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Leakage Current Simulations of Low Gain Avalanche Diode with Improved Radiation Damage Modeling

We report precise TCAD simulations of IHEP-IME-v1 Low Gain Avalanche Diode (LGAD) calibrated by secondary ion mass spectroscopy (SIMS). Our setup allows us to evaluate the leakage current, capacitance, and breakdown voltage of LGAD, which agree with measurements’ results before irradiation. And we propose an improved LGAD Radiation Damage Model (LRDM) which combines local acceptor removal with global deep energy levels. The LRDM is applied to the IHEP-IME-v1 LGAD and able to predict the leakage current well at -30 \(^{\circ}\)C after an irradiation fluence of \(\Phi_{eq}=2.5 \times 10^{15} ~n_{eq}/cm^{2}\). The charge collection efficiency (CCE) is under development.

Further reading: T. Yang, et al., Leakage Current Simulations of Low Gain Avalanche Diode with Improved Radiation Damage Modeling, Nucl. Instrum. Methods A 1040 (2022) 167111

Low Gain Avalanche Detectors with good time resolution developed by IHEP and IME for ATLAS HGTD project

This paper shows the simulation and test results of 50 μm thick Low Gain Avalanche Detectors (LGAD) sensors designed by the Institute of High Energy Physics (IHEP) and fabricated by the Institute of Microelectronics of the Chinese Academy of Sciences (IME). Three wafers have been produced with four different gain layer implant doses each. Different production processes, including variation in the n++ layer implant energy and carbon co-implantation were used. Test results show that the IHEP-IME sensors with the higher dose of gain layer have lower breakdown voltages and higher gain layer voltages from capacitance–voltage properties, which are consistent with the TCAD simulation. Beta test results show that the time resolution of IHEP-IME sensors is better than 35 ps when operated at high voltage and the collected charges of IHEP-IME sensors are larger than 15 fC before irradiation, which fulfill the required specifications of sensors before irradiations for the ATLAS HGTD project.

Further reading: M. Zhao, et al., Low Gain Avalanche Detectors with good time resolution developed by IHEP and IME for ATLAS HGTD project, Nucl. Instrum. Methods A, Volume 1033, 2022

Characterization of the first prototype NDL Low Gain Avalanche Detectors (LGAD)

Low Gain Avalanche Detectors (LGAD) are silicon particle sensors with intrinsic gain through a thin p-type multiplication layer inserted between n-type implant and p-type bulk. The first prototype of LGAD sensors in China have been developed at the Institute of High Energy Physics (IHEP) of Chinese Academic Sciences and the Novel Device Laboratory (NDL) of Beijing Normal University. With an active thickness of 33 µm, good breakdown performance, gain > 10, these sensors have reached jitter contribution of 10 ps to timing resolution with laser tests.

Further reading: Y. Yang, et al., Characterization of the first prototype NDL Low Gain Avalanche Detectors (LGAD), Nucl. Instrum. Methods A 1011 (2021) 165591

Beam test results of NDL Low Gain Avalanche Detectors (LGAD)

A High-Granularity Timing Detector (HGTD) is proposed based on the Low-Gain Avalanche Detector (LGAD) for the ATLAS experiment to satisfy the time resolution requirement for the up-coming High Luminosity at LHC (HL-LHC). We report on beam test results for two proto-types LGADs (BV60 and BV170) developed for the HGTD. Such modules were manufactured by the Institute of High Energy Physics (IHEP) of Chinese Academy of Sciences (CAS) collaborated with Novel Device Laboratory (NDL) of the Beijing Normal University. The beam tests were performed with 5 GeV electron beam at DESY. The timing performance of the LGADs was compared to a trigger counter consisting of a quartz bar coupled to a SiPM readout while extracting reference SiPM by fitting with a Gaussian function. The time resolution was obtained as 41 ps and 63 ps for the BV60 and the BV170, respectively.

