Person: González Díaz, Germán
Loading...
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
31 results
Search Results
Now showing 1 - 10 of 31
Item Influence of rapid thermal annealing processes on the properties of SiNx : H films deposited by the electron cyclotron resonance method(Journal of Non-Crystalline Solids, 1998) Martil De La Plaza, Ignacio; González Díaz, Germán; Martínez, F.L.; Selle, B.; Sieber, I.We have analyzed the effects of rapid thermal annealing on the composition and on the bonding and optical properties of amorphous hydrogenated silicon nitride (a-Si-x:H) thin films deposited at room temperature by the electron cyclotron resonance plasma method. Films with three different as-grown compositions have been studied, namely x = 0.97, 1.43 and 1.55, Annealing effects were related to film composition. In films with the presence of both Si-H and N-H bonds (as-grown compositions x = 0.97 and 1.43), we found that a reorganization of bonds takes place at temperatures less than or equal to 500 degrees C, where the well-known cross linking reaction Si-Si + N-H --> Si-H + Si-N occurs without detectable release of hydrogen. In the same range of temperatures, an increase of the band gap was observed and attributed to Si-Si bond substitution for Si-H, but no changes in composition were detected. At higher temperatures (T greater than or equal to 600 degrees C), the optical gap decreases and both Si-H and N-H bonds are lost along with a release of hydrogen and nitrogen. For the films with an as-gown composition x = 1.55, we observe that the release of hydrogen only occurs at temperatures above 900 degrees C, but it is not accompanied by any loss of nitrogen. An increase of the optical gap until the release of hydrogen begins and a decrease thereafter is observed.Item Deep-level transient spectroscopy and electrical characterization of ion-implanted p-n junctions into undoped InP(Journal of applied physics, 1995) Martil De La Plaza, Ignacio; González Díaz, Germán; García, S.; Martín Pacheco, Jaime Miguel; Castán, E.; Dueñas, S.Current-voltage, small-signal measurements, and deep-level transient spectroscopy (DLTS) spectra of p-n junctions made by Mg implantation into undoped InP are described. The I-V characteristics show that the dominant conduction mechanism at forward bias is recombination in the space-charge zone, whereas a thermally activated tunneling mechanism involving a trap at 0.32 eV dominates at reverse bias. Five deep levels located in the upper-half of the band gap were detected in the junctions by DLTS measurements, three of which (at 0.6, 0.45, and 0.425 eV) were found to appear due to rapid thermal annealing. The origin of the other two levels, at 0.31 and 0.285 eV, can be ascribed to implantation damage. Admittance spectroscopy measurements showed the presence of three levels at 0.44, 0.415, and 0.30 eV, all in agreement with those found by DLTS. The DLTS measurements showed that the concentration of deep levels decreased after longer annealing times, and that the concentration of deep levels due to the implantation increased after additional P or Si implantations. This explains the influence of annealing time and additional implantations on the I-V characteristics of the junctions.Item Optical spectroscopic study of the growth dynamics of radio-frequency-sputtered YBa2Cu3O(7-x) thin films(Applied physics Letters, 1992) Martil De La Plaza, Ignacio; González Díaz, Germán; Hernández Rojas, J. L.; Lucía Mulas, María Luisa; Sánchez Quesada, Francisco; Santamaría Sánchez-Barriga, JacoboAn optical spectroscopic study of the plasma produced during rf sputtering of an YBa2Cu3O7-x target was performed to analyze two basic properties of the deposition process: resputtering effects and oxidation mechanisms. Strong emissions of all the species above a value of the target voltage were found. These observations are associated to a strong secondary electron emission of the target which originates a negative self-bias of the substrate and a subsequent resputtering by argon cations. The addition of different amounts of oxygen to the discharge reveals that preoxidation in the gas phase may decrease the oxygen content in the films: the oxidation of the films is dominated by atomic oxygen.Item Structural, electrical, and optical properties of CuGaSe2 rf sputtered thin films(Journal of Applied Physics, 1990) Martil De La Plaza, Ignacio; González Díaz, Germán; Sánchez Quesada, Francisco; Santamaría Sánchez-Barriga, JacoboThin films of CuGaSe2 have been produced by rf sputtering. Compositional, structural, electrical, and optical properties are strongly influenced by growthtemperature. At substrate temperatures lower than 300 °C amorphous or poorly crystalline Se‐excess films are obtained, showing high resistivity (≊103 Ω cm) and optical transitions at 1.62, 1.80, and 2.4 eV (values lower than the single‐crystal counterparts). At the higher growthtemperatures,polycrystalline films are obtained (average grain size 0.7 μm) with lower values of resistivity (1 Ω cm), and optical transitions at 1.68, 1.90, and 2.55 eV (very close to the single‐crystal values). A hopping conduction mechanism has been detected at the lower measuringtemperature (T<150 K), and a grain boundary limited conduction process at the higher measurementstemperature (T>150 K). Structural and compositional characteristics are used to explain the behavior observed in the electrical and optical properties.Item Deep levels in p(+)-n junctions fabricated by rapid thermal annealing of Mg or Mg/P implanted InP(Journal of Applied Physics, 1997) González Díaz, Germán; Martín, J.M.; Barbolla, J.; Castán, E.; Dueñas, S.; Pinacho, R.; Quintanilla, L.In this work, we investigate the deep levels present in ion implanted and rapid