Ultra-Slow Dynamic Annealing of Neutron-induced Defects in n-type Silicon: Role of Charge Carriers

TL;DR

This study investigates how neutron flux influences defect annealing in n-type silicon, revealing a flux-dependent dynamic annealing process with implications for silicon defect management.

Contribution

It demonstrates a flux dependence of defect annealing in silicon under neutron irradiation, highlighting differences from proton bombardment due to charge carrier effects.

Findings

Higher neutron flux reduces defect accumulation.

Flux sensitivity is significantly lower than in proton irradiation.

Charge carriers influence defect diffusion and dissociation rates.

Abstract

Neutron bombardments with equivalent fluence (1$\times$10$^{10}$ cm$^{-2}$) and different fluxes ($2.5\times$10$^5$ cm$^{-2}$s$^{-1}$ to $1\times$10$^7$ cm$^{-2}$s$^{-1}$) have been performed on three kinds of bipolar devices with n-type silicon as active regions. The measured increase of base currents and input bias currents are found to decrease with increasing neutron flux, implying that the strength of the dynamic annealing of divacancy defects in n-type silicon follows a positive flux dependence. Such a flux dependence is the same as that observed in ions implantation using protons, but the evident flux sensitivity in our experiment is 4 orders of magnitude lower than that of proton bombardment, despite the similarity in the masses and energies of the two particles. The huge discrepancy of flux range is attributed to the presence of vast charge carriers in proton bombardments, which strongly accelerate the dynamic annealing of defects by enhancing the diffusion velocity of Si interstitials and dissociation rate of defect clusters. Our work would contribute to the understanding of the defect annealing processes in silicon.