Further reading: S. Xiao, et al., Beam test results of NDL Low Gain Avalanche Detectors (LGAD), Nucl. Instrum. Methods A 989 (2021) 164959

Effects of Shallow Carbon and Deep N++ Layer on the Radiation Hardness of IHEP-IME LGAD Sensors

Low-gain avalanche diode (LGAD) is the chosen technology for the ATLAS high-granularity timing detector (HGTD). According to previous studies, the acceptor removal effect due to the radiation and the single-event burnout (SEB) at high bias voltages are still a challenge for the LGAD. The Institute of High Energy Physics (IHEP), Beijing, China, cooperated with the Institute of Microelectronics (IME), Beijing, China, for the design and fabrication of the IHEP-IME LGAD sensors with shallow carbon and deep N++ layer to improve the radiation hardness of LGAD. After neutron irradiation up to \(2.5\times10^{15} n_{eq}/cm^2\), the leakage current, the collected charge, and timing resolution of the three IHEP-IME sensors measured with a beta telescope setup meet the HGTD requirements (<125 \(\mu A/cm^2\), >4fC, and <70 ps). The LGAD sensor with shallow carbon had the lowest operation voltage after irradiation and is very promising to avoid the SEB effect. A sensor with a deep N++ layer increased the breakdown voltage of the LGAD with a high dopant concentration, which could alleviate the problem of the early breakdown of radiation-hard LGAD before irradiation.

Further reading: M. Li, et al., Effects of Shallow Carbon and Deep N++ Layer on the Radiation Hardness of IHEP-IME LGAD Sensors, IEEE Transactions on Nuclear Science, Volume 69, 2022

Radiation effects on NDL prototype LGAD sensors after proton irradiation

We study the radiation effects of the Low Gain Avalanche Detector (LGAD) sensors developed by the Institute of High Energy Physics (IHEP) and the Novel Device Laboratory (NDL) of Beijing Normal University in China. These sensors have been irradiated at the China Institute of Atomic Energy (CIAE) using 100 MeV proton beam with five different fluences from 7\(\times10^{14}\rm n_{eq}/cm^2\) up to \(4.5\times10^{15}\rm n_{eq}/cm^2\). The result indicates that the effective doping concentration in the gain layer decreases with the increase of irradiation fluence, as expected by the acceptor removal mechanism. By comparing data and model gives the acceptor removal coefficient \(\rm c_{A} = \rm (5.52\pm0.58)\times10^{-16} cm^2\), which shows the NDL sensor has fairly good radiation resistance. The time resolution of the sensors after irradiation was measured at \((-30 \pm2)^{\circ}C\).

Further reading: Y. Tan, et al., Radiation effects on NDL prototype LGAD sensors after proton irradiation, Nucl. Instrum. Methods A 1010 (2021) 165559

The performance of IHEP-NDL LGAD sensors after neutron irradiation

The performances of Low Gain Avalanche Diode (LGAD) sensors from a neutron irradiation campaign with fluences of \(0.8\times10^{15}\), \(1.5\times10^{15}\) and \(2.5\times10^{15} n_{eq}/cm^2\) are reported in this article. These LGAD sensors are developed by the Institute of High Energy Physics, Chinese Academy of Sciences and the Novel Device Laboratory for the High Granularity Timing Detector of the High Luminosity Large Hadron Collider. The timing resolution and collected charge of the LGAD sensors were measured with electrons from a beta source. After irradiation with a fluence of \(2.5\times10^{15} n_{eq}/cm^2\), the collected charge decreases from 40 fC to 7 fC, the signal-to-noise ratio deteriorates from 48 to 12, and the timing resolution increases from 29 ps to 39 ps.

