B. Jusserand

Confinement of acoustical vibrations in a semiconductor planar phonon cavity.

Extending the idea of optical microcavities to sound waves, we propose a phonon cavity consisting of two semiconductor superlattices enclosing a spacer layer. We show that acoustical phonons can be confined in such layered structures when the spacer thickness is an integer multiple of the acoustic half-wavelength at the center of one of the superlattice folded minigaps. We report Raman scattering experiments that, taking profit of an optical microcavity geometry, demonstrate unambiguously the observation of a phonon-cavity confined acoustical vibration in a GaAs/AlAs based structure. The experimental results compare precisely with photoelastic model calculations of the Raman spectra.

Raman scattering characterization of interface broadening in GaAs/AlAs short period superlattices grown by molecular beam epitaxy

We analyze in this letter the Raman scattering spectra on several GaAs/AlAs short period superlattices grown by molecular beam epitaxy with different substrate temperatures and different doping concentrations. The frequency and Raman intensity of both folded acoustical and confined optical phonons, which are observed in all samples, are clearly related to the substrate temperature. These variations: (i) decreasing intensity of the folded acoustical modes, (ii) frequency shift of the optical modes confined in GaAs, are successfully analyzed in terms of interface broadening. A quantitative estimation of the interface widths is obtained and analyzed.

Atomic‐scale roughness of GaAs/AlAs interfaces: A Raman scattering study of asymmetrical short‐period superlattices

We present Raman spectra obtained from very short period (a few atomic layers) GaAs/AlAs superlattices with asymmetrical unit cells containing two different GaAs wells. This allows us to analyze quantitatively for the first time the atomic‐scale component of the interface roughness. We demonstrate that it mainly originates at the GaAs on AlAs interface and strongly decreases with the growth temperature and the underlying AlAs layer thickness.

Structural and optical properties of high quality InAs/GaAs short-period superlattices grown by migration-enhanced epitaxy

InAs/GaAs highly strained short‐period superlattices have been grown by migration‐enhanced epitaxy on InP(001) substrates. Such samples exhibit clearly improved structural and optical properties. X‐ray diffraction, scanning transmission electron microscopy, photoluminescence, and Raman scattering experiments have been performed to characterize an (InAs)4(GaAs)3 layer.

Optical cavity enhancement of light–sound interaction in acoustic phonon cavities

We describe a device that has a resonant cavity for acoustic phonons embedded inside an optical cavity. This double cavity structure is a resonator for acoustical phonons and enhances the interaction between sound and light. We discuss the design and material parameters relevant for the optimization of the acoustic phonon cavities, and we present Raman scattering experiments on GaAs/AlAs structures designed to confine from one to three acoustical phonon modes. We quantitatively study the amplification of the photon–phonon interaction in these devices reporting an enhancement factor of more than five orders of magnitude.

Coherent generation of acoustic phonons in an optical microcavity.

Ultrafast coherent generation of acoustic phonons is studied in a semiconductor optical microcavity. The confinement of the light pulse amplifies both the generation and the detection of phonons. In addition, the standing wave character of the photon field modifies the generation and detection phonon bandwidth. Coherent generation experiments in an acoustic nanocavity embedded in an optical microcavity are reported as a function of laser energy and incidence angle to evidence the separate role of the optical and exciton resonances. Amplified signals and phonon spectra modified by the optical confinement are demonstrated.

Long range gallium segregation in the AlAs layers of GaAs/AlAs superlattices

We demonstrate from Raman scattering on the AlAs‐type optical vibrations in GaAs/AlAs superlattices that small but significant amount of gallium atoms segregate in the AlAs layers over more than 10 monolayers from the AlAs on GaAs interface. We discuss the growth temperature dependence of this effect and its consequences for a global description of the interface roughness in this system.

Subterahertz monochromatic acoustic wave propagation using semiconductor superlattices as transducers

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Sub-Terahertz Monochromatic Transduction with Semiconductor Acoustic Nanodevices Agnès Huynh, Bernard Perrin, N. D. Lanzillotti Kimura, Bernard Jusserand, A. Fainstein, Aristide Lemaitre

Conduction band structure in wurtzite GaAs nanowires: A resonant Raman scattering study

We report on a room temperature Raman resonance at 1.56 eV in GaAs wurtzite nanowires together with the emergence of a strong forbidden longitudinal optical phonon line. We attribute this resonance, absent in zinc blende wires with similar diameters, to an additional excitonic transition due to conduction band folding in agreement with recent theoretical predictions.

Phonon Bloch oscillations in acoustic-cavity structures

We describe a semiconductor multilayer structure based in acoustic-phonon cavities and achievable with molecular beam epitaxy technology, designed to display acoustic-phonon Bloch oscillations. We show that forward and backscattering Raman spectra give a direct measure of the created phononic Wannier-Stark ladder. We also discuss the use of femtosecond laser impulsions for the generation and direct probe of the induced phonon Bloch oscillations. We propose a gedanken experiment based in an integrated phonon source-structure-detector device, and we present calculations of pump and probe time-dependent optical reflectivity that evidence temporal beatings in agreement with the Wannier-Stark ladder energy splitting.