The origin of double peak electric field distribution in heavily irradiated silicon detectors

The first observation of double peak (DP) electric field distribution in heavily neutron irradiated (>1014 n/cm2) semiconductor detectors has been published about 6 yr ago. However, this effect was not quantitatively analyzed up to now. The explanation of the DP electric field distribution presented in this paper is based on the properties of radiation induced deep levels in silicon, which act as deep traps, and on the distribution of the thermally generated free carrier concentration in the detector bulk. In the frame of this model, the earlier published considerations on the so-called “double junction (DJ) effect” are discussed as well. The comparison of the calculated electric field profiles at different temperatures with the experimental ones allows one to determine a set of deep levels. This set of deep levels, and their charge filling status are essential to the value and the distribution of space charge in the space charge region in the range of 305–240 K, which is actual temperature range for the main experiments at LHC where silicon detectors are used. This set of deep levels includes the levels located close to the midgap and does not contain the defects with the largest introduction rate −(Ci–Oi) and (V–V).