We report current-voltage and spectral response characteristics of high density InAs/GaAs quantum dot (QD) solar cells with different positions where dots are located. The short circuit current density (Jsc), open circuit voltage (Voc), and external quantum efficiency of these cells under air mass 1.5 are presented and compared with a GaAs reference cell. An extended photoresponse in contrast to the GaAs reference cell was confirmed for all these cells. The effect of inserting QD layers into emitter and base region on device performance is shown. The Jsc is reduced, while the Voc is maintained. The cell with QDs located toward the base side shows better performance, confirmed by both current-voltage and spectral response measurements.
We report high density quantum dots (QDs) formation with optimized growth temperature and V/III ratio. At lower growth temperature, QD density is increased, due to smaller surface migration length of In adatoms. With higher V/III, the QD density is higher but it results in large clusters formation and decreases the QD uniformity. The QD solar cell was fabricated and examined. An extended spectral response in contrast to the GaAs reference cell was presented but the external quantum efficiency at energies higher than GaAs band gap is reduced, resulting from the degradation for the emitter above the strained QD layers.
Geometric phase analysis has been applied to high resolution aberration corrected (scanning) transmission electron microscopy images of InAs/GaAs quantum dot (QD) materials. We show quantitatively how the lattice mismatch induced strain varies on the atomic scale and tetragonally distorts the lattice in a wide region that extends several nm into the GaAs spacer layer below and above the QDs. Finally, we show how V-shaped dislocations originating at the QD/GaAs interface efficiently remove most of the lattice mismatch induced tetragonal distortions in and around the QD.
The MetOp-SG satellite program is an EUMETSAT/-ESA cooperation with the objective to obtain long-term collection of remotely sensed data of uniform quality for meteorology and climate monitoring state analysis and forecast. A series of three satellite pairs (MetOp-SG-A1, -A2 and -A3) are to be launched, ensuring continuity of data to beyond 2045.The Infrared Atmospheric Sounder Interferometer Next Generation (IASI-NG), being developed by CNES, is one of the instruments on the MetOp-SG-A's. The IASI-NG is a Fourier Transform Infrared Spectrometer scanning the atmosphere to provide data for atmospheric gas characterisation.Kongsberg Defence and Aerospace (KDA) has developed the LAser Source Electronics (LASE) for the IASI-NG instrument. The LASE provides a wavelength-stabilized optical source to be injected into the IASI-NG with a wavelength stability within ± 0.00015 nm throughout the instrument lifetime. The wavelength is locked and controlled using a feedback-loop containing a gas cell filled with 13 C2H2. The LASE shall in addition perform the conversion of the optical signal from the interferometer into analogue electrical signal which can be further processed. The lifetime includes 15.75 years of storage and 7.75 years in space.The challenge of meeting the required Polarisation Extinction Ratio (PER) for a fiber optical system, as the one in LASE, is discussed.
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