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Low temperature photoreflectance studies of AlGaAsSb/GaSb heterostructures
C. A. Alejo-Armenta1,2 J. L. Herrera-Pérez3,4,  R. B. Pérez-Sicairos1, B. Felix-Franco1, L. N. Alejo-Armenta1,
M. C. Rivera-Morales4, and  J. G. Mendoza-Alvarez 5.
1FCFM-UAS,  Ave. de las Américas y Blvd. Universitarios, Culiacán, Sinaloa  México.
2Centro de Ciencias de Sinaloa, Ave. de las Américas 2771 Norte, Culiacán, Sinaloa, México
3Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del IPN,  Acatlán 63 Col. La Paz, 72160 Puebla, México
4Instituto de Física, Universidad Autónoma de Puebla, Apdo. Postal J-48, Puebla, México
5Departamento de Física, Cinvestav-IPN, Apdo. Postal 14-740. México 07000.


 


AlGaAsSb quaternary semiconductor layers are of great interest because their important application as the confining layers in the double heterostructure system AlGaAsSb/InGaAsSb/AlGaAsSb used for the fabrication of semiconductor lasers emitting in the medium infrared (1.6-3.7microns). The characterization of the layer crystalline quality is fundamental for these applications. Using the liquid phase epitaxy (LPE) technique, AlGaAsSb epitaxial layers were grown on GaSb substrates at temperatures around 530 C. Two types of samples were grown: one with an Al concentration of 5% where there is a direct bandgap; and the other one with an Al concentration of 27% where an indirect bandgap semiconductor is obtained. The low temperature photoreflectance (PR) technique was used in order to study the optical properties of the AlGaAsSb/GaSb heterostructures for the two aluminum concentrations used. From the fitting of the theoretical lineshape to the experimental spectra, the fundamental direct bandgap, Eo, and the broadening parameter, G, were determined as a function of the temperature in the range 15-320K. For low temperatures, Eo has a Varshni-type behavior, and from the fitting to the Varshni equation we determine the respective parameters for these type of quaternary materials. The behavior of the G parameter as a function of temperature changes drastically when the aluminum concentration in the layer increases from 5% to 27% and it can be an indication of phonon participation in the optical transitions for the samples with higher aluminum contents.


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