Annealing of silicon epitaxial power diodes after irradiation at liquid He temperature

Within the framework of the collaboration between CERN and the TUM (Technical University of Munich), irradiation experiments have been carried out at liquid helium temperatures on epitaxial diodes for the superconducting magnet protection of the future Large Hadron Collider (LHC). Two sets of 10 mm diameter diode samples were submitted to an irradiation of 30 kGy dose and 6*10/sup 14/ n/cm/sup 2/ neutron fluence at liquid helium temperature. The radiation-induced degradation has been measured by the increase in the forward voltage. Afterwards, one set of diode samples was stepwise warmed up to about 250 K and, at each step, the recovery in forward voltage was monitored to determine the minimum annealing temperature. The second set of diode samples was thermally annealed with different time intervals at about 100 K and 200 K to determine the minimum annealing time.