Víctor Hugo Méndez García - Academia.edu (original) (raw)

Papers by Víctor Hugo Méndez García

応用物理学関係連合講演会講演予稿集(CD-ROM), 2010

physica status solidi (a), 2009

Journal of Crystal Growth, 2013

ABSTRACT In this work, we present a Raman scattering study of GaAs layers grown on (6̄3̄1̄)-orien... more ABSTRACT In this work, we present a Raman scattering study of GaAs layers grown on (6̄3̄1̄)-oriented substrates by molecular beam epitaxy. A set of samples whose morphology sustained different corrugation order were grown by MBE by varying the growth parameters such as temperature and As/Ga flux ratio. We employed polarized Raman spectroscopy using the backscattering configurations Z(XX) , Z(XY) and Z(YY) . According to the calculated dipole selection rules both TO and LO phonons are allowed for backscattering from a perfect GaAs (6̄3̄1̄) crystal, but with the intensity of the TO phonon much larger than that of the LO phonon. However, it is found that the selection rules differ for corrugated samples. Besides, the TO/LO phonon resonances intensity ratio and the LO peak asymmetry depend on the corrugation order of the samples.

Electromagnetic Materials and Devices, Jan 22, 2020

This chapter is dedicated to study the semiconductor surface states, which combined with nanolith... more This chapter is dedicated to study the semiconductor surface states, which combined with nanolithography techniques could result on remarkable properties of advanced nanodevices suitable for terahertz (THz) signal detection or harvesting. The author presents the use of low-dimensional semiconductor heterostructures for the development of the so-called self-switching diodes (SSDs), studying by simulation tool key parameters in detail such as the shape and size of the two-dimensional electron gas system. The impact of the geometry on the working principle of the nanodevice and the effects on current-voltage behavior will be described in order to acquire design guidelines that may improve the performance of the self-switching diodes when applied to low-power square-law rectifiers as well as elements in rectennas by appropriately setting the size of the components.

Applied Physics Letters, 2021

We present an experimental study of the terahertz emission from In x Ga 1Àx As epitaxial layers t... more We present an experimental study of the terahertz emission from In x Ga 1Àx As epitaxial layers that were grown while varying the alloy fraction x. We observe the terahertz emission that is significantly different depending on the variation direction of the alloy fraction. We attribute the difference to the significant change of the band bending induced in the growth direction and to the position-dependent variation of the effective mass.

Thin Solid Films, 2020

Photoreflectance and ellipsometry are two very useful optical spectroscopy techniques employed to... more Photoreflectance and ellipsometry are two very useful optical spectroscopy techniques employed to analyze the electronic band structure of semiconductors. Photoreflectance and ellipsometry spectra of gallium arsenide nitride (GaNAs) thin films on gallium arsenide (GaAs) layers may be composed of transitions from the conduction bands of the alloy and the binary (E-, E + , and E 0 , respectively) in conjunction with their interaction spin-orbit split-off valence band (E-+Δ 0 and E 0 +Δ 0). For low concentration of nitrogen (between 0.2 and 0.6 %), the determination of the E + conduction band becomes difficult to distinguish by the fact that critical points are superimposed in the spectrum of both characterization techniques. In this work, a method to determine the E + conduction band of GaNAs thin films grown on GaAs by molecular beam epitaxy is proposed when the overlapping of spectral features influences their optical determination. When using spectroscopic characterization techniques, the modulation/excitation region depends on the wavelength employed and sample characteristics, and consequently low nitrogen concentration in the alloy in conjunction with the thickness of the GaNAs layers have been found responsible for the signal overlapping. It is demonstrated that by decreasing the sample temperature in the photoreflectance process the overlapping is avoided, allowing for a correct interpretation of the GaNAs conduction band splitting analysis and discarding the contribution of built-in electric fields. From these results, we achieved a precise experimental determination of the presence/absence of the band splitting predicted by the band anti-crossing model using non-destructive characterization tools.

AIP Advances, 2016

Energetically unstable crystalline surfaces, among their uses, can be templates for the growth of... more Energetically unstable crystalline surfaces, among their uses, can be templates for the growth of periodic arrays of one-dimensional (1D) nanoscale structures. However, few studies have explored self-assembled faceting on high-index (HI) planes inside the stereographic triangle, and extant studies have not produced any criteria for encouraging the formation of one-dimensional periodic arrays. In this Letter, by analyzing the MBE growth of homoepitaxial facets on (631)A GaAs, a HI plane inside the triangle, we present a criteria to produce highly uniform 1D periodic arrays on unexplored surfaces. These families of planes are those belonging to the lines connecting the energetically stable HI GaAs (11 5 2) plane with any of the (100), (110), and (111) planes at the corners of the stereographic triangle. This novel strategy can lead to new possibilities in self-assembling 1D structures and manipulating physical properties, which in turn may result in new HI-and 1D-based experiments and devices.

AIP Advances, 2015

In this letter, self-switching nanochannels have been proposed as an enabling technology for ener... more In this letter, self-switching nanochannels have been proposed as an enabling technology for energy gathering in the terahertz (THz) regime. Such devices combine their diode-like behavior and high-speed of operation in order to generate DC electrical power from high-frequency signals. By using finite-element simulations, we have improved the sensitivity of L-shaped and V-shaped nanochannels based on InAlAs/InGaAs samples. Since those devices combine geometrical effects with their rectifying properties at zero-bias, we have improved their performance by optimizing their shape. Results show nominal sensitivities at zero-bias in the order of 40 V −1 and 20 V −1 , attractive values for harvesting applications with square-law rectifiers.

