Aperiodic Superlattices Research Articles

Effect of Spatially Correlated Disorder on Electronic Transport Properties of Aperiodic Superlattices (GaAs/AlxGa1-xAs)

Effect of Spatially Correlated Disorder on Electronic Transport Properties of Aperiodic Superlattices (GaAs/AlxGa1-xAs)

Structural parameters and their effects on the electronic transport properties in aperiodic superlattice profile

The aperiodic GaAs/AlxGa1−xAs superlattices (SL) with trimer disorder have been studied in this paper. The transfer-matrix technique and the exact Airy function formalism have been used to determine the miniband structure, the transmission coefficient, the resonance energy and resonant tunneling time (RTT). Although the disorder localizes the states on average, our numerical calculations show that the localization length of the states becomes more extended when the disorder is correlated (trimer case). We have also found that the RTT is of the order of several femtoseconds.

Energy band and transport properties in magnetic aperiodic graphene superlattices of Thue-Morse sequence

Utilizing the transfer matrix method, we develop the electronic band structure and transport properties in Thue-Morse aperiodic graphene superlattices with magnetic barriers. It is found that the normal transmission is blocked and the position of the Dirac point can be shifted along the wavevector axis by changing the height and width ratio of magnetic barriers, which is intrinsic different from electronic field modulated superlattices. In addition, the angular threshold property of the transmission spectra and the oscillatory property of the conductance have been studied.

Effects of Aperiodicity and Roughness on Coherent Heat Conduction in Superlattices

Coherent phonon heat conduction has recently been confirmed experimentally in superlattice structures. Such traveling coherent phonon waves in superlattices lead to a linear increase in thermal conductivity as the number of periods increases. For applications such as thermal insulation or thermoelectrics, minimization of the phonon coherent effect is desirable. In this work, we use molecular dynamics simulations to study how to control coherent heat conduction in superlattices (SLs). It is found that either aperiodic SLs or SLs with rough interfaces can significantly disrupt coherent heat conduction when the interface densities are high. For sample thickness less than 125 nm, aperiodic SLs with perfect interfaces are found to have the lowest thermal conductivity. We use the atomic Green’s function method to examine the phonon dynamics. The impact of either aperiodicity or interface roughness is attributed to reduced transmittance. Such impact diminishes as the interface density reduces.

Future directions in standing-wave photoemission

Over the past decade, standing-wave photoemission (SW-XPS) has evolved into a powerful and versatile non-destructive technique for probing element-specific electronic, magnetic, and structural properties of buried layers and interfaces with sub-nanometer depth resolution. In this article, I will discuss several promising future directions in this emergent field stemming from experimental and theoretical studies wherein SW-XPS is combined with other X-ray techniques, such as magnetic circular dichroism (MCD), hard X-ray photoemission spectroscopy (HAXPES), angle-resolved photoemission (ARPES), and photoemission microscopy (PEEM), adding extra dimensions to the measurement and thus widening the scope of scientific and technological questions accessible via the use of standing waves. I will further discuss examples of recently developed methods for X-ray standing-wave data analysis, which yield layer-resolved matrix-element-weighted densities of states at interfaces as well as Ångstrom-level changes in periodicity of synthetic superlattices. Finally, I will explore the possibility of localizing the standing waves near the surface and within a buried layer by the use of aperiodic superlattices, total reflection, and X-ray waveguide effects.

Multifractal analysis of the electronic states in the Fibonacci superlattice under weak electric fields

Influence of the weak electric field on the electronic structure of the Fibonacci superlattice is considered. The electric field produces a nonlinear dynamics of the energy spectrum of the aperiodic superlattice. Mechanism of the nonlinearity is explained in terms of energy levels anticrossings. The multifractal formalism is applied to investigate the effect of weak electric field on the statistical properties of electronic eigenfunctions. It is shown that the applied electric field does not remove the multifractal character of the electronic eigenfunctions, and that the singularity spectrum remains non-parabolic, however with a modified shape. Changes of the distances between energy levels of neighbouring eigenstates lead to the changes of the inverse participation ratio of the corresponding eigenfunctions in the weak electric field. It is demonstrated, that the local minima of the inverse participation ratio in the vicinity of the anticrossings correspond to discontinuity of the first derivative of the difference between marginal values of the singularity strength. Analysis of the generalized dimension as a function of the electric field shows that the electric field correlates spatial fluctuations of the neighbouring electronic eigenfunction amplitudes in the vicinity of anticrossings, and the nonlinear character of the scaling exponent confirms multifractality of the corresponding electronic eigenfunctions.

