Space charge sign inversion and electric field reconstruction in 24 GeV/c proton-irradiated MCz Si p+-n(TD)-n+ detectors processed via thermal donor introduction

The aim of this study is the evaluation of radiation effects in detectors based on p-type magnetic czochralski (MCz) Si that was converted to n-type by thermal donor (TD) introduction. As-processed p+-p-n+ detectors were annealed at 430 °C resulting in p+-n(TD)-n+ structures. The space charge sign and the electric field distribution E(x) in MCz Si p+-n(TD)-n+ detectors irradiated by 24 GeV/c protons were analyzed using the data on the current pulse response and the Double Peak (DP) electric field distribution model for heavily irradiated detectors. The approach considers an irradiated detector as a structure with three regions in which the electric field depends on the coordinate, and the induced current pulse response arises from the drift process of free carriers in the detector with variable electric field. Reconstruction of the E(x) profile from the pulse response shapes is performed employing a new method for DP electric field reconstruction. This method includes: (a) a direct extraction of charge loss due to trapping and (b) the fitting of a simulated pulse response to the “corrected” pulse by adjusting the electric field profiles in the three regions. Reconstruction of E(x) distribution showed that in the diodes irradiated by a proton fluence of (2–4)×1014 p/cm2 space charge sign inversion has occurred. This is the evidence that the influence of 24 GeV/c proton radiation on MCz Si p+-n(TD)-n+ detectors is similar to that on p+-n-n+ detectors based on FZ or diffusion oxygenated n-type Si.