Time dependence of charge losses at the Si-SiO2 interface in p+n-silicon strip sensors

TL;DR

This study investigates how charge collection in p+n silicon strip sensors near the Si-SiO2 interface varies over time and with environmental conditions, especially after high-dose X-ray irradiation, revealing humidity-dependent charge loss dynamics.

Contribution

It provides new insights into the time-dependent charge losses at the Si-SiO2 interface in irradiated sensors and introduces analysis techniques for understanding these effects.

Findings

Charge losses depend on biasing history, humidity, and irradiation.

Time constants for charge loss increase significantly at low humidity.

Incomplete charge collection varies between electrons and holes over time.

Abstract

The collection of charge carriers generated in p+n strip sensors close to the Si-SiO2 interface before and after 1 MGy of X-ray irradiation has been investigated using the transient current technique with sub-nanosecond focused light pulses of 660 nm wavelength, which has an absorption length of 3.5 um in silicon at room temperature. The paper describes the measurement and analysis techniques used to determine the number of electrons and holes collected. Depending on biasing history, humidity and irradiation, incomplete collection of either electrons or holes is observed. The charge losses change with time. The time constants are different for electrons and holes and increase by two orders of magnitude when reducing the relative humidity from about 80 % to less than 1 %. An attempt to interpret these results is presented.