Analysis and optimal design of surface radiation hard p⁺n Si pixel detector: impact on signal collection using TCAD simulation

Abstract

Surface radiation hard p⁺n Si pixel detectors are required for the science experiment at a synchrotron, and the major challenge is to improve the charge collection efficiency in the high-voltage X-ray-irradiated Si pixel detectors. Several experiments have been performed at DESY, Hamburg, Germany, within the AGIPD consortium on the test structures to extract the microscopic parameters of the X-ray-induced surface radiation damage in the detectors. The results on the microscopic parameters are fed into Cogenda Visual TCAD commercial simulation program to compare the experimental results and simulation data. A very good agreement has been recorded between the results and simulation data. In this paper, several surface radiation hard p⁺n Si pixel design options have been explored using a microscopic model for the improvement in the high-voltage stability of the detector and high-charge collection efficiency. A new intra-guard ring is incorporated in the design of the two adjacent p⁺ pixels equipped with symmetric in and outward metal overhang extensions. The proposed surface radiation hard optimal design can enhance the electric field in the gutter region of the n-Si-bulk, a region which can have a very low electric field, which is just below the Si-SiO₂ interface of the detectors, and this is the major concern for the charge loss in the X-ray-irradiated detectors. The results are discussed in detail using electric field distribution in the different designs of the pixel detectors for the different X-ray doses, and an optimized p⁺n Si pixel detector design with an intra-guard ring structure is proposed for the experiment.

KEYWORDS:

• P⁺n Si pixel detector
• surface damage
• E-field
• CCE
• TCAD simulation

Acknowledgement

The author would like to thank the Department of Science and Technology (DST), Government of India, for providing the DST Inspire fellowship and also a special thanks to Mr Amit Saini (Director, Cadre Design Systems), who has provided me immense support in learning the Cogenda Visual TCAD software.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Ministry of Science and Technology, Department of Science and Technology, Govt. of India [grant number IF190198].

Notes on contributors

Nitu Saini

Nitu Saini received her MSc. Degree in physics from Chandigarh University, Mohali, Punjab, India. Thereafter, she is working as a full time research scholar in Department of physics, Chandigarh University, Punjab, India, under the guidance of Prof. (Dr.) Ajay Kumar Srivastava. She has been awarded with one of the India’s prestigious fellowship i.e. ‘Innovation in Science Pursuit for Inspired Research (INSPIRE-Fellowship)’ by Department of Science and Technology (DST), Govt. of India for her Ph.D. thesis on the project of ‘Study of X-ray induced damage investigation in the different design of detectors for the next generation photon science experiment’.

Shilpa Patyal

Shilpa Patyal received her M.Sc. Degree in physics from Chandigarh University, Punjab, India. Thereafter, she is working as a full-time research scholar in the Department of physics, Chandigarh University, Punjab, India, under the guidance of Prof. (Dr.) Ajay Kumar Srivastava.

Balwinder Kaur

Balwinder Kaur received her M.Sc. Degree in physics from Punjabi University, Patiala, Punjab, India. Thereafter, she is working as a research scholar in the Department of physics, Chandigarh University, Punjab, India, under the guidance of Prof. (Dr.) Ajay Kumar Srivastava.

Ajay Kumar Srivastava

Ajay Kumar Srivastava received his Ph.D. degree in Experimental High Energy Physics ‘Development of Si strip detector for the ECAL of the CMS Experiment at CERN, Geneva’ at the Department of Physics, University of Delhi, India. Thereafter, he worked as a Postdoctoral fellow at the Institute for Experimental Physics, University of Hamburg, Germany on two prestigious projects in Germany DESY with Professor Dr. Robert Klanner at DESY; ‘short strip p⁺n detector for inner tracking of CMS tracker upgrade’ and ‘x-ray p⁺n pixel detector for the European XFEL’. He was a visiting scientist at CERN, Geneva from (2008–2010). He then did a second postdoctoral work ‘development of DSSD for Belle2’ at the Tata Institute of Fundamental Research (TIFR), Mumbai with Prof. Tariq Aziz. In 2012, he worked as a Senior Scientist at FEI Company (now Thermo Fisher Scientific Instruments), USA. Ajay is currently a full Professor (Physics) at Chandigarh University, Mohali, India involved in the research & development of p⁺n strip detectors for the phase-2 upgrade of the CMS tracker upgrade for the HL-LHC (2026) and x ray p⁺n pixel detector for the next generation photon science experiments. He has received several awards, fellowships and honours, such as a CIMO Fellow, UGC, New Delhi, DST (RA, Scientist), Govt. India, Industrial Resident, IMEC, Belgium, DAE RA-3 Honorarium, TIFR, Mumbai, India just to mention a few. His research is published in more than 80 international peer reviewed research Journals & worked in the International European Experiments (CMS CERN, CEC CMS) & CERN RD50 Collaboration.