The role of primary point defects in the degradation of silicon detectors due to hadron and lepton irradiation

Abstract

The principal obstacle to long-time operation of silicon detectors at the highest energies in the next generation of experiments arises from bulk displacement damage which causes significant degradation of their macroscopic properties. The analysis of the behaviour of silicon detectors after irradiation conduces to a good or reasonable agreement between theoretical calculations and experimental data for the time evolution of the leakage current and effective carrier concentration after lepton and gamma irradiation and large discrepancies after hadron irradiation and this in conditions where a reasonable agreement is obtained between experimental and calculated concentrations of complex defects. In this contribution, we argue that the main discrepancies could be solved naturally considering as primary defects the self-interstitials, classical vacancies and the new predicted fourfold coordinated silicon pseudovacancy defects. This new defect is supposed to be introduced uniformly in the bulk during irradiation, has deep energy level(s) in the gap and it is stable in time. Considering the mechanisms of production of defects and their kinetics, it was possible to determine indirectly the characteristics of the Si FFCD defect: energy level in the band gap and cross section for minority carrier capture. In the frame of the model, the effects of primary defects on the degradation of silicon detectors are important in conditions of continuous long time irradiation and /or high fluences.

Some Contributions to the Understanding of the Puzzle of Physical Processes of Degradation in Irradiated Silicon

“…Predicted by Goedecker and coworkers [2], some characteristics were determined by the authors in Ref. [1]. In agreement with the before mentioned results, the defect has an energy level in the band gap between Ec -(0.46 0.48) eV, a capture cross section between (5-10)X105 cm2 and a ratio 6p/ cy -1 5.…”

Stress influenced trapping processes in Si based multi-quantum well structures and heavy ions implanted Si

“…In the same time, as a consequence of the energy they impart to the atomic system during their stopping, they produce primary irradiation defects as vacancies and interstitials. Their mutual interaction, and their interaction with the impurities present into Si is the source of common point defects V 2 , VO, C i O i and C i C s [9].…”

Energy Loss and Damage Production by Heavy Ions and Strange Quark Matter in Silicon

“…Then, the primary knock-on nucleus, if its energy is large enough, can produce the displacement of a new nucleus, and the process continues as long as the energy of the colliding nucleus is higher than the threshold for atomic displacements. The primary mechanism for defect formation during irradiation in semiconductors is the collision of the incoming particle with the atoms of the crystal, which leads to the departure of an atom to a rather large distance from its original site, i.e., to the formation of separated Frenkel pairs (vacancies and interstitials) as well as of the Si FFCD defect, that introduces a new type of symmetry in lattice [11,12]:…”