We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5x10^{14} Neq/cm^2 to 5.9x10^{14} Neq/cm^2. The model correctly predicts the variation in the profiles as the temperature is changed from -10C to -25C. The measured charge collection profiles are inconsistent with the linearly-varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon. The model is now being used to calibrate pixel hit reconstruction algorithms for CMS.
@article{arxiv.physics/0605215,
title = {Simulation of Heavily Irradiated Silicon Pixel Detectors},
author = {M. Swartz and V. Chiochia and Y. Allkofer and C. Amsler and D. Bortoletto and L. Cremaldi and S. Cucciarelli and A. Dorokhov and C. Hoermann and D. Kim and M. Konecki and D. Kotlinski and K. Prokofiev and C. Regenfus and T. Rohe and D. A. Sanders and S. Son and T. Speer},
journal= {arXiv preprint arXiv:physics/0605215},
year = {2010}
}
Comments
Invited talk at International Symposium on the Development of Detectors for Particle, AstroParticle and Synchrtron Radiation Experiments, Stanford Ca (SNIC06) 8 pages, LaTeX, 11 eps figures