Performance of Ga_1−xAl_xAs light emitting diodes in radiation environments

Abstract

Addition of aluminum as a cation substituent in GaAs improves the relative radiation hardness of the GaAs light emitting diode, as deduced from both gamma and neutron irradiation experiments to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> rads (Si) and 3.5&time;10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> neutrons/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively. The gamma damage coefficient, K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</inf> , shows a marked and unexpected decrease from 52 (rads (Si) .s) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> to ∼ 2 (rads(Si) .s)−1 in the composition range from GaAs to ∼ Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.90</inf> Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</inf> AS. Above 10 percent Al content, the damage coefficient changes only slightly. On the other hand, the neutron damage coefficient K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> shows a gradual change over the entire compositional range from 0 to 34 percent aluminum. Annealing of the gamma-irradiated samples indicates that the 240° C stage noted for GaAs and attributed to an arsenic vacancy is reduced with addition of aluminum. On the other hand the annealing of the Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1−x</inf> Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> As samples following neutron irradiation indicates that the annealing characteristics are virtually independent of the aluminum composition. For both types of irradiation there is a shift of the peak emission wavelength to shorter wavelengths following irradiation.