Transparent-Component-Decimation Method for Studying the Optical Transmission of One Kind of Aperiodic Superlattices

Transparent-component-decimation (TCD) method may simplify the aperiodic sequences to the simplest form and one can obtain the transmissive characteristics without complicated calculations. Applying this method to the Family A of Generalized Thue-Morse [FAGTM(n)] aperiodic superlattices, we obtain directly the formulas of the transmission coefficients at the central wavelength. The results are in accord with the previous published results. It shows that the TCD method can be used to study optical transmission normally through aperiodic multilayers directly and exactly and has bright future.

Quasicrystalline order in self-assembled binary nanoparticle superlattices

The discovery of quasicrystals in 1984 changed our view of ordered solids as periodic structures and introduced new long-range-ordered phases lacking any translational symmetry. Quasicrystals permit symmetry operations forbidden in classical crystallography, for example five-, eight-, ten- and 12-fold rotations, yet have sharp diffraction peaks. Intermetallic compounds have been observed to form both metastable and energetically stabilized quasicrystals; quasicrystalline order has also been reported for the tantalum telluride phase with an approximate Ta(1.6)Te composition. Later, quasicrystals were discovered in soft matter, namely supramolecular structures of organic dendrimers and tri-block copolymers, and micrometre-sized colloidal spheres have been arranged into quasicrystalline arrays by using intense laser beams that create quasi-periodic optical standing-wave patterns. Here we show that colloidal inorganic nanoparticles can self-assemble into binary aperiodic superlattices. We observe formation of assemblies with dodecagonal quasicrystalline order in different binary nanoparticle systems: 13.4-nm Fe(2)O(3) and 5-nm Au nanocrystals, 12.6-nm Fe(3)O(4) and 4.7-nm Au nanocrystals, and 9-nm PbS and 3-nm Pd nanocrystals. Such compositional flexibility indicates that the formation of quasicrystalline nanoparticle assemblies does not require a unique combination of interparticle interactions, but is a general sphere-packing phenomenon governed by the entropy and simple interparticle potentials. We also find that dodecagonal quasicrystalline superlattices can form low-defect interfaces with ordinary crystalline binary superlattices, using fragments of (3(3).4(2)) Archimedean tiling as the 'wetting layer' between the periodic and aperiodic phases.

Photonic Band Structure of Fibonacci Superlattices with Metamaterials. Part 1: The Algebraic Method of Calculation for Lossless Layers

