Low-field carrier mobilities in silicon irradiated to extreme fluences

TL;DR

This study quantifies how low-field carrier mobilities in <100> silicon degrade with extreme neutron irradiation fluences up to 10^18 cm^-2 across a temperature range of 230K to 260K.

Contribution

It provides a detailed fit model for mobility degradation due to ionized impurity scattering in heavily irradiated silicon, validated by TCAD simulations.

Findings

Mobility decreases by approximately 60% at the fluence relevant for FCC-hh detector layers.

The fit model accurately describes mobility as a function of fluence and temperature.

TCAD simulations effectively estimate carrier concentrations used in the mobility model.

Abstract

The low-field carrier mobilities in <100> silicon were quantified as a function of the 1$\,$MeV neutron-equivalent fluence up to $10^{18}\,$cm$^{-2}$ and for temperatures between 230$\,$K and 260$\,$K. Current measurements were fitted using a mobility model for scattering at ionized impurities. Technology-aided design (TCAD) simulations were compared to measurements and used to estimate the carrier concentrations, which are parameters in the fit. The fit model describes the data very well, both as a function of fluence and the temperature. At a fluence of $6 \cdot 10^{17}\,$cm$^{-2}$, which is expected for the innermost detector layers at the proposed Future Circular Hadron Collider (FCC-hh), the sum of the mobilities of electrons and holes was found to decrease by $\sim60$%.