Effect of proton irradiation induced localized defect clusters on recovery time and leakage current in silicon photoconductive semiconductor switches

Abstract

Pulse recovery time in semiconducting devices depends strongly on minority carrier lifetime, bandgap-type-dependent recombination, impurity concentration, and subband placement. In indirect bandgap solids, such as silicon, it is dominated by Shockley–Reed–Hall (SRH) recombination via trap-based recombination centers yielding slow recombination. The sluggish recombination then limits the pulse repetition rate and consequently the average power to a load. For decades, fabrication and irradiation techniques, such as Au- and Pt-diffusion, and energized electron-, proton-, and alpha particle-beam bombardment have been used to adjust minority carrier lifetime in silicon. These techniques generate shallow- and/or deep-level lattice defects to promote/retard trap-assisted SRH recombination. Despite investigating the characteristics of the generated defects on target material, the prior-art falls short in comprehensively addressing their effects on device-level architecture, specifically photoconductive switching devices. In this work, the effect of proton irradiation-induced localized crystal defect clusters on minority carrier lifetime in silicon photoconductive semiconductor switches is investigated when bombarded with 2.5–5 MeV beam energies with fluences between 9 × 1012–11 × 1013 cm−2 at room temperature. Photo-illuminated recovery characteristics for proton-beam (p-beam) irradiated device models with three distinct defect profiles have been studied using Silvaco TCAD and results have been compared with the electron-beam (e-beam) irradiation model with three different distinct defect profiles. At 30× lower defect density, recovery time trends in the p-beam irradiated device model were seen to be on the same order of magnitude as the e-beam irradiated model. At similar defect densities (1 × 1016 cm−3), the profile with a uniformly distributed bulk defect profile performed 10× better from a recovery time viewpoint compared with the e-beam irradiation. Furthermore, three orders of magnitude reduction in leakage currents were noticed in p-beam irradiated models.