We study the properties of the photonic band structure (PBS) of infinite and binary Fibonacci superlattices (FS) containing metamaterial lossless layers. The transfer matrix method (TMM) and periodic boundary conditions are applied. The algebraic method of PBS calculations, based on the Bloch theorem, is described and used. The dispersion relations, for both type of light polarization, characterizing peculiarities of PBS are calculated numerically and presented. Fractal properties of a photonic band structure and the existence of so called zero-n gaps are established. Full Text: PDF References E. Macia,"The role of aperiodic order in science and technology", Rep. Prog. Phys. 69, 397 (2006) [CrossRef] W. Steurer, D. Suter-Widmer,"Photonic and phononic quasicrystals", J. Phys. D: Appl. Phys. 40, R229 (2007) [CrossRef] S. A. Ramakrishna, T. M. Grzegorczyk, "Physics and Applications of Negative Refractive Index Materials", SPIE Press and CRC Press 2009 J.E. Lugo et al,"Multiband negative refraction in one-dimensional photonic crystals", Optics Express, 17, 3042 (2009) [CrossRef] H. Zhang, X. Chen, Y. Li, Y. Fu, N. Yuan,"The Bragg gap vanishing phenomena in one-dimensional photonic crystals", Optics Express, 17, 7800 (2009) [CrossRef] M. de Dios-Leyva, J.C. Drake-Perez,"Zero-width band gap associated with the nŻ =0 condition in photonic crystals containing left-handed materials", Phys. Rev. E, 79, 036608 (2009) [CrossRef] M. de Dios-Leyva, O.E. Gonzales-Vasquez,"Band structure and associated electromagnetic fields in one-dimensional photonic crystals with left-handed materials", Phys. Rev. B, 77,125102 (2008) [CrossRef] R. Srivastava, K.B. Thapa, S. Pati, S.P. Ojha,"Negative refraction in 1D photonic crystals", Sol. State Comm., 147, 157 (2008) [CrossRef] Y. Fang, S. He,"Transparent structure consisting of metamaterial layers and matching layers", Phys. Rev. A, 78, 023813 (2008) [CrossRef] A. Bruno-Alfonso, E. Reyes-Gomez, S.B. Cavalcanti, L.E. Oliveira,"Band edge states of the ?n?=0 gap of Fibonacci photonic lattices", Phys. Rev. A, 78, 035801 (2008) [CrossRef] Eds. C. M. Krowne, Y. Zhang, "Physics of Negative Refraction and Negative Index Materials", Springer 2007 Y.-T Fang, J. Zhou, E.Y.B. Pun,"High-Q filters based on one-dimensional photonic crystals using epsilon-negative materials", Appl. Phys. B, 86, 587 (2007) [CrossRef] X. Hu, Z. Liu, Q. Gong,"A multichannel filter in a photonic crystal heterostructure containing single-negative materials", J. Opt. A: Pure Appl. Opt., 9, 877 (2007) [CrossRef] F. F. de Medeiros, E. L. Albuquerque, M. S. Vasconcelos,"Transmission spectra in photonic band-gap Fibonacci nanostructures", Surface Science, 601, 4492 (2007) [CrossRef] K. Tarnowski, W. Salejda, M. H. Tyc,"Propagation of polarized light through optical nanosuperlattices", Optica Applicata, 37, 387, 2007 M.H. Tyc, W. Salejda, A. Klauzer-Kruszyna, K. Tarnowski,"Photonic band structure of one-dimensional aperiodic superlattices composed of negative refraction metamaterials", SPIE Proceedings Series, 2007, 6581, 658112 [CrossRef] M.H. Tyc, W. Salejda, A. Klauzer-Kruszyna, K. Tarnowski,"Propagation of polarized light through superlattices composed of left- and right-handed materials", SPIE Proceedings Series, 2007, 6581, 658113 [CrossRef] P. Yeh, "Optical Waves in Layered Media", Wiley-Interscience 2005 H.X. Da, C. Xu, Z.Y. Li,"Omnidirectional reflection from one-dimensional quasi-periodic photonic crystal containing left-handed material", Phys. Lett. A, 345, 459 (2005) [CrossRef] W. Salejda, A. Klauzer-Kruszyna, M. H. Tyc, K. Tarnowski,"One-dimensional photonic quasicrystals: application to Bragg reflectors", SPIE Proceedings Series, 2005, 5950, 59501Q [CrossRef] W. Salejda, A. Klauzer-Kruszyna, M. H. Tyc, K. Tarnowski,"Electromagnetic wave propagation through aperiodic superlattices composed of left- and right-handed materials", SPIE Proceedings Series, 2005, 5955, 595514 [CrossRef] J. Li, D. Zhao, Z. Liu,"Zero n - photonic band gap in a quasiperiodic stacking of positive and negative refractive index materials", Phys. Lett. A, 332, 461 (2004) [CrossRef] A. Klauzer- Kruszyna, W. Salejda, M.H. Tyc,"Polarized Light Transmission through Generalized Fibonacci Multilayers. I. Dynamical maps approach", Optik, 115, 257 (2004) A. Klauzer- Kruszyna, W. Salejda, M.H. Tyc,"Polarized Light Transmission through Generalized Fibonacci Multilayers. II. Numerical Results", Optik, 115, 267 (2004) M. Kohomoto, B. Sutherland, K. Iguchi,"Localization of optics: Quasiperiodic media", Phys. Rev. Lett., 58, 2436 (1987) [CrossRef] J. Li, L. Zhou, C.T. Chan, P. Shang,"Photonic Band Gap from a Stack of Positive and Negative Index Materials", Phys. Rev. Lett., 90, 083901 (2003) [CrossRef]

