Investigation of trapping levels in standard, nitrogenated and oxygenated Si p–n junctions by thermally stimulated currents
Introduction
Strong efforts are spent to develop radiation hard detectors that can operate beyond the limits of present devices [1], [2], [3]. Works are focused on finding possible solutions to limit the radiation-induced damages in silicon detectors to be used in high-level radiation environments as LHC. The key idea of the ROSE (RD48) collaboration in particular is to improve the radiation tolerance of silicon by defect engineering [4], [5]. This means deliberate addition of impurities during the growth process in order to affect the formation of electrically active defect centers and thus to control the macroscopic parameters of devices. It is believed that an impurity atom as oxygen, carbon, nitrogen, tin, acts as a vacancy sink during and following irradiation, thus limiting the detector bulk damage. The first step in understanding how microscopic defects influence the macroscopic parameters of a Si p–n junction (leakage current, depletion voltage, effective concentration of carriers) is to investigate the trapping levels associated with these defects and to find their evolution with the irradiation fluence [6], [7], [8], [9], [10]. In this paper the trapping levels induced in standard, oxygenated and nitrogenated p–n Si junctions, were investigated by the Thermally Stimulated Currents (TSC) method.
Section snippets
Experimental details
The junctions under investigation were manufactured in planar technology using different sorts of Polodovice (Czech Republic) Si wafers. The standard and oxygenated p–n junctions were processed by SINTEF (Norway) using Si wafers of 2.5 kΩ cm. The nitrogenated p–n junctions were processed by ITME-Warsaw using Si wafers of 5 kΩ cm resistivity. The oxygen concentration in oxygenated junctions is around 1016 cm−3 and the nitrogen concentration in nitrogenated junctions is of about 1015 cm−3. The area of
Results and discussion
No clear peak arises from TSC measurements performed on unirradiated samples since the current magnitude touches the detection limit of our experimental set-up. The TSC spectra for the highest irradiation fluence are shown in Fig. 1. It can be seen that the shape is preserved no matter what kind of starting Si had been used (standard, oxygenated or nitrogenated). This could be an evidence that defects induced by proton irradiation are of the same nature. There are some differences in the values
Conclusions
The TSC measurements performed on samples manufactured from standard, oxygenated and nitrogenated Si reveal the existence of three deep trapping levels induced by proton irradiation, which are located near the mid-gap, with an average introduction rate in the range of 0.9–1.2 cm−1. The enthalpy determined from Arrhenius plots is in the 0.48–0.57 eV range, in case of the dominant level 4, depending on the Si type. This level is assumed to be almost uniformly distributed in the sample. The
Acknowledgements
The authors would like to thank to Dr. F. Lemeilleur (CERN) for providing us the samples investigated in this paper.
References (20)
- et al.
Nucl. Instr. and Meth. A
(1989) - et al.
Mater. Sci. Eng. B
(1996) Nucl. Instr. and Meth. A
(1994)Nucl. Instr. and Meth. A
(1994)Nucl. Instr. and Meth. B
(1995)- et al.
Solid-State Electron.
(1971) - et al.
Nucl. Instr. and Meth. A
(2000) - L. Beattie, A. Chilingarov, P. Ratoff, T. Sloan, ROSE Technical Note 97/4, March...
- J. Matheson, M. Robbins, S. Watts, G. Hall, B. MacEvoy, RD20 Technical Note 95/43, May...
- S. Watts, Paper presented at the Proceeding vol. “Detector Seminar” of Second Workshop on Radiation Hardening of...
Cited by (4)
Thermally stimulated current method applied to highly irradiated silicon diodes
2002, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated EquipmentExperimental evidence of deep electron and hole trapping levels in high fluence proton irradiated p-n Si junctions using optical charging spectroscopy: Contribution to the R&D 48 CERN project (The ROSE collaboration)
2000, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated EquipmentStudy of the effect of annealing and physical aging on PVC by the thermally stimulated currents methods
2006, International Journal of Polymer Analysis and Characterization