Person: González Díaz, Germán
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First Name
Germán
Last Name
González Díaz
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Estructura de la Materia, Física Térmica y Electrónica
Area
Electrónica
Identifiers
132 results
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Now showing 1 - 10 of 132
Item Deposition of SiNx : H thin films by the electron cyclotron resonance and its application to Al/SiNx : H/Si structures(Journal of Applied Physics, 1998) Mártil de la Plaza, Ignacio; González Díaz, Germán; García, S.; Castán, E.; Dueñas, S.; Fernández, M.We have analyzed the electrical properties and bonding characteristics of SiNx:H thin films deposited at 200 degrees C by the electron cyclotron resonance plasma method. The films show the presence of hydrogen bonded to silicon (at the films with the ratio N/Si<1.33) or to nitrogen (for films where the ratio N/Si is higher than 1.33). In the films with the N/Si ratio of 1.38, the hydrogen content is 6 at. %. For compositions which are comprised of between N/Si=1.1 and 1.4, hydrogen concentration remains below 10 at. %. The films with N/Si=1.38 exhibited the better values of the electrical properties (resistivity, 6x10(13) Omega cm; and electric breakdown field, 3 MV/cm). We have used these films to make metal-insulator-semiconductor (MIS) devices on n-type silicon wafers. C-V measurements accomplished on the structures indicate that the interface trap density is kept in the range (3 - 5) x 10(11) cm(-2) eV(-1) for films with the N/Si ratio below 1.38. For films where the N/Si ratio is higher than 1.3, the trap density suddenly increases, following the same trend of the concentration of N-H bonds in the SiNx:H films. The results are explained on the basis of the model recently reported by Lucovsky [J. Vac. Sci. Technol. B 14, 2832 (1996)] for the electrical behavior of (oxide-nitride-oxide)/Si structures. The model is additionally supported by deep level transient spectroscopy measurements, that show the presence of silicon dangling bonds at the insulator/semiconductor interface (the so-called P-bN0 center), The concentration of these centers follows the same trend with the film composition of the interface trap density and, as a consequence, with the concentration of N-H bonds. This result further supports the N-H bonds located at the insulator/semiconductor interface which act as a precursor site to the defect generation of the type . Si=Si-3, i.e., the P-bN0 centers. A close relation between interface trap density, P-bN0 centers and N-H bond density is established.Item Full composition range silicon oxynitride films deposited by ECR-PECVD at room temperature(Thin Solid Films, 1999) Mártil de la Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro delSilicon oxynitride films were deposited at room temperature using the ECR-PECVD technique. Precursor gases were O(2), N(2) and SiH(4). The composition of the films can be controlled by regulating the gases flow ratio. R = (O(2) + N(2))/SiH(4) and R' = O(2)/SiH(4) have proved to be the key deposition parameters. FTIR spectroscopy, AES and ellipsometric measurements were performed in order to characterise the films. A single Si-O/Si-N stretching band is observed in the FTIR spectrum for all compositions, indicating single-phase homogeneous SiO(x)N(y) films. FWHM of the stretching band shows a maximum for the composition corresponding to the same number of Si-O and Si-N bonds. Samples cover the whole composition range from silicon nitride to silicon oxide including nitrogen-rich films, even though the gas flow ratio R " = N(2)/O(2) during deposition was small (from R " = 1.0 for SiO(1.9)N(0.04) to R " I = 6.7 for SiO(0.26)N(1.2)). Silicon oxide composition samples (SiO(2.0)) show essentially the same TR features as the thermal oxide: Si-O stretching band located at 1072 cm(-1), with a FWHM of 96 cm(-1) and a shoulder/peak ratio of 0.30, while nitrogen-rich samples (SiO(0.26)N(1.2)) show a total bonded hydrogen content below 2 x 10(22) cm(-3).Item Strong subbandgap photoconductivity in GaP implanted withTi(Progress in Photovoltaics: Research and Applications, 2018) Olea Ariza, Javier; Prado Millán, Álvaro del; García Hemme, Eric; García Hernansanz, Rodrigo; Montero, Daniel; González Díaz, Germán; Gonzalo,, José; Siegel,, Jan; López,, EstherPhotovoltaic solar cells based on the intermediate band (IB) concept could greatly enhance theefficiency of future devices. We have analyzed the electrical and photoconductivity