Optical transmission through generalized Thue-Morse superlattices

Abstract In this paper we study the transmission properties of light through generalized Thue-Morse (GTM (m, n)) aperiodic superlattices and obtain the formulae of the transmission coefficients (TCs) analytically at the central wavelength, which are confirmed by numerical simulations. It is found that: (1) all of the 1st generation systems are transparent to the substrates medium B; (2) GTM (m, 2 j) systems are transparent to the substrates medium B; (3) GTM (2i, 2j + 1) systems are translucent to the substrates medium B except the 1st generation; and (4) when i not equal j, transmission through GTM (2i + 1, 2j + 1) systems attenuates rapidly with the increase of generation number l and sequence parameters m, n. On the other hand, the positional correlations between the constituents of GTM (m, n) aperiodic superlattices responsible for the resonant states are also discussed. Based on the conclusions we study the properties of the amplitude of the electric field vector and find that they are different from those of periodic lattices and chaotic systems.

Optical transmission through generalized SML superlattices

The SML model is a kind of one-dimensional (1D) quasiperiodic three-tilestructure proposed by Liu et al (1991 Phys. Rev. B 43 13240; 1991 Chin. Phys. Lett.8 533) based on the experimental results of Al–Si–Mn quasicrystals (Boissieuet al 1990 J. Phys.: Condens. Matter 2 2499). Generalized SML models(GSML(m,n)) are extensions of the SML one. In this paper, we study the transmission properties of light throughGSML(m,n) aperiodic superlattices and use the transparent-component-decimation (TCD) method toanalyze the relationship between the characteristics of structures and transmission coefficients.It is found that the propagation matrices (PMs) and transmission coefficients (TCs) forGSML(m,n) multilayers exhibit interesting properties: (1) whenn is even, they are allconstant; (2) when n is odd but m is even, the former exhibit a six-cycle property while the latter possess a three-cycle feature; (3) whenn is oddand m = 1, they both possess a pseudo-seven-cycle characteristic. The analytic results are confirmedby numerical evaluations.

Transparent-component-decimation method for studying the optical transmission of binary aperiodic superlattices

In this paper we propose the transparent-component-decimation (TCD) method to study the optical transmission normally through aperiodic superlattices. Comparing with the conventional trace and antitrace-map technique, the TCD method may simplify the aperiodic sequences to the simplest form and one can obtain the transmissive characteristics without complicated calculations. Applying this method to two kinds of binary aperiodic superlattices, we obtain directly the formulas of the transmission coefficients (TCs) at the central wavelength. The results are in accord with previously published results. It shows that the TCD method is powerful for the investigation of optical transmission through aperiodic multilayers.

Structural Relationships between QC and Meta-stable Crystalline Phases in Melt Spun Zr80Pt20 Ribbons

ABSTRACTTwo competing meta-stable crystalline phases, a bcc hyperstoichiometric β-Zr(Pt) (Im3m) superstructure and a non-stoichiometric fcc ε-Zr6Pt3O (Fd3m) phase, have been observed to coexist with a quasicrystalline (i) phase, respectively, in as-spun Zr80Pt20 ribbons with low oxygen content (184ppm mass O) and high oxygen content (4737 ppm mass O). Transmission electron microscopy (TEM) results show that the β-Zr(Pt) superstructure and i phase have a well defined orientational relationship, good crystallographic match and nearly identical stoichiometry. Icosahedral two-fold axes coincide with <110>, <111>, <112> and <113> axes in β-Zr(Pt); {110}β-Zr planes register with icosahedral {211111} fivefold or {221001} twofold planes. The observed orientational relationship and the space group (Im3m) preclude β-Zr(Pt) as a cubic approximant to the i phase. Both β-Zr(Pt) and the i phase are distorted; β-Zr(Pt) maintains a basic β-Zr Bravais lattice with an aperiodic superlattice. Morphologies suggest that the i phase forms first, followed by an easy nucleation of the β-Zr(Pt) on the surfaces of the i phase. Also, a similar orientational relationship and lattice match between ε-Zr6Pt3O and i phase has been revealed by TEM.

