Hamburg 2016 – scientific programme

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T: Fachverband Teilchenphysik

T 53: Halbleiterdetektoren III (Strahlenhärte)

T 53.4: Talk

Tuesday, March 1, 2016, 17:30–17:45, VMP8 HS

X-ray irradiation effects of interface traps and trapped-oxide charge at the Si-SiO₂ interface of segmented silicon sensors — •Ioannis Kopsalis, Eckhart Fretwurst, Erika Garutti, Robert Klanner, and Joern Schwandt — Institute for Experimental Physics, Hamburg University, Luruper Chaussee 149, D-22761 Hamburg, Germany

The surface radiation damage of SiO₂ grown on high-ohmic Si, as used for the fabrication of segmented silicon sensors, has been investigated. Circular p- and n-MOSFETs, biased in accumulation and inversion at a field in the SiO₂ of about 500 kV/cm, have been irradiated by X-rays up to a dose of about 17 kGy(SiO₂) in different irradiation steps. Before and after each irradiation, the gate voltage has been cycled from inversion to accumulation conditions and back, and from the dependence of the drain-source current, on gate voltage, the threshold voltage of the MOSFET and the hole and electron mobility at the Si-SiO₂ interface determined.
From the threshold voltage, the effective oxide-charge density is calculated. Using the subthreshold-current technique the contribution of interface traps, in the lower and the upper part of the energy Si bandgap, and of fixed oxide-charge to the effective oxide-charge density has been estimated. Results on the dose dependence of the above quantities, the charging-up and discharging of border traps when changing the gate voltage, and the hole and electron mobilities at the Si-SiO₂ interface are presented.