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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1998 - 20002
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Author: Albrecht, M. × Has files: false ×

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    Optical properties and defect structure of MOVPE InGaN films
    (Optical Microestructuras Characterization of Semiconductors, Optical Microstructural Characterization of Semiconductors, 2000) Cremades Rodríguez, Ana Isabel; Albrecht, M.; Ulloa, J.M.; Piqueras De Noriega, Francisco Javier; Strunk, H.P.; Hanser, D.; Davis, R. F.
    A series of 100 nm thick InGaN films with In content up to 14% has been grown by MOVPE on SiC substrates. Optical characterization was carried out by means of reflectance spectrometry, photoluminescence and cathodoluminescence. Optical properties of the samples have been correlated with the microstructural properties measured by atomic force microscopy, transmission electron microscopy and X-ray diffraction data. Results indicate a dependence of the optical properties on the In content in the sample, as well as on the residual stress in the films induced by Indium incorporation. Part of the strain is reduced elastically by formation of pinholes which reach the InGaN/GaN interface, where first misfit dislocations are observed to form. Our results show that luminescence is directly correlated with the strain distribution in the layers. Pinholes are observed to act as nonradiative recombination sites for carriers, while strain relaxation around pinholes may enhance luminescence emission. We discuss the influence of strain with respect to In incorporation, the appearance of piezoelectric fields and effects due to strain induced band bending.
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    Minority carrier diffusion length in AlGaN: A combined electron beam induced current and transmission microscopy
    (Solid State Phenomena, 1998) Cremades Rodríguez, Ana Isabel; Albrecht, M.; Voigt, A.; Krinke, J.; Dimitrov, R.; Ambacher, O.; Stutzmann, M.
    Combined electron beam induced current and transmission electron microscopy measurements have been performed on both undoped and Si-doped AlGaN epitaxial films with aluminium contents x ranging from x=0 to x=0.79. TEM analysis shows the distribution and type of structural defects, the content of cubic phase and the decomposition phenomena strongly to depend on the Al content of the layers. The influence of the cubic phase on the electronic properties of the samples is discussed taking into account the high piezoelectric effect present in these alloys. The diffusion length of minority carriers has been determined by EBIC measurements and a lower limit of the lifetime has been estimated.