<prompt> Radiation emits by Ir-1920.5 Mev0.6 Mev0.66 Mev0.47 Mev  <response>: Irradiation damage in Insub 0.53Gasub 0.47As p-i-n photodiodes by 1-MeV fast neutrons is studied as a function of fluence for the first time. The degradation of the electrical and optical performance of diodes increases with increasing fluence. The induced lattice defects in the Insub 0.53Gasub 0.47As epitaxial layers and the InP substrate are studied by DLTS methods.In the Insub 0.53Gasub-0.47As epitaxial layers, hole and electron capture levels are induced by irradiation. The influence of radiation source on device degradation is then discussed by comparison to 1-MeV electrons with respect to the numbers of knock-on atoms and the nonionizing energy loss NIEL. In order to examine the recovery behavior, isochronal thermal annealing is carried out for temperatures ranging from 75 to 300spl degC.After 300spl degC thermal annealing, the light current only recovers to 20 of pre-irradiation for a fluence of 1spl times10sup 13 ncmsup 2, while it recovers to 53 for a fluence of 1spl times10sup 15 ecmsup 2.The different recovery behavior is thought to be due to a different type of radiation damage. 