Photoluminescence characterization of GaAs quantum well laser structure with AlAs/GaAs superlattices waveguide

Dependence on the excitation power and temperature of the photoluminescence emission of GaAs quantum well laser structures using GaAs/AlAs superlattices in the waveguide is reported. The effects related to a quality reduction due to the presence of a thick ternary AlGaAs cladding layer in the bottom of the laser structure were elucidated by comparing to the photoluminescence of a similar waveguide structure, except for the AlGaAs bottom layer. The excitation power dependence shows the strong excitonic origin of the light emission in the temperature range 4-300 K in both structures. Carrier transport mechanisms through the superlattices is analyzed from the evolution of the photoluminescence of the quantum well and the superlattice confining layers; a structure dependent transparency temperature is defined, at which transport changes from tunneling assisted to extended minibands regime. The value of this parameter depends on the localized states in the superlattice minibands, caused by interface roughness.Peer Reviewe

Folded acoustic phonons in InAs-AlAs strained-layer superlattices

Raman spectroscopy is used to characterize highly mismatched (7%) InAs-AlAs superlattices grown by atomic layer molecular beam epitaxy. In particular, folded acoustic modes are presented and compared with two different theoretical models (Rytov and linear chain). We find good agreement between theory and experiments. We estimate, with a simple model, the magnitude of the effect of the strain on the phonon frequency shifts.Peer Reviewe

Optical properties of GaAs/GaP strained-layer superlattices

The optical properties of a novel system, the GaAs/GaP strained-layer superlattice, are studied and compared with a theoretical model. Photoluminescence and photoreflectance measurements revealed that among the set of superlattices under study type-I and type-II behaviors (similar to those found in the lattice-matched GaAs/AlAs system) are present. The evolution of the photoluminescence peaks as a function of temperature and excitation density supported the assignment of the transitions involved. This is to our knowledge the first observation of direct (type-I) and indirect (type-II) transitions in strained-layer superlattices. A comparison with a theoretical model has led to an estimation of the conduction-band offset as 0.4 eV, which is the first value obtained from experiment in a GaAs/GaP heterojunction.Peer Reviewe

Raman scattering of InAs/AlAs strained-layer superlattices

We report on the resonance behavior around the E1 optical gap of the confined phonons of InAs/AlAs strained-layer superlattices. Near such a gap both types of phonons (A1,B2) resonate. We discuss their resonance and compare it with the behavior when exciting near the fundamental band-gap transition. © 1989 The American Physical Society.Peer Reviewe

Raman-scattering study of GaP/InP strained-layer superlattices

We discuss the first-order Raman spectra of short-period GaP/InP strained-layer superlattices grown by atomic-layer molecular-beam epitaxy on {001} GaAs substrates. Experimental spectra are successfully explained and compared to the results of simulations consisting of a linear-chain-method calculation combined with the bond-polarizability model. © 1992 The American Physical Society.Peer Reviewe

Confined optical phonons in GaAs/GaP strained layer superlattices

In this letter we report on Raman characterization of GaAs/GaP short period strained layer superlattices grown on GaAs (100) substrates by Atomic layer Molecular Beam Epitaxy (ALMBE). Confined optical phonons are observed in this highly strained system. The experimental results are compared with a calculation based on the equivalent wave-vector model. © 1989.Peer Reviewe

LOW-TEMPERATURE GROWTH OF AlAs/GaAs HETEROSTRUCTURES BY MODULATED MOLECULAR BEAM EPITAXY.

Modulated molecular beams phase-locked to reflection high-energy electron diffraction (RHEED) oscillations have been used to grow low-temperature GaAs quantum wells (QW) confined by AlAs/GaAs short-period superlattices (SL). Two different phase-locked modulation growth modes were attempted and compared. In the first mode, only the As//4 beam was interrupted periodically in-phase with the monolayer growth cycle. In the second one, both Ga (or Al) and As//4 incident beams were modulated synchronously with the monolayer growth cycle. In the second one, both Ga (or Al) and As//4 incident beams were modulated synchronously with the monolayer period. Both growth methods were seen to produce high-optical-quality QW and SL's layers at low-growth temperatures (T//s approximately equals 400 degree C).Peer Reviewe

Low-Temperature Growth of AlAs/GaAs Heterostructures by Modulated Molecular Beam Epitaxy

3 páginas.Modulated molecular beams phase-locked to reflection high-energy electron diffraction (RHEED) oscillations have been used to grow low-temperature GaAs quantum wells (QW) confined by AlAs/GaAs short-period superlattices (SL). Two different phase-locked modulation growth modes were attempted and compared. In the first mode, only the As4 beam was interrupted periodically in-phase with the monolayer growth cycle. In the second one, both Ga (or Al) and As4 incident beams were modulated synchronously with the monolayer period. Both growth methods were seen to produce high-optical-quality QW and SL's layers at low-growth temperatures (Ts≃400°C).Peer reviewe

Strain distribution and structural characterization of short period GaAsGaP strained superlattices by raman and X-Ray scattering

Raman scattering is used to study structural properties of strained-layer GaAsGaP short period superlattices grown on GaAs substrates. Different thicknesses of the constituent layers and also the effect of different types of buffer layers are studied. From the energy and width of the confined optical phonons observed, information about strain accomodation in the layers, strain relaxation and, in general, about structural quality is achieved. © 1990.Peer Reviewe

Electronic structure of strained-layer AlAs/InAs (001) superlattices

(001) superlattices containing 15 principal layers of AlAs and either one or two of InAs have been grown by atomic-layer molecular-beam epitaxy on undoped (001) GaAs substrates. The samples, between 0.1 and 0.3 m thick, have been studied by photoluminescence, electroreflectance, and piezoreflectance and monitored by phonon Raman-scattering spectroscopy and x-ray diffractometry. An empirical tight-binding model, combined with surface Green-function matching, is used to discuss the experimental data. An overall picture is obtained for the electronic structure of these superlattices with a valence-band offset close to 0.5 eV, which is consistent with the observed spectra. © 1991 The American Physical Society.This work was partly supported by the Spanish Comision Interministerial de Ciencia y Tecnologia under Grant No. MAT88-0547. One of the authors, J. Arriaga, is indebted to Consejo Nacional de Ciencia y Tecnologia (CONACYT) (Mexico) for supportPeer Reviewe