Laser enhanced field evaporation of surface atoms in Laser-assisted Atom Probe Tomography (La-APT) can simultaneously excite phtotoluminescence in semiconductor or insulating specimens. An atom probe equipped with appropriate focalization and collection optics has been coupled with an in-situ micro-Photoluminescence (µPL) bench that can be operated during APT analysis. The Photonic Atom Probe instrument we have developped operates at frequencies up to 500 kHz and is controlled by 150 fs laser pulses tunable in energy in a large spectral range (spanning from deep UV to near IR). Micro-PL spectroscopy is performed using a 320 mm focal length spectrometer equipped with a CCD camera for time-integrated and with a streak camera for time-resolved acquisitions. An exemple of application of this instrument on a multi-quantum well oxide heterostructure sample illustrates the potential of this new generation of tomographic atom probe.
GaInN-based photovoltaic (PV) devices are highly promising for application to optical wireless power transmission (OWPT) systems as well as solar cells. This paper reports the research results of Ga0.9In0.1N multiple-quantum-well (MQW) PV cells on sapphire, focusing primarily on the growth temperature managements in metalorganic chemical vapor deposition (MOCVD) processes. As a result of the MOCVD study, the epilayer qualities in the PV cell structures improved significantly through the adoption of an optimized growth temperature for the GaInN MQWs and the two-step growth for the top p-GaN layers. Furthermore, the improved epilayer qualities resulted in the decrease in carrier recombination currents and series resistance for the forward diode characteristics without a light illumination. Subsequently, a sample with the improved qualities exhibited a higher open-circuit voltage and a higher fill factor in the PV characteristics. Eventually, the highest power conversion efficiency (PCE) in this study was measured to be 1.6% at a 1-sun solar spectrum and 42.7% at a monochromatic light illumination with 389 nm in wavelength and 5 mW cm−2 in optical power density. The dependency of the PV performance on the optical power densities at a monochromatic light illumination predicted that a higher PCE value may be achievable at a higher optical-power-density illumination. This is a very promising prediction when considering the practical application to OWPT systems.
The influence of temperature on the intensity of light emitted by as well as the carrier life time of a standard AlGaAs based light emitting diode has been investigated in the temperature range from 345 to 136 K. The open-circuit voltage decay (OCVD) technique has been used for measured the carrier lifetime. Our experimental results reveal a 16% average increase in intensity and a 163.482-19.765 ns variation in carrier lifetime in the above temperature range. Further, theoretical and experimental analysis show that for negligible carrier density the intensity is inversely proportional to carrier lifetime for this sample.
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