Further reading: M. Li, et al., The performance of IHEP-NDL LGAD sensors after neutron irradiation, 2021 JINST 16 P08053

Design of Low Gain Avalanche Detectors (LGAD) with 400 keV ion implantation energy for multiplication layer fabrication

Low Gain Avalanche Detectors (LGAD) are silicon sensors that can achieve a time resolution of better than 20 ps. The ATLAS and CMS experiments are designing LGAD detectors to address the pile-up challenge at the High Luminosity Large Hadron Collider (HL-LHC). The Institute of High Energy Physics (IHEP) has recently developed two versions of LGAD sensors. The LGAD sensors were designed using Technology Computer-Aided Design (TCAD) simulations and optimized to obtain high breakdown voltage and a suitable gain. The n-type Junction Termination Extension (N-JTE) and p-type gain layer are two critical structures for LGAD sensors that were investigated. IHEP has tuned the fabrication process of two foundries to obtain the most promising design. The first version of the IHEP LGAD sensor, with a gain higher than six and breakdown voltage higher than 400 V, was submitted to Tianjin Zhonghuan Semiconductor Company for fabrication. The second version of the LGAD sensor benefits from the higher implantation energy available at the Institute of Microelectronics (IME) to reach a gain higher than ten and breakdown voltage higher than 420 V.

Further reading: K. Wu, et al., Design of Low Gain Avalanche Detectors (LGAD) with 400 keV ion implantation energy for multiplication layer fabrication, Nucl. Instrum. Methods A 984 (2020) 164558

Design and fabrication of Low Gain Avalanche Detectors (LGAD): a TCAD simulation study

Low Gain Avalanche Detectors (LGAD) are silicon sensors with a time resolution better than 20 ps. The ATLAS and CMS experiments are designing LGAD detectors to address the pile-up challenge at the High Luminosity-Large Hadron Collider (HL-LHC). The Institute of High Energy Physics (IHEP) High-Granularity Timing Detector group has recently developed its first version of LGAD sensors. The LGAD structure was designed using Technology Computer-Aided Design (TCAD) simulations and optimized to obtain a high breakdown voltage and ideal gain. The n-type Junction Termination Extension (N-JTE) zone is a critical structure to guarantee a high breakdown voltage. The gain layer is optimized for an ideal gain factor and hence good time resolution. The optimized LGAD sensor has a gain higher than six and a breakdown voltage higher than 400 V.

Further reading: K. Wu, et al., Design and fabrication of Low Gain Avalanche Detectors (LGAD): a TCAD simulation study, JINST 15 C03008 (2020)

Radiation hardness of the low gain avalanche diodes developed by NDL and IHEP in China

This paper studies the radiation hardness of low gain avalanche detector (LGAD) developed by the Novel Device Laboratory (NDL) in Beijing and the Institute of High Energy Physics (IHEP) of Chinese Academy of Sciences, in the context of an upgrade project of the ATLAS detector for the high luminosity phase of LHC. NDL LGAD sensors with different layouts, epitaxial resistivity and doping profile were irradiated up to \(1.02\times10^{15} n_{eq}/cm^2\) by 70 MeV protons at Cyclotron and Radioisotope Center (CYRIC). The timing resolution of NDL LGAD sensors reached 50 ps and the collected charge reached 3 - 4 fC after irradiation.

Further reading: Y.Y. Fan, et al., Radiation hardness of the low gain avalanche diodes developed by NDL and IHEP in China, Nucl. Instrum. Methods A 984 (2020) 16408

Radiation Campaign of HPK Prototype LGAD sensors for the High-Granularity Timing Detector (HGTD)

We report on the results of a radiation campaign with neutrons and protons of Low Gain Avalanche Detectors (LGAD) produced by Hamamatsu (HPK) as prototypes for the High-Granularity Timing Detector (HGTD) in ATLAS. Sensors with an active thickness of 50~\(\mu\)m were irradiated in steps of roughly 2\(\times\) up to a fluence of \(3\times10^{15}~n_{eq}/cm^2\). As a function of the fluence, the collected charge and time resolution of the irradiated sensors will be reported for operation at \(-30^{\circ}C\).

Further reading: X. Shi, et al., Radiation campaign of HPK prototype LGAD sensors for the High-Granularity Timing Detector (HGTD), Nucl. Instrum. Methods A 979 (2020) 164382

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