Person:
Cremades Rodríguez, Ana Isabel

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First Name
Ana Isabel
Last Name
Cremades Rodríguez
URI
https://hdl.handle.net/20.500.14352/75041
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Area
Ciencia de los Materiales e Ingeniería Metalúrgica
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1999 - 199912000 - 20022
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Author: Albrecht, M. × Has files: true ×

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Now showing 1 - 3 of 3
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    Study of structural defects limiting the luminescence of InGaN single quantum wells
    (Materials Science and Engineering B-Solid State Materials for Advanced Technology, 2002) Cremades Rodríguez, Ana Isabel; Piqueras De Noriega, Francisco Javier; Albrecht, M.; Stutzmann, M.; Strunk, H.P.
    InGaN quantum well (QW) structures with different thicknesses have been characterised by means of cathodoluminescence (CL) in the scanning electron microscope and transmission electron microscopy (TEM), in order to study the structural defects that limit the device operation, Misfit dislocations appear as non-radiative centres in the CL images and compete with the quantum-well related luminescence. The luminescence red shift with increasing QW thickness has been found to be influenced by composition fluctuations.
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    Effects of phase separation and decomposition on the minority carrier diffusion length in AlxGa1-xN films
    (Journal of Applied Physics, 2000) Cremades Rodríguez, Ana Isabel; Albrecht, M.; Krinke, J.; Dimitrov, R.; Stutzmann, M.; Strunk, H. P.
    Combined electron beam induced current and transmission electron microscopy (TEM) measurements have been performed on both undoped and Si-doped AlGaN epitaxial films with aluminum contents x ranging from x = 0 to x = 0.79, in order to correlate the electrical and structural properties of the films. The diffusion length of holes in the films ranges between 0.3 and 15.9 mu m, and the estimated lifetime of holes for doped samples varies between 0.2 ns and 16 mu s. Different effects contribute to the observed increase in the diffusion length with increasing aluminum content. Among others, dislocations seem to be active as nonradiative recombination sites, and phase separation and decomposition as observed by TEM in Al-rich alloys lead to the formation of a spatially indirect recombination path due to the piezoelectric field in the films. Potential fluctuations associated with these phase irregularities could also give rise to electron induced persistent conductivity contributing to the increase of the diffusion length. From our experimental observations, we conclude that the silicon dopants are partially activated in Al-rich alloys, and do not influence significantly the values of the diffusion length of holes in these samples.
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    Carrier recombination at screw dislocations in n-type AlGaN layers
    (Phisica Status Solidibi B-Basic Research, 1999) Albrecht, M.; Cremades Rodríguez, Ana Isabel; Krinke, J.; Christiansen, S.; Ambacher, O.; Piqueras De Noriega, Francisco Javier; Strunk, H. P.; Stutzmann, M.
    We analyse the recombination and scattering at dislocations in Si doped AlGaN layers by transmission electron microscopy (TEM), electron beam induced current (EBIC) and cathodoluminescence. We show that c-type screw dislocations are nonradiative recombination centres. From temperature dependent measurements of the EBIC contrast we find a shallow acceptor state 20 meV above the valence band. The level can be understood iri terms of one-dimensional dislocation bands split off by the dislocation deformation field. In addition piezoelectric potentials play a role.