thermal annealed (RTA) InP p(+)-n junctions. The samples were implanted with magnesium or coimplanted with magnesium and phosphorus. These levels were characterized using deep level transient spectroscopy (DLTS) and capacitance-voltage transient technique (CVTT). Seven majority deep levels located in the upper half of the band gap were detected in the junctions by using DLTS measurements, four of which (at 0.6, 0.45, 0.425, and 0.2 eV below the conduction band) result from RTA, while the origin of the other three levels (at 0.46, 0.25, and 0.27 eV below the conduction band) can be ascribed to implantation damage. An RTA-induced origin was assigned to a minority deep level at 1.33 eV above the valence band. From CVTT measurements, several characteristics of each trap were derived. Tentative assignments have been proposed for the physical nature of all deep levels.Item Experimental observation of conductance transients in Al/SiNx:H/Si metal-insulator-semiconductor structures(Applied physics Letters, 1997) Martil De La Plaza, Ignacio; González Díaz, Germán; Barbolla, J.; Castán, E.; Dueñas, S.; Peláez, R.; Pinacho, R.; Quintanilla, L.Room temperature conductance transients in the SiNx:H/Si interface are reported. Silicon nitride thin films were directly deposited on silicon by the low temperature electron-cyclotron-resonance plasma method. The shape of the conductance transients varies with the frequency at which they are obtained. This behavior is explained in terms of a disorder-induced gap-state continuum model for the interfacial defects. A perfect agreement between experiment and theory is obtained proving the validity of the model. (C) 1997 American Institute of Physics.Item Electrical characterization of ECR enhaced deposited silicon nitride bilayers for high quality Al/SiNx/InP MIS structure fabrication(Journal of Materials Science: Materials in Electronics, 1999) Martil De La Plaza, Ignacio; González Díaz, GermánThe interfacial state density existing in metal-insulator-semiconductor (MIS) structures was measured by deep level transient spectroscopy technique. The MIS structures were fabricated on InP substrates by direct deposition of silicon nitride (SiNxH) thin films by the electron cyclotron resonance method. In this work, we show that interfacial state density can be diminished without degrading electrical insulator properties by fabricating MIS structures based on a bi-layered insulator with different insulator compositions and different thickness. The effect of rapid thermal annealing treatment has been analysed in detail in these samples. An interface state density as low as 3x 10(11) cm(-2) eV(-1) was measured in some structures.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) Martil 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 Effect of substrate temperature in SiOxNy films deposited by electron cyclotron resonance(Journal of vacuum science & technology a: Vacuum surfaces and films, 1999) Martil De La Plaza, Ignacio; González Díaz, Germán; Prado Millán, Álvaro DelThe effect of deposition temperature on the physical properties of SiOxNy films has been studied. The films have ben deposited from mixtures of SiH4, O-2 and N-2, using the electron cyclotron resonance-chemical vapor deposition technique, with substrate temperature ranging from room temperature (50 degrees C) to 200 degrees C. When substrate temperature is increased, a slight decrease in both Si-H and N-H bond concentration is detected. A small shift (10-17 cm(-1)) in the dominant Fourier transform infrared (FTIR) absorption peak (Si-O/Si-N stretching band) seems to be associated with a decrease in the N-H bond concentration. This behavior is attributed to the formation of Si-N bonds at the expense of N-H bonds, with no significant change in the film composition. Full width at half maximum (FWHM) of the dominant FTIR peak decreases as temperature is increased for all the composition range, indicating an improvement in the quality of the films. Silicon oxide films (SiO2.0) deposited at 200 degrees C show improved properties with respect to those deposited at room temperature. FWHM decreases from 95 to 87 cm(-1), and the shoulder-to-peak ratio from 0.29 to 0.22. The position of the Si-O stretching band (1071 cm(-1)) is unaffected. These values are very close to those obtained for thermally grown oxides, while the thermal budget of the process is significantly reduced. (C) 1999 American Vacuum Society. [S0734-2101(99)01704-2].Item Conductance transients study of slow traps in Al/SiNx : H/Si and Al/SiNx : H/InP metal-insulator-semiconductor structures(Electrically based microstructural characterization II, 1998) Martil De La Plaza, Ignacio; González Díaz, Germán; Dueñas, S.; Peláez, R.; Castán, E.; Barbolla, J.We have obtained Al/SiNx:H/Si and Al/SiNx:H/InP Metal-Insulator-Semiconductor devices by directly depositing silicon nitride thin films on silicon and indium phosphide wafers by the Electron Cyclotron Resonance Plasma method at 200 degrees C. The electrical properties of the structures were first analyzed by Capacitance-Voltage measurements and Deep-Level Transient Spectroscopy (DLTS). Some discrepancies in the absolute value of the interface trap densities were found. Later on, Admittance measurements were carried out and room and low temperature conductance transients in the silicon nitride/semiconductor interfaces were found. The shape of the conductance transients varied with the frequency and temperature at which they were obtained. This behavior, as well as the previously mentioned discrepancies, are explained in terms of a disorder-induced gap-state continuum model for the interfacial defects. A perfect agreement between experiment and theory is obtained proving the validity of the model.