High-sensitivity measurements of the magnetostriction constant ${\lambda }_s$ have been performed in the nearly zero magnetostriction (${\mathrm{Co}}_{0.94}$ ${\mathrm{Fe}}_{0.06}$ ${)}_{75}$ ${\mathrm{Si}}_{15}$ ${\mathrm{B}}_{10}$ metallic glass as a function of the stress and temperature after pulse-annealing treatments. A stress dependence of ${\lambda }_s$ in this amorphous alloy is reported for the first time. At room temperature a slope of about -2×${10}^{\mathrm{-}7}$ ${\mathrm{GPa}}^{\mathrm{-}1}$ has been determined leading to a change in the sign of the magnetostriction constant in some circumstances. For determination of the thermal variation of ${\lambda }_s$, the temperature was changed by means of the alternating current flowing through the sample during the measurement, which was done by the small-angle magnetization-rotation (SAMR) method. The compensation temperatures, i.e., those temperatures at which the value of ${\lambda }_s$ vanishes in going from negative to positive, were determined after isochronal annealing. In this way, the evolution of the single-ion and two-ion contributions to the magneto- striction was monitored during the structural relaxation. The ratio between the two contributions follows a chemical short-range-order kinetics. The stress dependence of the single-ion and two-ion contributions was deduced from measurements of the stress dependence of the magnetostriction at different temperatures.

A temperature accelerated life test on commercial concentrator lattice‐matched GaInP/GaInAs/Ge triple‐junction solar cells has been carried out. The acceleration of the aging has been accomplished by subjecting the solar cells at temperatures markedly higher than the nominal working temperature inside a concentrator, and the nominal photo‐current condition (820 X) has been emulated by injecting current in darkness. Three tests at different temperatures have been carried out. The failure distributions across the three test temperatures have been fitted to an Arrhenius–Weibull model. An Arrhenius activation energy of 1.59 eV was determined from the fit. The reliability functions and parameters of these solar cells at two nominal working conditions (80 and 100 °C) have been obtained. In both cases, the instantaneous failure rate function monotonically increases, that is, the failures are of the wear‐out kind. We have also observed that the reliability data are very sensitive to the nominal temperature condition. In fact, at a nominal working condition of 820 X and 80 °C, assuming that the concentration module works 5 h per day, the warranty time obtained for a failure population of 5% has been 113 years. However, for a nominal working condition of 820 X and 100 °C, the warranty time obtained for a failure population of 5% has been 7 years. Therefore, in order to offer a long‐term warranty, the working temperature could be a key factor in the design of the concentration photovoltaic systems. Copyright © 2014 John Wiley & Sons, Ltd.

Evaluating the reliability, warranty period, and power degradation of high concentration solar cells is crucial to introducing this new technology to the market. The reliability of high concentration GaAs solar cells, as measured in temperature accelerated life tests, is described in this paper. GaAs cells were tested under high thermal accelerated conditions that emulated operation under 700 or 1050 suns over a period exceeding 10 000 h. Progressive power degradation was observed, although no catastrophic failures occurred. An Arrhenius activation energy of 1.02 eV was determined from these tests. The solar cell reliability [R(t)] under working conditions of 65°C was evaluated for different failure limits (1–10% power loss). From this reliability function, the mean time to failure and the warranty time were evaluated. Solar cell temperature appeared to be the primary determinant of reliability and warranty period, with concentration being the secondary determinant. A 30‐year warranty for these 1 mm²‐sized GaAs cells (manufactured according to a light emitting diode‐like approach) may be offered for both cell concentrations (700 and 1050 suns) if the solar cell is operated at a working temperature of 65°C. Copyright © 2012 John Wiley & Sons, Ltd.

Modulated molecular beams phase-locked to reflection high-energy electron diffraction (RHEED) oscillations have been used to grow low-temperature GaAs quantum wells (QW) confined by AlAs/GaAs short-period superlattices (SL). Two different phase-locked modulation growth modes were attempted and compared. In the first mode, only the As₄ beam was interrupted periodically in-phase with the monolayer growth cycle. In the second one, both Ga (or Al) and As₄ incident beams were modulated synchronously with the monolayer period. Both growth methods were seen to produce high-optical-quality QW and SL's layers at low-growth temperatures (T _s≃400°C).