Speaker
Description
In this presentation the relation between the leakage current and full depletion voltage to TID will be shown. From the measured I-V and C-V characteristics it is obvious that the dependence of the leakage current with respect to the TID is increasing linearly. On the other hand, the full depletion voltage and thus also the effective doping concentration shows a decreasing trend with higher TID. This gradual decrease of the effective doping concentration could be interpreted as acceptor removal or donor introduction.
For the purpose of this study $14$ diodes fabricated together with the main ATLAS pre-production sensors on n-in-p standard float zone silicon wafers with the initial resistivity of about $3\,\mathrm{k\Omega} \cdot \mathrm{cm}$ were irradiated by ${}^{60}$Co gamma rays up to a total dose of $366\,\mathrm{MRad}$ in approximate charge particle equilibrium. The samples consist of several test structures including $8\times 8\,\mathrm{mm}^2$ diodes which enables the study of leakage current and bulk capacitance. The advantage of using these diodes is the presence of contact pads on the guard ring which allows it to be grounded during I-V and C-V measurements and thus makes it possible to separate the bulk and surface current. The samples were measured before irradiation and after gamma irradiation both before and after annealing.
