Development of LGAD sensors with a thin entrance window for soft X-ray detection

Zhang, J.; Barten, R.; Baruffaldi, F.; Bergamaschi, A.; Borghi, G.; Boscardin, M.; Brückner, Martin; Carulla, M.; Vignali, M. Centis; Dinapoli, R.; Ebner, Simon Gregor; Ficorella, F.; ̈dh, E. Fröjj; Greiffenberg, D.; Ali, O. Hammad; Heymes, J.; Hasanaj, S.; Hinger, V.; King, Tsu‐Jae; Kozłowski, Paweł; Lopez-Cuenca, C.; Mezza, D.; Moustakas, Konstantinos; Mozzanica, A.; Paternoster, G.; Ronchin, S.; Ruder, C.; Schmitt, B.; Thattil, D.

doi:10.1088/1748-0221/17/11/c11011

Cited by 16 publications

(21 citation statements)

References 12 publications

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“…The spatial uniformity of the multiplication is essential for X-ray position-sensitive detectors, in particular for experiments that require high spatial resolution by interpolation using charge sharing [10]. The iLGAD sensors used in this work coupled to the MÖNCH detector demonstrated single-photon detection down to a photon energy of 452 eV, when illuminated with fluorescence X-rays [11].…”

Section: Introductionmentioning

confidence: 97%

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Characterization of iLGADs using soft X-rays

Liguori,

Barten,

Baruffaldi

et al. 2023

J. Inst.

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Experiments at synchrotron radiation sources and X-ray Free-Electron Lasers in the soft X-ray energy range (250 eV–2 keV) stand to benefit from the adaptation of the hybrid silicon detector technology for low energy photons. Inverse Low Gain Avalanche Diode (iLGAD) sensors provide an internal gain, enhancing the signal-to-noise ratio and allowing single photon detection below 1 keV using hybrid detectors. In addition, an optimization of the entrance window of these sensors enhances their quantum efficiency (QE). In this work, the QE and the gain of a batch of different iLGAD diodes with optimized entrance windows were characterized using soft X-rays at the Surface/Interface:Microscopy beamline of the Swiss Light Source synchrotron. Above 250 eV, the QE is larger than 55% for all sensor variations, while the charge collection efficiency is close to 100%. The average gain depends on the gain layer design of the iLGADs and increases with photon energy. A fitting procedure is introduced to extract the multiplication factor as a function of the absorption depth of X-ray photons inside the sensors. In particular, the multiplication factors for electron- and hole-triggered avalanches are estimated, corresponding to photon absorption beyond or before the gain layer, respectively.

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Section: Introductionmentioning

confidence: 97%

“…To optimize the EW, the metalization is replaced with a thin passivation, composed of Si 3 N 4 and SiO 2 layers (figure 2) [11]. In particular, the SiO 2 layer is used to reduce the recombination effects of charge carriers at the surface by compensating the silicon dangling bonds with the thermally grown oxide.…”

Section: Introductionmentioning

confidence: 99%

Characterization of iLGADs using soft X-rays

Liguori,

Barten,

Baruffaldi

et al. 2023

J. Inst.

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“…The minimum detectable energy (5σ 2 x 2 clusters ) with single photon resolution for 2 would be around 1.5 keV, and around 1 keV for 5 . Below these limits, sensors with internal gain such as LGADs are necessary [11].…”

