IMPROVEMENT IN SWITCHING CHARACTERISTICS OF SILICON DIODES THROUGH A SELECTIVE ZONE OF DEFECTS PRODUCED BY 6 MEV ELECTRONS

The reverse recovery time of silicon diodes was reduced from 800 ns to 150 ns, by creating a narrow zone of radiation induced defects in the n-side of each diode with 6 MeV electrons. This 75 mu m wide zone of defects was located in the central part of the diode. where, during th e reverse operation, the concentration of minority carriers is high bu t the recombination rate is very low. The forward voltage drop across the diode increased marginally, by 0.1 V, over its preirradiation valu e of 0.9 V. The trade-off between the reverse recovery time and the fo rward voltage drop of these partially irradiated diodes was found to b e superior to the diodes irradiated fully by positioning the junction layer, either parallel or perpendicular to the incident 6 MeV electron beam and also to the diodes irradiated either from the p- or n-side w ith 2 MeV protons. These results indicate that this method is suitable for making fast switching diodes without adopting the gold diffusion process.