propertiesof GaP supersaturated with Ti to assess its suitability for IB solar cells. GaP:Ti was obtained byion implantation followed by pulsed‐laser melting (PLM) using an ArF excimer laser. It was foundthat PLM energy densities between 0.35 and 0.55 J/cm2produced a good recovery of thecrystalline structure of GaP (both unimplanted and implanted with Ti), as evidenced by highmobility measured values (close to the reference GaP). Outside this energy density window,the PLM failed to recover the crystalline structure producing a low mobility layer that iselectrically isolated from the substrate. Spectral photoconductivity measurements wereperformed by using the van der Pauw set up. For GaP:Ti a significant enhancement of theconductivity was observed when illuminating the sample with photon energies below 2.26 eV,suggesting that this photoconductivity is related to the presence of Ti in a concentration highenough to form an IB within the GaP bandgap. The position of the IB was estimated to be around1.1 eV from the conduction band or the valence band of GaP, which would lead to maximumtheoretical efficiencies of 25% to 35% for a selective absorption coefficients scenario and higherfor an overlapping scenarioItem Compositional analysis of SiOxNy : H films by heavy-ion ERDA: the problem of radiation damage(Surface and interface analysis, 2002) Mártil de la Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro del; San Andrés Serrano, EnriqueFilms of SiOxNy:H were deposited at room temperature on Si substrates by the electron cyclotron resonance (ECR) plasma method. By varying the flow rates of the precursor gases SiH4, O-2. and N-2, the whole composition range between pure silicon oxide and nitride could be covered. Heavy-ion elastic recoil detection analysis (HI-ERDA) with a 150 MeV Kr-86 ion beam and time-of-flight (ToF) mass separation was applied to determine the absolute atomic concentrations of all film components, including hydrogen. Additionally, the bonding configuration of the films was studied by infrared (IR) spectroscopy. Extended ion beam exposure was found to decrease the intensity of the N-H phonon band as well as the nitrogen and hydrogen concentrations. By storing the ion scattering data event by event and by recalculating a zero-dose composition, this effect was taken into account. The corrected Hl-ERDA results revealed clear relations to the deposition parameters (e.g. the O-2/SiH4 flow ratio). The hydrogen incorporated in the films turned out to be bonded predominantly to nitrogen. The damage effects were strongest in the medium composition range. They were found to scale with the relative concentration of SiO2N2-type basic tetrahedrons, suggesting that this bonding configuration is most sensitive against irradiation during the HI-ERDA measurement. Copyright (C) 2002 John Wiley Sons, Ltd.Item A comparative study of anodic tantalum pentoxide and high-pressure sputtered titanium oxide(Journal of Materials Science: Materials in Electronics, 2003) Mártil de la Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro del; San Andrés Serrano, EnriqueIn this work we present a new method to fabricate improved TiO2 films by using a high-pressure sputtering system. In order to minimize the damage induced in the substrate surface by the ion bombardment, a high chamber pressure of 100 Pa is used, which is very much higher than typical values in conventional systems. We present results obtained by Xray diffraction and FTIR spectroscopy. Moreover, we will compare the properties of the resulting TiO2-insulator-metal capacitors with those of anodic Ta2O5. Very thin films of TiO2 have been obtained with a very promising quality for future electron device fabrication.Item Raman scattering by LO phonon-plasmon coupled modes in n-type InP(Physical Review B, 1999) González Díaz, Germán; Blanco, N.; Artús, L.; Cuscó, R.; Ibáñez, J.We have studied LO phonon-plasmon coupled modes by means of Raman scattering in n-InP for carrier densities between 6x10(16) and 1x10(19) cm(-3). A line-shape theory based on the Lindhard-Mermin dielectric function that takes into account the nonparabolicity of the InP conduction band as well as temperature and finite wave-vector effects is used to fit the Raman spectra and extract accurate values of the electron density. The results obtained from the Lindhard-Mermin model are compared with the charge density determinations based on the Drude and the hydrodynamical models, and the approximations involved in these models are