ABSTRACT
This chapter focuses on how large fluences of neutrons and protons change the properties of UFSDs. The extraction of VGLC becomes more difficult with increasing irradiation fluence. As the doping of the gain implant decreases and that of the bulk increases, the change of slope in the 1/C2(V) curve becomes less and less evident. One important effect that might contribute to maintaining a high value of gain in UFSDs is bulk multiplication. The bias voltage can be raised substantially at high enough fluences, generating an electric field in the bulk. Since the electric field in the bulk is actually increasing as a function of irradiation, the simulation predicts an increasing gain as a function of fluence. UFSDs owe their excellent performances to the presence of gain.