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2002

MRS Proceedings, 2013

Papers in the Appendix were published in electronic format as Volume 1534

Journal of Crystal Growth, 2007

GaAs layers were grown by MBE on (631)-oriented substrates under a variety of growth conditions. ... more GaAs layers were grown by MBE on (631)-oriented substrates under a variety of growth conditions. The structural properties of the samples were studied by atomic force microscopy and micro-Raman spectroscopy. Hillock structures were formed on the layers surface presenting an elongation towards the [5¯,9,3] direction, with dimensions and density that depend on the growth conditions. Raman spectra from the samples

Japanese Journal of Applied Physics, 1997

Reflection high-energy electron diffraction, atomic force microscopy, and Auger spectroscopy were... more Reflection high-energy electron diffraction, atomic force microscopy, and Auger spectroscopy were used to study the initial stages of growth of ZnSe on Si(111) substrates by molecular beam epitaxy. Initially, ZnSe grows in a three dimensional mode: after 7 monolayers (ML) of depositon the islands height is ∼20 Å, with a diameter of ∼650 Å, and a density of ∼20 islands per µ m2. Around ∼10 ML of deposition the growth changes to a two dimensional mode, and finally, a flat ZnSe surface is obtained for ∼30 ML. The island formation at the initial stage of growth could be used to synthesize self assembling ZnSe-quantum dots. On the other hand, the fast change to a two dimensional growth mode is very useful for structures requiring a flat surface.

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1999

Japanese Journal of Applied Physics, 1992

The electronic structure of n-Al0.28Ga0.72As/In0.23Ga0.77As/GaAs has been investigated by photolu... more The electronic structure of n-Al0.28Ga0.72As/In0.23Ga0.77As/GaAs has been investigated by photoluminescence (PL) and photoreflectance (PR) spectroscopies. Transitions associated with the n{=}1 and 2 electron subbands in the In0.23Ga0.77As single quantum well were observed. Two-dimensional carrier density was evaluated in terms of the quantum confined Franz-Keldysh (FK) effect of the transition between the lowest states of electrons and heavy holes. Because of penetrations of the confined electron density into the neighboring layers, PR spectra of GaAs show FK oscillation.

Novedosos tratamientos fueron realizados in-situ a superficies de GAAS (100) con el proposito de ... more Novedosos tratamientos fueron realizados in-situ a superficies de GAAS (100) con el proposito de obtener una mayor uniformidad en los tamanos de los puntos cuanticos (QDS) autoensamblados de InAs. Los tratamientos consistieron en exponer las superficies de GaAs a temperatura alta por 10 segundos con el obturador de As 4 cerrado. En un primer experimento la superficie de GaAs unicamente se mantuvo a 650°C sin ningun flujo, mientras que en el otro crecimiento el obturador de Si se abrio durante la interrupcion del flujo de Aa 4 . Ambos experimentos se compararon con una muestra crecida convencionalmente. Notables diferencias fueron observadas en la cinetica de crecimiento cuando el deposito de InAs se realizo sobre las diferentes superficies tratadas de GaAs. El tratamiento termico realizado sin flujo de Si extiende a mucho mayor espesor la transicion del crecimiento bidimensional a tridimensional de InAs. Por el contrario, la muestra tratada con Si mostro mas tempana relajacion de re...

Innovative Food Science & Emerging Technologies, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Japanese Journal of Applied Physics, 2018

The high order self-organization of quantum dots is demonstrated in the growth of InAs on a GaAs(... more The high order self-organization of quantum dots is demonstrated in the growth of InAs on a GaAs(631)-oriented crystallographic plane. The unidimensional ordering of the quantum dots (QDs) strongly depends on the As flux beam equivalent pressure (P As) and the cation/anion terminated surface, i.e., A-or B-type GaAs(631). The self-organization of QDs occurs for both surface types along ½ 113, while the QD shape and size distribution were found to be different for the self-assembly on the A-and B-type surfaces. In addition, the experiments showed that any misorientation from the (631) plane, which results from the buffer layer waviness, does not allow a high order of unidimensional arrangements of QDs. The optical properties were studied by photoluminescence spectroscopy, where good correspondence was obtained between the energy transitions and the size of the QDs.

Journal of Magnetism and Magnetic Materials, 2018

We report the influence of the Mn atomic concentration (at.%) on the nanostructures formation and... more We report the influence of the Mn atomic concentration (at.%) on the nanostructures formation and magnetic properties of GaAs:Mn layers grown by Molecular Beam Epitaxy at a relatively high substrate temperature of 530°C varying the nominal Mn at.% content from 0.01 to 0.2. It is shown that by modifying the Mn at.% different kind of nanostructures, ranging from 2D (such as islands and surface corrugation) to 3D microleaveand nanowire-like arrays, form on the surface layer. Samples produced with Mn contents ranging from 0.02 to 0.20 at.% show a significant room temperature ferromagnetic response that is attributed to the formation of MnAs nanocrystals as confirmed from X-ray diffraction analysis and magnetization measurements. The influence of MnAs clusters on the formation of the nanostructures observed is discussed.