Radiation damage in silicon exposed to high-energy protons

Abstract

Photoluminescence, infrared absorption, positron annihilation, and deep-level transient spectroscopy ͑DLTS͒ have been used to investigate the radiation damage produced by 24 GeV/ c protons in crystalline silicon. The irradiation doses and the concentrations of carbon and oxygen in the samples have been chosen to monitor the mobility of the damage products. Single vacancies ͑and self-interstitials͒ are introduced at the rate of ϳ1 cm −1 , and divacancies at 0.5 cm −1 . Stable di-interstitials are formed when two self-interstitials are displaced in one damage event, and they are mobile at room temperature. In the initial stages of annealing the evolution of the point defects can be understood mainly in terms of trapping at the impurities. However, the positron signal shows that about two orders of magnitude more vacancies are produced by the protons than are detected in the point defects. Damage clusters exist, and are largely removed by annealing at 700 to 800 K, when there is an associated loss of broad band emission between 850 and 1000 meV. The well-known W center is generated by restructuring within clusters, with a range of activation energies of about 1.3 to 1.6 eV, reflecting the disordered nature of the clusters. Comparison of the formation of the X centers in oxygenated and oxygen-lean samples suggests that the J defect may be interstitial related rather than vacancy related. To a large extent, the damage and annealing behavior may be factorized into point defects ͑monitored by sharp-line optical spectra and DLTS͒ and cluster defects ͑monitored by positron annihilation and broadband luminescence͒. Taking this view to the limit, the generation rates for the point defects are as predicted by simply taking the damage generated by the Coulomb interaction of the protons and Si nuclei.

Deep level contribution to the carrier generation and recombination in high resistivity Si irradiated by neutrons

“…3 and 4. These results confirm the data obtained during the preliminary investigation presented in [13], and also theoretical models [4] that a system of many vacancies and different other defect transformations has many possibilities, and the performed measurements give the "fingerprint" of the sample but do not characterise all created centres. The analysis of photoconductivity spectrum dependence on temperature shows that an additional photoconductivity band appears at higher temperatures.…”

“…Defect generation by hadron irradiation in silicon, and the change of defect types due to a high vacancy migration rate during sample annealing and reactions between them, with interstitial atoms and impurities are well analysed [3,4]. The vacancies are mostly generated inside the clusters, but they are also in the bulk of crystal; therefore, the redistribution and modification of defects inside and outside the cluster change the compensation of the bulk, the parameters of traps and recombination centres.…”

Radiation-induced point- and cluster-related defects with strong impact on damage properties of silicon detectors

“…It is therefore most likely produced by small PKA energies as expected from Coulomb interaction of charged hadrons or electrons. It is however not seen after γ irradiation and could tentatively be attributed to the tri-interstitial (minimum threshold energy 75eV) as observed in photoluminescence measurements [46]. For the electron irradiations only oxygen lean float zone diodes (STFZ) had been used and therefore the generation of the BD-defect, as visible in the hadron irradiated oxygen rich EPI-diodes is very unlikely.…”

“…were already investigated in detail and no correlation with the "macroscopic" behavior of the diodes could be established [35][36][37][38][39][40][41][42][43][44][45][46]. The main characteristics of defects, from the electrical point of view, are the emission rates of carriers in the conduction and valence bands given by:…”

Insights on the atomistic origin of X and W photoluminescence lines inc-Si fromab initiosimulations

“…The centers responsible for these lines are present in ion-implanted [5,6,7,8,9] as well as in high energy electron-and proton-irradiated c-Si [10,11]. As W and X centers are generated during irradiation processes, they coexists with a large variety of defects which makes their identification through experiments difficult.…”