Hamburg 2016 – scientific programme

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T: Fachverband Teilchenphysik

T 53: Halbleiterdetektoren III (Strahlenhärte)

T 53.9: Talk

Tuesday, March 1, 2016, 18:45–19:00, VMP8 HS

Absorption of light, drift velocity, and trapping times in highly irradiated silicon pad sensors — •Christian Scharf, Robert Klanner, and Erika Garutti — Institute for Experimental Physics, Hamburg University, Luruper Chaussee 149, D-22761 Hamburg, Germany

The aim of this work is to obtain information on the drift velocities and trapping rates in radiation damaged silicon sensors as a function of electric field and dose. For highly irradiated silicon sensors the electric field under reverse bias takes the shape of a double junction with high field near the implants and a region of lower field in between. For this condition it is difficult to determine separately the electric field, the trapping and multiplication of charge carriers, and the drift velocity; all of which are functions of the irradiation and the position in the sensor. However, for forward bias the electric field and the trapping rates are expected to be independent of position. We analyze transient current measurements of forward biased silicon pad sensors irradiated with proton doses above 10¹⁵ n_eq/cm² . The transients are induced by charges produced by sub-ns laser light of wavelengths of 670 and 1060 nm. In the analysis we considered that radiation-induced defects in the silicon can result in a decrease of the light absorption length, resulting in an increase of the number of electron-hole pairs generated by infrared light. This effect influences the determination of the charge collection efficiency of highly irradiated silicon sensors using infrared laser pulses, which is a method frequently used. The analysis method and first results will be presented.