Close to midgap trapping level in Co60 gamma irradiated silicon detectors

Abstract

The deep level transient spectroscopy method was applied on standard and oxygenated float-zone silicon detectors exposed to high doses of Co60–gamma irradiation. We have detected and characterized a close to midgap trapping level having an ionization energy of EC−(0.545±0.005) eV and electron/hole capture cross sections of σn=(1.7±0.2)×10−15 cm2/σp=(9±1)×10−14 cm2 respectively. This level has a strong impact on the detector performance being responsible for more than 90% of the change in the effective doping concentration. The defect is strongly oxygen related and a possible connection with the V2O complex is discussed.

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

“…2a. The quadratic dose dependence (2 nd order generation) of the I p -center was previously found both for the STFZ and DOFZ diodes up to irradiation doses of 2.80 MGy [48,50,51] and is displayed in vacancies and interstitials are mobile) it was suggested that the best candidate is the long searched for defect complex V 2 O. The V 2 O is the only one defect generated by a second order process that was evidenced by Electron Paramagnetic Resonance [53,54] as direct result of irradiation.…”

“…The I p -center is a point defect formed via a second order process that is responsible for the observed type inversion effect in oxygen lean material after γ-irradiation [48,50,51]. It was detected so far in three charge states (-, 0 and +), with two levels in the band-gap, a donor level in the lower part (E V + 0.23 eV) and an acceptor level at the middle of the gap (E C -0.55 eV).…”

Recent advancements in the development of radiation hard semiconductor detectors for S-LHC

“…In the detector processing various institutions are involved: CiS (Germany), Helsinki University of Technology (Finland), BNL (USA), IRST (Italy) and CNM (Spain). Numerous irradiation experiments have been performed with high energy (23 GeV [13,14]) and low energy (10,20,30,50 MeV [15]) protons, reactor neutrons [16], 60 Co gamma rays [16] and 900 MeV electrons [17,18]. The results from these experiments clearly reveal advantages of MCz and Cz silicon against standard and oxygen-enriched FZ material with respect to the development of the effective doping concentration N eff with increasing fluence or dose.…”

“…Here, the effective space charge of oxygenenriched silicon remains positive and gets even more positive with increasing dose in contrast to standard FZ silicon which shows a strong built-up of negative space charge. The underlying microscopic reasons for these macroscopic effects could be mainly clarified [10][11][12].…”

Defects and diffusion in high purity silicon for detector applications

“…Recently, Pintilie et al [30] have clearly demonstrated that the socalled I-centre with a level located close to midgap (~E c -0.55 eV) is a main cause for the increase of the leakage current in detectors irradiated with high fluence. Based on different experimental observations…”