The influence of pixel cell layout on the timing performance of 3D sensors

TL;DR

This study investigates how pixel cell shape affects the timing performance of 3D sensors using advanced TPA-TCT measurements, highlighting the importance of design optimization for future high-precision tracking detectors.

Contribution

It introduces a novel TPA-TCT-based method for measuring sensor jitter and compares the timing uniformity of square versus hexagonal pixel layouts in 3D sensors.

Findings

Square pixel geometry provides more uniform timing response.

TPA-TCT method effectively characterizes sensor timing and jitter.

Design optimization improves 4D-tracking sensor performance.

Abstract

Three-dimensional (3D) pixel sensors are a promising technology for implementing the 4D-tracking paradigm in high-radiation environments. Despite their advantages in radiation tolerance, 3D pixel sensors exhibit non-uniform electric and weighting fields that can degrade timing performance. This study explores the impact of pixel cell geometry on the timing characteristics of 3D columnar-electrode sensors fabricated by IMB-CNM, comparing square and hexagonal layouts. The sensors were characterized using the Two-Photon Absorption Transient Current Technique (TPA-TCT), providing high-resolution three-dimensional maps of the Time-of-Arrival (ToA) of charge carriers. Measurements at multiple depths and bias voltages reveal that the square geometry yields a more uniform temporal response compared to the hexagonal configuration. Additionally, a novel TPA-TCT-based method was introduced to determine the sensor jitter, relying on the analysis of the time difference between consecutive pulses in the TPA-TCT pulse train acquired under identical conditions. These findings underline the importance of pixel design optimization for future 4D-tracking detectors and confirm the TPA-TCT method as a powerful tool for detailed timing characterization.