# Inverse Low Gain Avalanche Detectors (iLGADs) for precise tracking and timing applications

## TL;DR

This paper introduces inverse LGAD (iLGAD) sensors with a continuous gain layer to improve position and timing resolution in particle detectors, addressing fill-factor issues present in traditional LGADs.

## Contribution

The paper presents the design and initial performance results of the first iLGAD prototypes, demonstrating a solution to fill-factor and resolution limitations of conventional LGADs.

## Key findings

- iLGADs achieve uniform gain across the sensitive area.
- Prototype testing shows improved timing resolution.
- iLGADs have potential for enhanced particle tracking applications.

## Abstract

Low Gain Avalanche Detector (LGAD) is the baseline sensing technology of the recently proposed Minimum Ionizing Particle (MIP) end-cap timing detectors (MTD) at the Atlas and CMS experiments. The current MTD sensor is designed as a multi-pad matrix detector delivering a poor position resolution, due to the relatively large pad area, around 1 $mm^2$; and a good timing resolution, around 20-30 ps. Besides, in his current technological incarnation, the timing resolution of the MTD LGAD sensors is severely degraded once the MIP particle hits the inter-pad region since the signal amplification is missing for this region. This limitation is named as the LGAD fill-factor problem. To overcome the fill factor problem and the poor position resolution of the MTD LGAD sensors, a p-in-p LGAD (iLGAD) was introduced. Contrary to the conventional LGAD, the iLGAD has a non-segmented deep p-well (the multiplication layer). Therefore, iLGADs should ideally present a constant gain value over all the sensitive region of the device without gain drops between the signal collecting electrodes; in other words, iLGADs should have a 100${\%}$ fill-factor by design. In this paper, tracking and timing performance of the first iLGAD prototypes is presented.