A new approach to achieving high granularity for silicon diode detectors with impact ionization gain

TL;DR

This paper introduces the Deep-Junction LGAD (DJ-LGAD), a novel silicon diode detector design that separates the high-field gain region from the readout plane, aiming to significantly enhance granularity without sacrificing charge collection efficiency.

Contribution

The paper proposes a new DJ-LGAD structure that decouples gain and readout regions, enabling higher granularity in silicon diode detectors.

Findings

Potential to achieve tens-of-micron granularity

Maintains direct charge collection on segmented electrodes

Expected to improve detector resolution significantly

Abstract

Low Gain Avalanche Diodes (LGADs) are thin (20-50 $\mu m$)silicon di ode sensors with modest internal gain (typically 5 to 50) and exceptional time resolution (17 $ps$ to 50 $ps$). However, the granularity of such devices is limited to the millimeter scale due to the need to include protection structures at the boundaries of the readout pads to avoid premature breakdown due to large local electric fields. In this paper we present a new approach -- the Deep-Junction LGAD (DJ-LGAD) -- that decouples the high-field gain region from the readout plane. This approach is expected to improve the achievable LGAD granularity to the tens-of-micron scale while maintaining direct charge collection on the segmented electrodes.