Study of radiation damage in silicon detectors for high ... - F9
Study of radiation damage in silicon detectors for high ... - F9
Study of radiation damage in silicon detectors for high ... - F9
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6Inuence <strong>of</strong> Bias VoltageIt was a general belief that bias voltage does not aect creation or time development<strong>of</strong> <strong>radiation</strong> <strong>in</strong>duced defects <strong>in</strong> <strong>silicon</strong>. It also seemed consistent with the rst ir<strong>radiation</strong>smade <strong>in</strong> the scope <strong>of</strong> this work (diodes SA and P0). As we understand so far thereasons that the bias eect was not seen were <strong>in</strong> only partially bias<strong>in</strong>g the samples andfrequent time <strong>in</strong>tervals with no bias at all. This must have reduced the eect <strong>of</strong> the biassuciently to attribute the rema<strong>in</strong><strong>in</strong>g dierence between biased and unbiased samples toother parameters (dosimetry, measurement errors etc). Thus it was rather late be<strong>for</strong>e thiseect was observed and systematically studied. This reects <strong>in</strong> the results <strong>of</strong> previouschapters, where most <strong>of</strong> the samples were only partially biased. Parameters obta<strong>in</strong>ed bythose measurements are thus a comb<strong>in</strong>ation <strong>of</strong> those <strong>for</strong> biased and those <strong>for</strong> unbiasedsamples.6.1 Inuence on Neff6.1.1 Time Development <strong>of</strong> Unbiased SamplesTo study reverse anneal<strong>in</strong>g <strong>of</strong> unbiased samples a pair <strong>of</strong> oat-zone Micron planar processed11cm 2 diodes, with <strong>in</strong>itial FDV <strong>of</strong> about 18 V, were irradiated and stored withoutbias. Diodes were irradiated <strong>in</strong> parallel, to a uence <strong>of</strong> 4:1 10 13 n/cm 2 1 MeV neutronequivalent (ir<strong>radiation</strong> ux 1:8 10 9 n/cm 2 s). After 1 day at room temperature, timedevelopment was accelerated by heat<strong>in</strong>g to 60 C. Time development together with a rstorder (eq. 2.57) and a second order (eq. 2.61) t <strong>for</strong> both diodes is shown <strong>in</strong> g. 6.1.Results <strong>of</strong> the ts are given <strong>in</strong> table 6.1.Comparison <strong>of</strong> the ts with measured data (g. 6.1) shows better agreement <strong>for</strong> thesecond order expression. This is conrmed by an about 5 times lower 2 /ndf <strong>for</strong> the secondorder ansatz (table 6.1). S<strong>in</strong>ce the complete volume <strong>of</strong> both samples was undepleted dur<strong>in</strong>g89