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Raman spectra between room temperature and 350 °C were measured in GaAs layers grown by hydride vapor phase epitaxy on Si substrates using the selective conformal growth method. The contributions of the thermal expansion, anharmonic phonon decay, and strain are considered in order to analyze the Raman data. The tensile strain in the conventional GaAs/Si seed and in the conformal GaAs layers was determined from the Raman spectra. It is shown that the thin SiO2 layer between the GaAs and the Si substrate is a compliant layer that plays an important role in the reduction of the dislocation density in the conformal layers. The tensile strain in conformal layers was higher than in the conventional GaAs/Si layers, in which strain is relieved by the high density of dislocations.

Undoped GaAs layers grown on Si substrates by the conformal method were studied by micro-Raman spectroscopy, cathodoluminescence, and diluted Sirtl solution with light ͑DSL͒ etching. The results show that nonintentional doping of conformal layers can take place near the seed/layer interface. The self-doped area presents a bright luminescence emission and shows longitudinal optic-plasmon coupled Raman modes. The nonintentional dopants were n type as deduced from Raman spectroscopy and DSL selective etching. The doped region extends only 2-3 m from the seed and was tentatively associated with enhanced diffusion of Si in the presence of dislocations at the interface between the seed and the conformal layer.

Optical studies of conformal GaAs layers grown on silicon substrates were carried out by cathodoluminescence, photoluminescence imaging, and micro-Raman spectroscopy. These techniques revealed, in the conformal GaAs layers, local variations of the luminescence intensity with the shape of stripes both parallel and perpendicular to the GaAs seed, associated with local variations of tensile stress. The cathodoluminescence and micro-Raman spectra suggest that this distribution of tensile stress plays an important role in the formation of mid-gap states responsible for the variations of the luminescence intensity. The high luminescence emission of the conformal GaAs layers compared to the emission of the GaAs seed grown directly on the Si substrate is consistent with the high quality of the conformal layers.

Transparent conductive thin films on glass substrates from metal nano-wires were produced by the spin coating method by varying the speed of rotation between 1000 and 9000 RPM. Morphological and structural properties of the deposited layers were studied by Scanning Electron Microscopy (SEM). The electrical and optical properties were studied as a function of layer thickness by the Van Der Paw method and transmittance measurements in the range between 350 and 800 nm. A correlation between the thickness of the deposited layers and their electrical and optical properties is obtained, showing less sheet resistance to larger thickness while its transmittance decreases. Samples with sheet resistance of about 20 Ω/sq and with average 77% light transmittance at 550 nm were obtained. Keywords: Metal nano-wire, spin-coating, thin films, transparent conductors. ResumenSe fabricaron películas delgadas conductoras y transparentes sobre sustratos de vidrio a partir de nano-hilos metálicos por el método spin coating, variando la velocidad de rotación entre 1000 y 9000 revoluciones por minuto. De las capas depositadas se hizo un estudio de sus propiedades morfológicas y estructurales mediante microscopía electrónica de barrido (SEM). Las propiedades eléctricas y ópticas se estudiaron en función del espesor de las capas mediante el método de Van Der Paw y con medidas de transmitancia en el rango entre 350 y 800 nm. Se encuentra una correlación entre el espesor de las capas depositadas y sus propiedades eléctricas y ópticas, presentando menor resistencia de hoja a mayores espesores a la vez que su transmitancia disminuye. Se obtuvieron muestras con resistencia de hoja alrededor de 20 Ω/sq y transmitancia óptica promedio de 77% a 550 nm.

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We study doping profiles in selectively Si-doped GaAs layers grown by the conformal method. This growth technique allows to obtain GaAs/Si with optoelectronic quality. The samples are laterally grown, and selective doping with Si is carried out in such a way that doped stripes are intercalated with undoped ones. The study of the doping profiles was carried out by cathodoluminescence (CL) and micro-Raman (pR) spectroscopy. Abrupt doping profiles between doped and undoped stripes were demonstrated by monochromatic CL images. Deep level related CL bands can be observed between 1000 and 1400 nm, evidencing the complex mechanism for Si incorporation at the growth temperature (730 'C). Net doping concentrations and mobilities across the layers were determined from the analysis of the phonon-plasmon coupled modes in the pR spectra obtained with a lateral resolution better than 1 pm.

In this paper, we investigate the influence of different chemical treatments on the surface of multicrystalline Silicon (mc-Si) wafers, for both revealing grain boundaries and intra-grain defects. Electrical characterization by light beam-induced current (LBIC) was also carried out after the treatments. Several pieces of *2 9 2 cm 2 , from mc-Si wafers, were mechanically polished and chemically etched and subsequently metallized with gold (on both surfaces) by sputtering, using optimized deposition times for doing transparent electrodes suitable for LBIC mapping. The surface treatments are discussed in terms of their capabilities to reveal the crystal defects and to provide the best conditions for efficient LBIC signals directly on silicon substrates, in the absence of a p-n junction. The best surface treatments allowing both revealing crystallographic defects and permitting the measurement of highly contrasted LBIC maps is the KOH etching. A large number of intra-grain defects are clearly revealed, being their electrical activity sensitively higher than that of the grain boundaries.