Localization-delocalization in aperiodic systems

Spectral and dynamical properties of electrons, phonons, electromagnetic waves, and nonlinear coherent excitations in one-dimensional modulated structures with long-range correlations are investigated from a theoretical point of view. First a proof of singular continuous electron spectrum for the tight-binding Schrodinger equation with an on-site potential, which, in analogy with a random potential, has an absolutely continuous correlation measure, is given. The critical behavior of such a localization phenomenon manifests in anomalous diffusion for the time-evolution of electronic wave packets. Spectral characterization of elastic vibrations in aperiodically ordered diatomic chains in the harmonic approximation is achieved through a dynamical system induced by the trace maps of renormalized transfer matrices. These results suggest that the zero Lebesgue measure Cantor-set spectrum (without eigenvalues) of the Fibonacci model for a quasicrystal is generic for deterministic aperiodic superlattices, for which the modulations take values via substitution rules on finite sets, independent of the correlation measure. Secondly, a method to synthesize and analyze discrete systems with prescribed long-range correlated disorder based on the conditional probability function of an additive Markov chain is effectively implemented. Complex gratings (artificial solids) that simultaneously display given characteristics of quasiperiodic crystals and amorphous solids on the Fraunhofer diffraction are designated. A mobility edge within second order perturbation theory of the tight-binding Schrodinger equation with a correlated disorder in the dichotomic potential realizes the success of the method in designing window filters with specific spectral components. The phenomenon of self-localization in lattice dynamical systems is a subject of interest in various physical disciplines. Lattice solitons are studied using the discrete nonlinear Schrodinger equation with on-site potential, modeling coherent structures in, for example, photonic crystals. The instability-induced dynamics of the localized gap soliton is found to thermalize according to the Gibbsian equilibrium distribution, while the spontaneous formation of persisting intrinsic localized modes from the extended out-gap soliton reveals a phase transition of the solution.

Anomalous transmission of phonons in superlattices at oblique propagation: an analysis based on finite difference equations

Anomalous mode-converted transmission of phonons is studied based on the new formulas for the transmitted amplitudes of phonons propagating oblique to the layer interfaces of superlattices. A transfer matrix which well describes the transmission of the coupled longitudinal and transverse phonons in an isotropic model is introduced. With the use of this transfer matrix we can derive finite difference equations which govern the transmitted amplitudes of both the longitudinal and transverse phonons. These equations can be solved exactly for periodic superlattices and approximately for certain aperiodic superlattices. The results are applied to the study of the unusual intermode oscillations in phonon transmission in both periodic superlattices and aperiodic superlattices with variable thickness of bilayers.

Optical properties of quasiperiodic and aperiodic PbS-CdS superlattices

The transmission spectra of quasiperiodic Fibonacci superlattices and aperiodic Thue-Morse superlattices of the system PbS-CdS at room temperature and at 77 K are investigated. The superlattices are fabricated by pulsed laser-beam evaporation. The spectrum of optical transitions of the aperiodic superlattice is much richer than implied by a calculation of the spectrum of periodic superlattices. This is a consequence of the fractal structure of the energy spectrum of the aperiodic superlattices. Self-similarity is observed in the energy spectra of Thue-Morse lattices.

