Mathieu Perrin

Room temperature operation of GaAsP(N)/GaP(N) quantum well based light-emitting diodes: Effect of the incorporation of nitrogen

This letter deals with the electroluminescence emission at room temperature of two light-emitting diodes on GaP substrate, based on ternary GaAsP/GaP and quaternary GaAsPN/GaPN multiple quantum wells. In agreement with tight-binding calculations, an indirect band gap is demonstrated from the temperature-dependent photoluminescence for the first structure. High efficiency photoluminescence is then observed for the second structure. Strong electroluminescence and photocurrent are measured from the diode structures at room temperature at wavelengths of 660 nm (GaAsP/GaP) and 730 nm (GaAsPN/GaPN). The role of the incorporation of nitrogen on the optical band gap and on the nature of interband transitions is discussed.

Structural and optical analyses of GaP/Si and (GaAsPN/GaPN)/GaP/Si nanolayers for integrated photonics on silicon

We report a structural study of molecular beam epitaxy-grown lattice-matched GaP/Si(0 0 1) thin layers with an emphasis on the interfacial structural properties, and optical studies of GaAsP(N)/GaP(N) quantum wells coherently grown onto the GaP/Si pseudo substrates, through a complementary set of characterization tools. Room temperature photoluminescence at 780 nm from the (GaAsPN/GaPN) quantum wells grown onto a silicon substrate is reported. Despite this good property, the time-resolved photoluminescence measurements demonstrate a clear influence of non-radiative defects initiated at the GaP/Si interface. It is shown from simulations, how x-ray diffraction can be used efficiently for analysis of antiphase domains. Then, qualitative and quantitative analyses of antiphase domains, micro-twins, and stacking faults are reported using complementarity of the local transmission electron microscopy and the statistical x-ray diffraction approaches.

Evaluation of InGaPN and GaAsPN materials lattice-matched to Si for multi-junction solar cells

We compare the potentiality of bulk InGaPN and GaAsPN materials quasi-lattice-matched to silicon (Si), for multi-junction solar cells application. Bandgaps of both bulk alloys are first studied by a tight-binding model modified for nitrogen incorporation in diluted regimes. The critical thicknesses of those alloys are then calculated for various compositions. For the same lattice-mismatch and nitrogen amount, the bandgap of bulk GaAsPN is found to be closer to the targeted gap value of 1.7 eV for high efficiency tandem solar cell. GaPN and GaAsPN epilayers are then grown by molecular beam epitaxy on GaP substrate and studied by photoluminescence and X-ray diffraction. A GaAsPN bulk alloy emitting light at 1.77 eV at room temperature is obtained, demonstrating promising properties for further use in III-V/Si photovoltaic multijunction solar cells.

Atomistic calculations of Ga(NAsP)/GaP(N) quantum wells on silicon substrate: Band structure and optical gain

Band structure calculations of strained Ga(NAsP) quantum wells are performed within the framework of the extended-basis sp3d5s* tight-binding model. The nitrogen contribution is taken into account by introducing an additional sN orbital into the tight-binding basis. Biaxial strain effects on the band alignment of bulk Ga(NAsP) is studied for the ultra-diluted regime. We demonstrate a good agreement with experimental data both for transition energies and optical gain in Ga(NAsP) quantum wells. The effect of N incorporation in the laser active areas is simulated.

Room temperature photoluminescence of high density (In,Ga)As/GaP quantum dots

We report on the achievement of high density (In,Ga)As self-assembled quantum dots on GaP substrate with a good homogeneity. Good structural and electronic properties have been achieved, as revealed by room temperature photoluminescence measurements and by comparison to both InAs/GaAs and InAs/InP materials reference systems. This is supported by atomistic calculations where the indium incorporation in InGaAs/GaP quantum structures is found to enhance both the type-I bandlineup and direct bandgap properties. The photoluminescence temperature dependence of the bandgap evidences the quantum confinement effects. Our results provide a valid framework to implement silicon optical devices based on InGaAs/GaP nanostructures.

Carrier recombination dynamics in In x Ga 1 − x N / GaN multiple quantum wells

We have mesured the carrier recombination dynamics in InGaN/GaN multiple quantum wells over an unprecedented range in intensity. We find that at times shorter than 30\,ns, they follow an exponential form, and a power law at times longer than 1\,

A direct comparison of single-walled carbon nanotubes and quantum-wells based subpicosecond saturable absorbers for all optical signal regeneration at 1.55 μm

\mu

Enhancement of the polarization stability of a 1.55 µm emitting vertical-cavity surface-emitting laser under modulation using quantum dashes

s. To explain these biphasic dynamics, we propose a simple three-level model where a charge-separated state interplays with the radiative state through charge transfer following a tunneling mechanism. We show how the distribution of distances in charge-separated states controls the dynamics at long time. Our results imply that charge recombination happens on nearly-isolated clusters of localization centers.

Charge-transfer excitons in strongly coupled organic semiconductors

Subpicosecond optical transmission experiments are used to compare saturable absorber (SA) based on bundled single-walled carbon nanotubes (SWNT) and iron-doped InGaAs/InP epitaxial multiple quantum wells (MQW) at 1.55 μm telecom wavelength. The SA key parameters (contrast ratio, saturation fluence, and recovery time) relevant for high speed all optical signal regeneration (AOSR) are extracted from the normalized differential transmission (NDT). Although both SA exhibit good contrast ratios, SWNT show a full signal recovery as well as a much faster response time than MQW. This original work on SA shows that SWNT are excellent candidates for future low cost AOSR.

VCSEL Based on InAs Quantum-Dashes With a Lasing Operation Over a 117-nm Wavelength Span

Polarization controlled quantum dashes (QDHs) Vertical Cavity Surface Emitting Lasers (VCSELs) emitting at 1.6 µm grown on InP(001) are investigated and compared with a quantum well (QW) similar VCSEL. Polarization stability of optically-pumped VCSELs under a low frequency modulation is investigated. While major fluctuations of the polarization-resolved intensity are observed on QW-based structures, enhanced polarization stability is reached on QDH-based ones. Statistical measurements over a large number of pulses show an extremely low variation in QDH VCSEL polarized output intensity, related to the intrinsic polarization control. This makes QDH VCSEL ideal candidate to improve telecommunication networks laser performances.