Design and testing of LGAD sensor with shallow carbon implantation

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 for Minimum Ionizing Particles (MIP). 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 x 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.

Automated summary

The low gain avalanche detectors (LGADs) provide excellent time resolution of about 30 ps for Minimum Ionizing Particles (MIP) due to their thin sensors with fast charge collection and internal gain. However, the upgraded Large Hadron Collider (LHC) in 2028 will cause radiation damage and deterioration of LGAD performance due to high collision and particle rates. To mitigate such effects, the Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS) has developed a process to enrich the gain layer of LGADs with carbon, reducing the acceptor removal effect caused by radiation. These modified LGAD sensors have demonstrated adequate charge collection (>4 fC) and time resolution (<50 ps) at voltages <400 V, even after exposure to a maximum fluence of 2.5 x 10(15) neutron equivalent fluence of 1 MeV at ATLAS High Granularity Timing Detector (HGTD).