Bloch oscillations

Restricted accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Kurz Heinrich , Roskos Hartmut G. , Dekorsy Thomas and Klaus Köhler 1996Bloch oscillationsPhil. Trans. R. Soc. A.3542295–2310http://doi.org/10.1098/rsta.1996.0101SectionRestricted accessArticleBloch oscillations Heinrich Kurz Google Scholar Find this author on PubMed Search for more papers by this author , Hartmut G. Roskos Google Scholar Find this author on PubMed Search for more papers by this author , Thomas Dekorsy Google Scholar Find this author on PubMed Search for more papers by this author and Köhler Klaus Google Scholar Find this author on PubMed Search for more papers by this author Heinrich Kurz Google Scholar Find this author on PubMed Search for more papers by this author , Hartmut G. Roskos Google Scholar Find this author on PubMed Search for more papers by this author , Thomas Dekorsy Google Scholar Find this author on PubMed Search for more papers by this author and Köhler Klaus Google Scholar Find this author on PubMed Search for more papers by this author Published:15 October 1996https://doi.org/10.1098/rsta.1996.0101AbstractThe status quo of the research on Bloch oscillations in semiconductor superlattices is outlined. Bloch oscillations excited by femtosecond laser pulses have been investigated by different optical techniques. They have allowed measurement of the internal electric field changes associated with the charge oscillations, the emitted terahertz electromagnetic radiation and the nonlinear coherent optical response, all directly in the time domain. The main results are summarized and critically reviewed. The potential of Bloch oscillations for practical applications in terahertz radiation sources is assessed.FootnotesThis text was harvested from a scanned image of the original document using optical character recognition (OCR) software. As such, it may contain errors. Please contact the Royal Society if you find an error you would like to see corrected. Mathematical notations produced through Infty OCR. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by Islam Q, Meng F, Thomson M and Roskos H (2020) Terahertz photoconductive waveguide emitter with excitation by a tilted optical pulse front, Optics Express, 10.1364/OE.403161, 28:22, (33673), Online publication date: 26-Oct-2020. Gruzdev V and Sergaeva O (2018) Ultrafast modification of band structure of wide-band-gap solids by ultrashort pulses of laser-driven electron oscillations, Physical Review B, 10.1103/PhysRevB.98.115202, 98:11 Vakhnenko O (2016) Coupling-governed metamorphoses of the integrable nonlinear Schrödinger system on a triangular-lattice ribbon, Physics Letters A, 10.1016/j.physleta.2016.04.034, 380:24, (2069-2074), Online publication date: 1-May-2016. Muniz C and Cunha M (2015) Effects of strong electric fields in a polyacetylene chain, Journal of Physics and Chemistry of Solids, 10.1016/j.jpcs.2015.02.009, 82, (17-20), Online publication date: 1-Jul-2015. Sokolov V and Iafrate G (2012) Spontaneous Emission of Bloch Oscillation Radiation in the Terahertz Regime Handbook of Nanoscience, Engineering, and Technology, Third Edition, 10.1201/b11930-9, (67-124), Online publication date: 15-Jun-2012. Belotelov V, Bykov D, Doskolovich L and Zvezdin A (2010) On surface plasmon polariton wavepacket dynamics in metal–dielectric heterostructures, Journal of Physics: Condensed Matter, 10.1088/0953-8984/22/39/395301, 22:39, (395301), Online publication date: 6-Oct-2010. Hummel A, Bauer T, Mohler E and Roskos H (2006) The coherent Hall effect of charge carriers in a superlattice: semiclassical description of the wavepacket dynamics, Journal of Physics: Condensed Matter, 10.1088/0953-8984/18/8/013, 18:8, (2487-2509), Online publication date: 1-Mar-2006. Axt V and Kuhn T (2004) Femtosecond spectroscopy in semiconductors: a key to coherences, correlations and quantum kinetics, Reports on Progress in Physics, 10.1088/0034-4885/67/4/R01, 67:4, (433-512), Online publication date: 1-Apr-2004. Gaidis M, Lee K, Samoska L and Wyss R Frequency-controlled sources of far-infrared radiation for spaceborne applications 2000 IEEE/EIA International Frequency Control Symposium and Exhibition, 10.1109/FREQ.2000.887419, 0-7803-5838-4, (565-577) Kempa K, Bakshi P, Du C, Feng G, Scorupsky A, Strasser G, Rauch C, Unterrainer K and Gornik E (1999) Towards stimulated generation of coherent plasmons in nanostructures, Journal of Applied Physics, 10.1063/1.369736, 85:7, (3708-3712), Online publication date: 1-Apr-1999. Wolter F, Martini R, Tolk S, Haring Bolivar P, Kurz H, Hey R and Grahn H (1999) Influence of carrier–carrier scattering on intraband dephasing, Superlattices and Microstructures, 10.1006/spmi.1999.0763, 26:2, (93-102), Online publication date: 1-Aug-1999. Shah J (1999) Recent Developments Ultrafast Spectroscopy of Semiconductors and Semiconductor Nanostructures, 10.1007/978-3-662-03770-6_9, (325-446), . Luban M and Luscombe J (1998) Dynamical localization of electrons in an aperiodic superlattice, Physical Review B, 10.1103/PhysRevB.57.9043, 57:15, (9043-9049) Chamberlain J, Miles R, Collins C and Steenson D (1997) Introduction to Terahertz Solid-State Devices New Directions in Terahertz Technology, 10.1007/978-94-011-5760-5_1, (3-27), . Cho G, Ziebell A, Dekorsy T, Bakker H, Opitz U, Kohl A and Kurz H (1997) Electroabsorption Dynamics in an InGaAsP/InGaAsP Superlattice Modulator Ultrafast Electronics and Optoelectronics, 10.1364/UEO.1997.UG5, 1-55752-486-6, (UG5) This Issue15 October 1996Volume 354Issue 1717 Article InformationDOI:https://doi.org/10.1098/rsta.1996.0101Published by:Royal SocietyPrint ISSN:1364-503XOnline ISSN:1471-2962History: Published online01/01/1997Published in print15/10/1996 License:Scanned images copyright © 2017, Royal Society Citations and impact

