Design and testing of LGAD sensor with shallow carbon implantation

TL;DR

This paper presents the development and testing of LGAD sensors with shallow carbon implantation to improve radiation tolerance, maintaining high charge collection and timing performance after high neutron fluence exposure.

Contribution

It introduces a carbon-enriched gain layer process for LGADs that enhances radiation resistance and preserves performance at high fluences.

Findings

LGAD sensors with carbon enrichment retain charge collection > 4 fC after high fluence.

Time resolution remains below 50 ps at voltages under 400 V.

Operation voltages are below thresholds for single event burnout.

Abstract

The low gain avalanche detectors (LGADs) are thin sensors with fast charge collection which in combination with internal gain deliver an outstanding time resolution of about 30 ps. High collision rates and consequent large particle rates crossing the detectors at the upgraded Large Hadron Collider (LHC) in 2028 will lead to radiation damage and deteriorated performance of the LGADs. The main consequence of radiation damage is loss of gain layer doping (acceptor removal) which requires an increase of bias voltage to compensate for the loss of charge collection efficiency and consequently time resolution. The Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS) has developed a process based on the Institute of Microelectronics (IME), CAS capability to enrich the gain layer with carbon to reduce the acceptor removal effect by radiation. After 1 MeV neutron equivalent fluence of 2.5$\times$10$^{15}$ n$_{eq}$/cm$^{2}$, which is the maximum fluence to which sensors will be exposed at ATLAS High Granularity Timing Detector (HGTD), the IHEP-IME second version (IHEP-IMEv2) 50 $\mu$m LGAD sensors already deliver adequate charge collection > 4 fC and time resolution < 50 ps at voltages < 400 V. The operation voltages of these 50 $\mu$m devices are well below those at which single event burnout may occur.