GaSb-based solar cells for multi-junction integration on Si substrates

We report on the first single-junction GaSb solar cell epitaxially grown on a Si substrate. A control stand-alone GaSb solar cell was primarily fabricated, which demonstrated a 5.90% efficiency (AM1.5G). The preparation, growth and manufacturing procedures were then adapted to create the GaSb-on-Si solar cell. The hybrid device resulted in a degraded efficiency for which comparison between experimental and simulated data revealed dominant non-radiative recombination processes. Material and electrical characterization also highlighted the impact of anti-phase domains and boundaries and threading dislocation density on the shunt resistance of the cell. Nevertheless, the GaSb-on-Si cell performance is close to recent results on the integration of GaSb solar cells on GaAs, despite a much larger lattice mismatch (12% vs 8%). Routes for improvement, concerning the material quality and cell structure, are proposed. This work lays the foundations of a GaSb-based multi-junction solar cell monolithically integrated on Si

Micro-Raman for compositions characterization of selective area growth of AlxGayIn 1- x- yAs materials by metal-organic vapor-phase epitaxy

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Tensile dynamic behaviour of unidirectional glass fibre-reinforced thermoset matrix composites

The aim of this study is to determine the tensile behaviour of unidirectional glass fibre-reinforced polyester matrix composites at high strain rate (≈ 10 -1). Different orientations of the composite are tested with an hydraulic tensile machine which covers the range from static strain rate to 50 s-1. It is shown that difficulties might appear with solicitations of high velocity. The loading of the specimen becomes very complex. In this study, some improvements have been made to limit these effects. The geometry of the tests specimens is first optimised by a numerical simulation in order to obtain uniformly distributed stress and strain rate in the measurement zone. Another improvement is to choose an appropriate damping joint for limiting disturber loading. Displacement and force versus time signals obtained experimentally are free of oscillations. The longitudinal (0°) and transversal (90°) orientation of fibres in the composite are tested. For both orientation, it is observed that the mechanical properties (maximum stress, elastic modulus and failure strain) depend on the strain rate. Effect of the rate dependence on 0° specimens is moderate : the maximum stress increases slightly. For 90° specimens, the strain rate effect is much more significant on the maximum stress and the yield stress

Micro-characterization and three dimensional modeling of very large waveguide arrays by selective area growth for photonic integrated circuits

International audienceIn this work, selective area growth has been used for the realization of InP based photonic integrated circuits (PICs). To predict the strain, thickness and bandgap energy variations over large and high-density multifunctional arrays, it is necessary to precisely design the shapes and positions of the dielectric masks by computational modeling. To address the mask layout density and complexity in both longitudinal and transversal direction, the use of three dimensional vapor phase model was mandatory. In each SAG region used for individual component processing, the calculated data were compared to experimental ones acquired by synchrotron-based microbeam x-ray diffraction and by micro-photoluminescence wavelength mapping. The excellent result concordance shows that both advanced modeling and characterization techniques are of importance for PIC conception and fabrication

Demonstration of planar thick InP layers by selective MOVPE

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Cost-effective thermally-managed 1.55-μm VECSEL with hybrid mirror on copper substrate

An electroplated copper substrate was evaluated for heat dissipation in 1.55-μm optically pumped vertical extended cavity surface emitting lasers (OP-VECSELs). It is a cost-effective and flexible solution compared with the previously proposed chemical vapor deposition diamond substrate assembled by metallic bonding. Continuous-wave (CW) lasing operation was demonstrated from a device (with copper electroplated substrate) under optical pumping with pump spot diameter of 100 μm and a maximum output power of 260 mW at 0 °C; heatsink temperature was achieved. Room-temperature CW operation with an output power of 75 mW and an external quantum efficiency of 35% was achieved in an optimized plane-concave cavity. The thermal resistance and the maximum output power of VECSEL chips assembled with bonded bulk copper and electroplated copper substrates were measured and compared. A value of ∼50 K/W was estimated for both devices, and a similar rollover point was observed, which indicates that the electroplated copper solution leads to similar thermal properties as a bonded bulk copper substrate. © 2006 IEEE