Depth-dependent inter-pixel distance in trench-isolated LGADs for shallow radiation detection
Abstract
The fill factor of finely segmented low-gain avalanche detectors (LGAD) is limited by the effective inter-pixel distance (IPD), particularly when charge is generated far from the gain layer. In this work, 200 μ m thick trench-isolated LGADs (TI-LGADs) fabricated by Micron Semiconductor Ltd. were characterized using single-photon and two-photon absorption transient current technique measurements at ELI Beamlines to determine the dependence of IPD on interaction depth, illumination direction, and gain-layer doping. The measurements show that the effective IPD is smallest near the trench side of the device and increases as charge generation occurs deeper in the sensor bulk, with a minimum measured IPD of approximately 7 μ m. Devices with higher gain-layer doping exhibit larger IPD, indicating a trade-off between gain and effective fill factor, while depth-resolved measurements reveal enhanced charge collection at the trench edge consistent with a localized high-field region at the gain-layer/trench interface. These results show that, in thick TI-LGADs, back-side shallow absorption corresponds to charge generation far from the multiplication region and can therefore lead to an increased IPD, which may limit the performance of small-pixel designs. The findings identify an important design constraint for TI-LGADs intended for applications involving shallow energy deposition under back-side illumination.
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BibTeX
@article{zareef2026depthdependent,
title = {{Depth-dependent inter-pixel distance in trench-isolated LGADs for shallow radiation detection}},
author = {Fasih Zareef and Parisa Rezaei Mianroodi and Mateusz Rebarz and Pablo Fernandez-Martínez and Richard Bates and Dzmitry Maneuski and Mark Bullough and Agnieszka Obłakowska-Mucha and Tomasz Szumlak and Neil Moffat},
journal = {Scientific Reports},
year = {2026},
month = oct,
doi = {10.1038/s41598-026-74942-1},
url = {https://www.nature.com/articles/s41598-026-74942-1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Depth-dependent inter-pixel distance in trench-isolated LGADs for shallow radiation detection
AU - Fasih Zareef
AU - Parisa Rezaei Mianroodi
AU - Mateusz Rebarz
AU - Pablo Fernandez-Martínez
AU - Richard Bates
AU - Dzmitry Maneuski
AU - Mark Bullough
AU - Agnieszka Obłakowska-Mucha
AU - Tomasz Szumlak
AU - Neil Moffat
PY - 2026
DA - 2026/10/24
JO - Scientific Reports
DO - 10.1038/s41598-026-74942-1
UR - https://www.nature.com/articles/s41598-026-74942-1
AB - The fill factor of finely segmented low-gain avalanche detectors (LGAD) is limited by the effective inter-pixel distance (IPD), particularly when charge is generated far from the gain layer. In this work, 200 μ m thick trench-isolated LGADs (TI-LGADs) fabricated by Micron Semiconductor Ltd. were characterized using single-photon and two-photon absorption transient current technique measurements at ELI Beamlines to determine the dependence of IPD on interaction depth, illumination direction, and gain-layer doping. The measurements show that the effective IPD is smallest near the trench side of the device and increases as charge generation occurs deeper in the sensor bulk, with a minimum measured IPD of approximately 7 μ m. Devices with higher gain-layer doping exhibit larger IPD, indicating a trade-off between gain and effective fill factor, while depth-resolved measurements reveal enhanced charge collection at the trench edge consistent with a localized high-field region at the gain-layer/trench interface. These results show that, in thick TI-LGADs, back-side shallow absorption corresponds to charge generation far from the multiplication region and can therefore lead to an increased IPD, which may limit the performance of small-pixel designs. The findings identify an important design constraint for TI-LGADs intended for applications involving shallow energy deposition under back-side illumination.
SN - 2045-2322
ER -