Characterization of Al 0.4Ga 0.6As/GaAs aperiodic superlattices by photoluminescence spectroscopy at 2 K

We present photoluminescence excitation (PLE) and picosecond time-resolved photoluminescence (TRPL) results of an aperiodic superlattice (ASL) in static electric fields applied perpendicular to the heterojunction interfaces. The ASL consists of nine GaAs quantum wells separated by Al 0.4Ga 0.6As barriers of varying thickness, such that electronic states in individual QWs are in resonance in a finite electric field (∼45 kV cm 1). We observed a drastic quenching of the photoluminescence intensity when the field is increased over a critical value, and a triple resonance of the heavy-hole exciton states originally confined in neighboring QWs, confirming the formation of an electron quasi-miniband. The TRPL and PLE spectra also suggest that the Coulomb-interaction-induced redistribution of exciton oscillator strength is strongly field-dependent at the resonant field. The ASL structure is demonstrated to achieve control of both optical and transport properties in desired electric fields. Theoretical calculations emphasis on the electron state resonance and the exciton radiative lifetime are performed to understand the experimental data.

Can fractal-like spectra be experimentally observed in aperiodic superlattices?

We numerically investigate the effects of inhomogeneities in the energy spectrum of aperiodic semiconductor superlattices, focusing our attention on Thue-Morse and Fibonacci sequences. In the absence of disorder, the corresponding electronic spectra are self-similar. The presence of a certain degree of randomness, due to imperfections occurring during the growth processes, gives rise to a progressive loss of quantum coherence, smearing out the finer details of the energy spectra predicted for perfect aperiodic superlattices and spurring the onset of electron localization. However, depending on the degree of disorder introduced, a critical size for the system exists, below which peculiar transport properties, related to the pre-fractal nature of the energy spectrum, may be measured.

InAlP/InGaP strain-modulated aperiodic superlattice heterobarrier for enhanced electron confinement in visible (λ∼650 nm) light-emitting devices

We report the design, growth, and characterization of an InAlP/InGaP strain-modulated aperiodic superlattice heterobarrier (SMASH) for the enhancement of the performance of visible light-emitting devices. These InAlP/InGaP heterostructures are grown on GaAs substrates by low-pressure metalorganic chemical vapor deposition. Electron-wave reflectivity calculations show that the virtual confining potential energy for conduction-band electrons at the InAlP/InGaP interface can be increased by up to ∼660 meV by employing this novel barrier. Significant improvements in photoluminescence intensity at 300 and 4.2 K are observed from both InGaP quantum well and InGaP bulk-layer double heterostructures utilizing the SMASH structure.