Short-Term Annealing in Silicon Devices Following Pulsed 14-MeV Neutron Irradiation

A study of short-term annealing in 14-MeVneutron-irradiated silicon devices has been performed employing a dense-plasma-focus fusion neutron generator (typical fluences: 1 to 5 × 1010 n/cm2; pulsewidth ~100 nsec). Fusion-fission comparisons are made basedon companion experiments performed at a Triga reactor and on fast-burst reactor data obtained by Gregory and Sander. For solar cells and bipolar transistors, 14-MeV annealing factors are observed to be larger than their fission counterparts at early times following irradiation. At 20 msec, the fusion-fission annealing-factor ratio has a value typically in the range from 1.3 to 1.4. The unstable damage ratio at this same time is ~1.7 for equal amounts of stable damage. Annealing data for 14-MeV neutron-irradiated solar cells are shown to correlate quite well with electron density. For transistors, the maximum fusion annealing factor observed is ~5 at ~100 ¿sec for both npn and pnp devices. A qualitative model, based on differing defect densities in fusion and fission disordered regions, is proposed to account for the data. Additionally, a method for estimating transient annealing behavior as a function of neutron energy is presented.