Simulation of heavily irradiated silicon pixel sensors and comparison with test beam measurements

Abstract

Abstract-Charge collection measurements performed on heavily irradiated p-spray DOFZ pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes free carrier trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant typeinverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in the ISE TCAD software can be tuned to produce a double peak electric field which describes the data reasonably well. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of charge trapping observed in the data.

Observation, modeling, and temperature dependence of doubly peaked electric fields in irradiated silicon pixel sensors

“…It is clear that the simulation can accommodate the expected leakage current which is smaller than the measured current by a factor of three. The same choice of parameters can also account for the observed rate of signal trapping [2].…”

“…A more detailed description of the double junction model and its implementation can be found in Ref. [2].…”

“…In Ref. [2] we have proved that this picture does not provide a good description of irradiated silicon pixel sensors. In addition, it was shown that it is possible to adequately describe the charge collection characteristics of a heavily irradiated silicon detector in terms of a tuned double junction model which produces a doubly peaked electric field profile across the sensor.…”

A double junction model of irradiated silicon pixel sensors for LHC

“…At F ¼ 6 Â 10 14 n eq =cm 2 the cross section ratio 1 The comparison of the measured and simulated profiles at F ¼ 6 Â 10 14 n eq =cm 2 can be found in Ref. [2].…”

“…In Ref. [2] we have proved that this picture does not provide a good description of irradiated silicon pixel sensors. In addition, it was shown that it is possible to adequately describe the charge collection characteristics of a heavily irradiated silicon detector in terms of a tuned double junction model which produces a double peak electric field profile across the sensor.…”