# Fabrication and performance of AC-coupled LGADs

## TL;DR

This paper reports on the design, fabrication, and testing of AC-coupled LGAD sensors that aim to improve spatial resolution while maintaining excellent timing performance for applications in physics and imaging.

## Contribution

It introduces the AC-coupled LGAD approach, enabling fine pad pixelation without sacrificing timing, and demonstrates prototype performance with various particle beams.

## Key findings

- Prototypes show effective charge collection and timing performance.
- AC-coupled LGADs achieve finer spatial resolution.
- Successful testing with radioactive source particle beams.

## Abstract

Detectors that can simultaneously provide fine time and spatial resolution have attracted wide-spread interest for applications in several fields such as high-energy and nuclear physics as well as in low-energy electron detection, photon science, photonics and imaging. Low-Gain Avalanche Diodes (LGADs), being fabricated on thin silicon substrates and featuring a charge gain of up to 100, exhibit excellent timing performance. Since pads much larger than the substrate thickness are necessary to achieve a spatially uniform multiplication, a fine pad pixelation is difficult. To overcome this limitation, the AC-coupled LGAD approach was introduced. In this type of device, metal electrodes are placed over an insulator at a fine pitch, and signals are capacitively induced on these electrodes. At Brookhaven National Laboratory, we have designed and fabricated prototypes of AC-coupled LGAD sensors. The performance of small test structures with different particle beams from radioactive sources are shown.