Light‐emitting diodes fabricated from the GaAs1−xPxalloy system undergo degradation upon neutron irradiation. It has been found that the smallest change in efficiency occurs when the composition of the alloy is betweenx= 0.30 andx= 0.75. The change in minority‐carrier lifetime, however, is approximately constant throughout the entire alloy range. It is suggested that the relative insensitivity to neutron irradiation of the efficiency in the alloy rangex= 0.30–0.75 is connected with the inherent disorder already present within the GaAs1−xPxalloy system.