Performance of Ga1−xAlxAs light emitting diodes in radiation environments

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 10⁸ rads (Si) and 3.5&time;10¹³ neutrons/cm², respectively. The gamma damage coefficient, Ky, shows a marked and unexpected decrease from 52 (rads (Si) .s)⁻¹ to ∼ 2 (rads(Si) .s)−1 in the composition range from GaAs to ∼ Ga.90Al 10AS. Above 10 percent Al content, the damage coefficient changes only slightly. On the other hand, the neutron damage coefficient Kn 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 Ga1−xAlxAs 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.