, Javier; Amariei, A.; Polychronladis, E.K.; Dieguez, E.Undoped and Te-doped GaSb ingots have been grown by the vertical feeding method. The structural, optical and electrical properties of the grown crystals were respectively investigated by X-ray diffraction, transmission electron microscopy, cathodoluminescence spectroscopy and Hall effect measurements. Undoped samples show good crystalline and electrical properties. Te-doped material presents a clear polycrystalline character and a deviation from axial segregation laws found for crystals grown by classical techniques. The obtained results allow us to draw some conclusions about the solidification mechanism associated to the growth conditions used in our feeding experiments.Item Solidification features of cast and vertically fed Te-doped GaSb materials(Journal of Crystal Growth, 2006) Vicent López, José Luis; Díaz-Guerra Viejo, Carlos; Piqueras de Noriega, Javier; Dieguez, E.Dilute Te-doped GaSb alloys have been prepared by the vertical feeding method (VFM) using both casting and feeding configurations. The structural and optical properties of the samples were characterized by etching, X-ray diffraction and cathodoluminescence in the scanning electron microscope. The obtained results confirm the variation of the segregation coefficient k observed in previous VFM Te-doped GaSb experiments. The increase of k and the grain structure refinement are attributed to the increase of the interface velocity. The feeding configuration of the VFM seems to be the most appropriate one to control segregation and grain size for Te-doped GaSb alloys.Item Influence of doping level on the cathodoluminescence of Se-doped GaSb crystals(Journal of Physics D-Applied Physics, 2007) Díaz-Guerra Viejo, Carlos; Vicent López, José Luis; Piqueras de Noriega, Javier; Dieguez, E.The influence of the doping level on the radiative recombination properties of GaSb:Se crystals has been investigated by cathodoluminescence (CL) microscopy and spectroscopy in the scanning electron microscope. CL images evidence a high dislocation density and dopant segregation around the dislocation cores in highly-doped crystals. A progressive reduction of the Se content leads to a lower dislocation density and a more uniform luminescence spatial distribution. CL spectra reveal the existence of three Se-related emission bands, centred in all the samples investigated at about 765, 740 and 719 meV, whose relative intensity is influenced by the doping level. Measurements carried out at different temperatures and excitation densities indicate that these bands can be attributed to transitions from the conduction band to deep acceptor levels.Item Cathodoluminescence characterization of InGaSb crystals(2004 24th International Conference on Microelectronics, Proceedings, Vols 1 and 2, 2004) Chioncel, M.F.; Díaz-Guerra Viejo, Carlos; Piqueras de Noriega, Javier; Vincent López, José Luis; Bermudez, V.; Dieguez, E.The nature and the spatial distribution of radiative defects in In(X)Ga(1-x)Sb grown by the vertical Bridgman method have been studied by cathodoluminescence (CL) in a scanning electron microscope. The CL results have been complemented by X-ray microanalysis and backscattered electron imaging to relate the local luminescence properties to the chemical composition. Measurements of the band gap energy from the CL spectra, supported by X-ray compositional mappings, reveal an effective incorporation of In in the matrix, leading to the fori-nation of the ternary alloy in the whole volume of the ingot. A band often observed in the CL spectra, peaked at about 20 meV below the band gap energy, is attributed to the presence in the ternary alloy of an acceptor level that would correspond to the V(Ga)-Ga(Sb) acceptor in GaSb.