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In this work reports results related to growth and characterization of Al x Ga 1-x As epilayers, which were grown in a metallic-arsenic-based-MOCVD system. The gallium and aluminium used precursors were trimethylgallium (TMGa) and trimethylaluminium (TMAl), respectively. By photoluminescence measurements observed, that only samples grown at temperatures above 800°C display photoluminescence. Hall measurements on the samples showed highly compensated material. Samples grown at temperatures lower than 750°C were highly resistive. Independently of the V/III ratio; the samples grown at higher temperatures were n-type. As the temperature is increased the layer compensation decreases. The Al x Ga 1-x As epilayers resulted n-type with an electron concentration of 1×10 17 cm -3 and a corresponding carrier mobility of ~2200 cm 2 /V×s. Raman spectra show vibrational bands associated to TO-GaAs-like (262 cm −1 ), LO-GaAs-like (275 cm -1 ), TO-AlAs-like (369 cm -1 ) and LO-AlAs-like (377 cm -1 ). The Raman spectra show the epilayers become more defective as the growth temperature is increased. The chemical composition was studied by SIMS exhibit the presence of silicon, carbon and oxygen as main residual impurities. The silicon concentration of ~1.0×10 17 cm -3 is very close to the carrier concentration determined by the van der Pauw measurements. The residual oxygen detected on the samples maybe responsible of the weak photoluminescence signal of the Al x Ga 1-x As layers.

This work presents the characterization of ZnTe nanolayers grown on GaAs and GaSb (100) substrates by the Atomic Layer Deposition (ALD) regime. Under certain conditions, the alternating exposition of a substrate surface to the element vapours makes possible the growth of atomic layers in a reactor where the atmosphere is high-purity hydrogen. ZnTe was grown simultaneously on GaAs and GaSb at the same run, allowing, a comparison between the effects produced by the superficial processes due to the different used substrates, thereby eliminating possible unintended changes of growth parameters. Nanolayers on GaSb maintained their shiny appearance even at temperatures near 420°C. It was found that for exposure times below 2.5 s there was not growth on GaAs, while for GaSb the shortest time was 1.5 s at 385°C. By HRXRD the peak corresponding to (004) diffraction plane of ZnTe was identified and investigated, the FWHM resulted very wide (600-800 arcsec) indicating a highly distorted lattice mainly due to mosaicity. Raman scattering shows the peak corresponding to LO-ZnTe, which is weak and slightly shifted in comparison with the reported for the bulk ZnTe at 210 cm -1 . Additionally, the measurements suggest that the crystalline quality have a dependence with the growth temperature.

It presents the characterization of rare earths (Eu,Ce)-doped CdS nanofilms that were synthesised by the growth technique chemical bath deposition (CBD) at the reservoir temperature of 70 ± 2• C. The doping of CdS with rare earths is performed by varying the synthesis time from 60 to 135 min. The rare earths molar concentration was range from 0.0 ≤ x ≤ 3.5, which was determined by energy dispersive X-ray spectroscopy. X-ray diffraction (XRD) analysis and Raman scattering reveal that CdS nanofilms showed the zinc blende (ZB) crystalline phase. The CdS average nanocrystal size was ranged from 1.84 to 2.67 nm that was determined by the Debye-Scherrer equation from ZB (111) direction, which was confirmed by transmission electron microscopy. Raman scattering shows that the lattice dynamics is characteristic of bimodal behaviour and the multipeaks adjust of the first optical longitudinal mode for the (Eu,Ce)-doped CdS, which denotes the Raman shift of the characteristic peak about 305 cm −1 of the CdS nanocrystals. The CdS nanofilms exhibit a direct bandgap that slightly decreases with increasing doping, from 2.50 to 2.42 eV, which was obtained by room temperature transmittance. The room-temperature photoluminescence of CdS shows the band-to-band transition at 2.88 eV, which is associated to quantum confinement and a dominant radiative band at 2.37 eV that is called the optical signature of interstitial oxygen. The Eu 3+ -doped CdS photoluminescence shows the dominant radiative band at 2.15 eV, which is associated to the intra-4f radiative transition of Eu 3+ ions that corresponds to the magnetic dipole transition, ( 5 D0→ 7 F 1 ).For the Ce 3+ -doped CdS the dominant radiative transition, at 2.06 eV, is clearly redshifted, although the passivation of the CdS nanofilms byCe was approximately by a factor about 21 for the best results.Keywords: CdS; Chemical bath deposition; Rare earths; cerium; europium.Se presenta la caracterización de las nanopelículas de CdS impurificadas con tierras raras (Eu,Ce) que se sintetizaron mediante la técnica de crecimiento deposición de baño químico (CBD) a la temperatura del reservorio de 70 ± 2 • C. La impurificación de CdS con tierras raras se realizó variando el tiempo de síntesis de 60 a 135 min. La concentración molar de las tierras raras fue de 0.0 ≤ x ≤ 3.5, que se determinó mediante espectroscopia de rayos X de energía dispersiva. El análisis de difracción de rayos X (XRD) y dispersión de Raman revelan que las nanopelículas de CdS mostraron la fase cristalina de zinc blenda (ZB). El tamaño medio de los nanocristales de CdS varió de 1.84 a 2.67 nm, que se determinó mediante la ecuación de Debye-Scherrer a partir de la dirección ZB (111), que se confirmó mediante microscopía electrónica de transmisión. La dispersión Raman muestra que la dinámica de la red es característica del comportamiento bimodal y el ajuste multipicos del primer modo longitudinalóptico para el CdS impurificado con (Eu, Ce), el cual denota el desplazamiento Raman del pico característico en aproximadamente 305 ...