discussed.Item Electrical characterization of electron cyclotron resonance deposited silicon nitride dual layer for enhanced Al/SiNx : H/InP metal-insulator-semiconductor structures fabrication(Journal of Applied Physics, 1999) Mártil de la Plaza, Ignacio; González Díaz, GermánWe report a study of metal-insulator-semiconductor (MIS) structures on InP. The interfacial state density and deep levels existing in MIS structures were measured by deep level transient spectroscopy (DLTS) technique. The electrical insulator properties were measured by current-voltage techniques. MIS structures were fabricated on InP substrates by direct deposition of silicon nitride (SiNx:H) thin films by electron cyclotron resonance chemical vapor deposition. In this work, we show that interfacial state density can be diminished, without degrading electrical insulator properties, by fabricating MIS structures based on a dual layer insulator with different compositions and with different thickness. The effect of rapid thermal annealing treatment has been analyzed in detail in these samples. Interface state densities as low as 3 x 10(11) cm(-2) eV(-1) were measured by DLTS in some structures. Conductance transients caused by disorder-induced gap states have been observed and analyzed providing some information about interface width. Finally, deep levels induced in the substrate have been investigated. Three deep levels at energies of 0.19, 0.24, and 0.45 eV measured from the conduction band have been found, and their dependence on the rapid thermal annealing process has been analyzed. (C) 1999 American Institute of Physics. [S0021-8979(99)03824-4].Item Compositional analysis of amorphous SiNx : H films by ERDA and infrared spectroscopy(Surface and interface analysis, Surface and interface analysis, 2000) Mártil de la Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro delThe composition of amorphous SiNx:H films grown by the electron cyclotron resonance (ECR) plasma method was studied by heavy-ion elastic recoil detection analysis (ERDA) with Xe-129 ion beams of 1.1 and 1.8 MeV amu(-1) and time-of-light (ToF) mass separation. This technique allows simultaneous determination of the absolute atomic concentrations and depth profiles of all involved elements, including hydrogen, Radiation damage at extended ion beam exposure was found to decrease the N/Si ratio and the hydrogen concentration, By measuring the dose dependence, this effect was quantified in order to support correction to zero dose conditions. Monitoring the damage effects by infrared (IR) spectroscopy revealed an increase of the SI-H bond density at the expense of N-H bands. The results suggest that the damage process Is initiated by breaking of N-H bonds and that recapturing of hydrogen by Si appears as an effective competitive process to hydrogen release, Combining the ERDA and IR data, the oscillator strength ratio of the N-H and Si-H stretching bands is found to be 1.4 +/- 0.2, Copyright (C) 2000 John Wiley & Sons, Ltd.Item Role of deep levels and interface states in the capacitance characteristics of all‐sputtered CuInSe2/CdS solar cell heterojunctions(Journal of Applied Physics, 1989) Mártil de la Plaza, Ignacio; González Díaz, Germán; Sánchez Quesada, Francisco; Santamaría Sánchez-Barriga, Jacobo; Iborra, E.All‐sputtered CuInSe2/CdS solar cellheterojunctions have been analyzed by means of capacitance‐frequency (C‐F) and capacitance‐bias voltage (C‐V) measurements. Depending on the CuInSe2 layer composition, two kinds of heterojunctions were analyzed: type 1 heterojunctions (based on stoichiometric or slightly In‐rich CuInSe2 layers) and type 2 heterojunctions (based on Cu‐rich CuInSe2 layers). In type 1 heterojunctions, a 80‐meV donor level has been found. Densities of interface states in the range 101 0–101 1 cm2 eV− 1 (type 1) and in the range 101 2–101 3 cm− 2 eV− 1 (type 2) have been deduced. On the other hand, doping concentrations of 1.6×101 6 cm− 3 for stoichiometric CuInSe2 (type 1 heterojunction) and 8×101 7 cm− 3 for the CdS (type 2 heterojunction) have been deduced from C‐Vmeasurements.- Project number: 283
Item Integración de la formación teórica y experimental en el área de la Electrónica mediante el desarrollo de una plataforma de demostración del comportamiento real de los circuitos desarrollados en la docencia teórica(2020) San Andrés Serrano, Enrique; González Díaz, Germán; Del Prado Millán, Álvaro; Olea Ariza, Javier; Caudevilla Gutiérrez, Daniel; Herrera Fernández, Fernando; Paz López, Antonio