Section: X-ray Detection Performancementioning

confidence: 99%

Balancing gain and dynamic range in a 25 µm pitch hybrid pixel detector

Heymes,

Barten,

Baruffaldi

et al. 2024

J. Inst.

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MÖNCH is a hybrid pixel detector featuring 25 µm pixel pitch and analogue readout for X-ray imaging at synchrotron radiation (SR) facilities. Sub-pixel spatial resolution has been demonstrated using charge sharing and interpolation algorithms. The current prototype version, MÖNCH0.4, features 19 different pixel architectures to assess the design choices and components for an optimised architecture to be used at SR facilities, and to explore the potential use of dynamic gain switching in fine pitch pixels for applications at X-ray free electron lasers (XFELs). Previous characterisation results of the pixel architectures without dynamic gain switching have shown noise levels as low as 21.7 e- r.m.s., which have now been pushed to sub-20 e- r.m.s at room temperature using standard 300 µm-thick silicon sensors. Achieving low noise values however requires high conversion gain and necessitates design choices such as the simplification of the pixel architecture (e.g. by limiting the available choice of in-pixel gains). These compromises ultimately restrain the available dynamic range and prevent the use of MÖNCH with low-gain avalanche diodes (LGADs) or high-Z sensors because of the large signals (internal amplification and high photon energies, respectively) and of large leakage currents. In this paper, we will introduce the MÖNCH project followed by a description of the current prototype along with characterisation results of the pixel architectures without dynamic gain switching for synchrotron applications with an emphasis on noise and dynamic range. These experimental results will be used to fine-tune the design of MÖNCH0.5 to validate the final pixel design. This small prototype should also include additional features from the continuous developments of the PSD detector group towards a full-scale 2 × 3 cm2 MÖNCH1.0.

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“…The measured QE of a standard silicon sensor for 800 eV X-ray photons is less than 50% as presented in ref. [1]. Therefore, an optimization of the EW technology is required to reduce the recombination in the silicon and at the silicon surface, at the same time that the transmittance in the surface layer is increased.…”

Section: Introductionmentioning

confidence: 99%

“…The use of the new entrance window technology together with LGADs technology allows the single-photon detection of X-rays with energies lower than 800 eV, as already demonstrated by J. Zhang et al ref. [1].…”

Section: Introductionmentioning

confidence: 99%

Study of the internal quantum efficiency of FBK sensors with optimized entrance windows

et al. 2023

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Single-photon detection of X-rays in the energy range of 250 eV to 1 keV is difficult for hybrid detectors because of the low quantum efficiency and low signal-to-noise ratio. The low quantum efficiency is caused by the absorption of soft X-rays in the entrance window of the silicon sensors. The entrance window consists of an insensitive layer on the surface and a highly doped layer, which is typically from a few hundred nanometers to a couple of micrometers thick and is comparable to the absorption depth of soft X-ray photons (e.g. the attenuation length of 250 eV X-ray photons is ∼100 nm in silicon). The low signal-to-noise ratio is mainly caused by the small signal amplitude (e.g. ca. 70 electrons for 250 eV X-ray photons in silicon) with respect to the electronic noise. To improve the quantum efficiency, the entrance window must be optimized by minimizing the absorption of soft X-rays in the insensitive layer, and reducing charge recombination at the Si-SiO2 interface and in the highly doped region. Low gain avalanche diodes (LGADs) with a multiplication factor between 5 and 10 increase the signal amplitude and therefore improve the signal-to-noise ratio for soft X-rays, enabling single-photon detection down to 250 eV. Combining LGAD technology with an optimized entrance window technology can thus allow hybrid detectors to become a useful tool also for soft X-ray detection. In this work we present the optimization of the entrance window by studying the internal quantum efficiency of eight different process technology variations. The sensors are characterized using light emitting diodes with a wavelength of 405 nm. At this wavelength, the light has an absorption depth of 125 nm, equivalent to that of 276 eV X-rays. The best variation achieves an internal quantum efficiency of 0.992 for 405 nm UV light. Based on this study, further optimization of the quantum efficiency for soft X-rays detection is planned.

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Development of LGAD sensors with a thin entrance window for soft X-ray detection

Cited by 16 publications

References 12 publications

Characterization of iLGADs using soft X-rays

Characterization of iLGADs using soft X-rays

Balancing gain and dynamic range in a 25 µm pitch hybrid pixel detector

Study of the internal quantum efficiency of FBK sensors with optimized entrance windows

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