Compensated LGAD optimisation through van der Pauw test structures

TL;DR

This paper investigates a novel compensated LGAD design for improved radiation resistance, using van der Pauw test structures and simulations to analyze doping evolution and donor removal under irradiation.

Contribution

It introduces an innovative application of van der Pauw test structures to monitor doping changes in compensated LGADs during irradiation, supported by experimental and simulation analysis.

Findings

Donor removal at high initial concentrations affects LGAD performance.

Carbon co-implantation slows acceptor removal, enhancing radiation tolerance.

Van der Pauw structures effectively estimate doping changes post-irradiation.

Abstract

A new gain implant design has recently been introduced to enhance the radiation resistance of low-gain avalanche diodes (LGADs) to the extreme fluences anticipated in future hadron colliders like FCC-hh. This design utilises an engineered compensation of two opposing types of doping implants, requiring a thorough analysis of their evolution due to irradiation. To this end, the experimental measurements of their initial test structures have been compared with Technology CAD simulations both before and after irradiation. From the measurement-simulation comparison regarding C-V characteristics, the donor removal at high initial donor concentrations ($>10^{16}$ at/cm$^3$) used in Compensated LGADs has been studied, along with how donor co-implantation influences the beneficial effect of carbon to slow acceptor removal. Furthermore, an innovative application of van der Pauw test structures, typically employed by foundries to monitor process quality, has been implemented. The doping removal of the single implants used in Compensated LGADs has been estimated by examining the variation in sheet resistance with irradiation through these structures.