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

The aim of this study is evaluation of radiation effects in detectors based on p-type MCZ Si, and converted afterwards to n-type by thermal donor (TD) introduction. As-processed p⁺-p-n⁺ detectors were annealed at 450degC resulting in p⁺-n(TD)-n⁺ structures. Space charge sign and 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 current pulse response and the approach for double peak electric field distribution E(x) in heavily irradiated detectors. The approach considers 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 drift process in the detector with variable electric field. Reconstruction of E(x) profile from pulse response shapes is performed employing new method for DP electric field reconstruction. This method includes: (a) direct extraction of charge loss due to trapping, and (b) the fitting of 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 2-4times10¹⁴ p/cm² space charge sign inversion has been 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.