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12 pages, 2699 KB

Open AccessArticle

TCAD Simulation of Two Photon Absorption—Transient Current Technique Measurements on Silicon Detectors and LGADs

by Sebastian Pape, Michael Moll, Marcos Fernández García and Moritz Wiehe

Sensors 2024, 24(24), 8032; https://doi.org/10.3390/s24248032 - 16 Dec 2024

Cited by 2 | Viewed by 2231

Device simulation plays a crucial role in complementing experimental device characterisation by enabling deeper understanding of internal physical processes. However, for simulations to be trusted, experimental validation is essential to confirm the accuracy of the conclusions drawn. In the framework of semiconductor detector characterisation, one powerful tool for such validation is the Two Photon Absorption-Transient Current Technique (TPA-TCT), which allows for highly precise, three-dimensional spatially-resolved characterisation of semiconductor detectors. In this work, the TCAD framework Synopsys Sentaurus is used to simulate depth-resolved TPA-TCT data for both p-type pad detectors (PINs) and Low Gain Avalanche Detectors (LGADs). The simulated data are compared against experimentally measured TPA-TCT results. Through this comparison, it is demonstrated that TCAD simulations can reproduce the TPA-TCT measurements, providing valuable insights into the TPA-TCT itself. Another significant outcome of this study is the successful simulation of the gain reduction mechanism, which can be observed in LGADs with increasing densities of excess charge carriers. This effect is demonstrated in an p-type LGAD with a thickness of approximately 286 µm. The results confirm the ability of TCAD to model the complex interaction between carrier dynamics and device gain. Full article

(This article belongs to the Special Issue Radiation Sensors and Detectors: Materials, Principles and Applications (2nd Edition))

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17 pages, 3942 KB

Open AccessArticle

Study of Neutron-, Proton-, and Gamma-Irradiated Silicon Detectors Using the Two-Photon Absorption–Transient Current Technique

by Sebastian Pape, Marcos Fernández García, Michael Moll and Moritz Wiehe

Sensors 2024, 24(16), 5443; https://doi.org/10.3390/s24165443 - 22 Aug 2024

Cited by 2 | Viewed by 2008

Abstract

The Two-Photon Absorption–Transient Current Technique (TPA-TCT) is a device characterisation technique that enables three-dimensional spatial resolution. Laser light in the quadratic absorption regime is employed to generate excess charge carriers only in a small volume around the focal spot. The drift of the excess charge carriers is studied to obtain information about the device under test. Neutron-, proton-, and gamma-irradiated p-type pad silicon detectors up to equivalent fluences of about 7 × 10¹⁵

n_{eq} / c m^{2}

and a dose of

186 M r a d

are investigated to study irradiation-induced effects on the TPA-TCT. Neutron and proton irradiation lead to additional linear absorption, which does not occur in gamma-irradiated detectors. The additional absorption is related to cluster damage, and the absorption scales according to the non-ionising energy loss. The influence of irradiation on the two-photon absorption coefficient is investigated, as well as potential laser beam depletion by the irradiation-induced linear absorption. Further, the electric field in neutron- and proton-irradiated pad detectors at an equivalent fluence of about 7 × 10¹⁵

n_{eq} / c m^{2}

is investigated, where the space charge of the proton-irradiated devices appears inverted compared to the neutron-irradiated device. Full article

(This article belongs to the Special Issue Radiation Sensors and Detectors: Materials, Principles and Applications)

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11 pages, 2076 KB

Open AccessArticle

Techniques for the Investigation of Segmented Sensors Using the Two Photon Absorption-Transient Current Technique

by Sebastian Pape, Esteban Currás, Marcos Fernández García and Michael Moll

Sensors 2023, 23(2), 962; https://doi.org/10.3390/s23020962 - 14 Jan 2023

Cited by 5 | Viewed by 2966

Abstract

The two photon absorption-transient current technique (TPA-TCT) was used to investigate a silicon strip detector with illumination from the top. Measurement and analysis techniques for the TPA-TCT of segmented devices are presented and discussed using a passive strip CMOS detector and a standard strip detector as an example. The influence of laser beam clipping and reflection is shown, and a method that allows to compensate these intensity-related effects for investigation of the electric field is introduced and successfully employed. Additionally, the mirror technique is introduced, which exploits reflection at a metallised back side to enable the measurement directly below a top metallisation while illuminating from the top. Full article

(This article belongs to the Special Issue Radiation Sensors and Detectors: Materials, Principles and Applications)

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10 pages, 1610 KB

Open AccessArticle

Mitigation of Single-Event Effects in SiGe-HBT Current-Mode Logic Circuits

by Md Arifur R. Sarker, Seungwoo Jung, Adrian Ildefonso, Ani Khachatrian, Stephen P. Buchner, Dale McMorrow, Pauline Paki, John D. Cressler and Ickhyun Song

Sensors 2020, 20(9), 2581; https://doi.org/10.3390/s20092581 - 1 May 2020

Cited by 5 | Viewed by 4386

Abstract

It has been known that negative feedback loops (internal and external) in a SiGe heterojunction bipolar transistors (HBT) DC current mirrors improve single-event transient (SET) response; both the peak transient current and the settling time significantly decrease. In the present work, we demonstrate how radiation hardening by design (RHBD) techniques utilized in DC bias blocks only (current mirrors) can also improve the SET response in AC signal paths of switching circuits (e.g., current-mode logic, CML) without any additional hardening in those AC signal paths. Four CML circuits both with and without RHBD current mirrors were fabricated in 130 nm SiGe HBT technology. Two existing RHBD techniques were employed separately in the current mirrors of the CML circuits: (1) applying internal negative feedback and (2) adding a large capacitor in a sensitive node. In addition, these methods are also combined to analyze the overall SET performance. The single-event transients of the fabricated circuits were captured under the two-photon-absorption laser-induced single-event environment. The measurement data clearly show significant improvements in SET response in the AC signal paths of the CML circuits by using the two radiation hardening techniques applied only in DC current mirrors. The peak output transient current is notably reduced, and the settling time upon a laser strike is shortened significantly. Full article

(This article belongs to the Special Issue Radiation-Hardened Sensors, Circuits and Systems)

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