Investigation of epitaxial silicon layers as a material for radiation hardened silicon detectors

摘要

Epitaxial grown thick layers (>100 micrometers) of high resistivity silicon (Epi-Si) have been investigated as a possible candidate of radiation hardened material for detectors for high-energy physics. As grown Epi-Si layers contain high concentration (up to 2 x 10 to the 12th power/cu cm) of deep levels compared with that in standard high resistivity bulk Si. After irradiation of test diodes by protons (E(sub p) = 24 GeV) with a fluence of 1.5 x 10 to the 11th power/sq cm, no additional radiation induced deep traps have been detected. A reasonable explanation is that there is a sink of primary radiation induced defects (interstitial and vacancies), possibly by as-grown defects, in epitaxial layers. The 'sinking' process, however, becomes non-effective at high radiation fluences (10 to the 14th power/sq cm) due to saturation of epitaxial defects by high concentration of radiation induced ones. As a result, at neutron fluence of 1 x 10 to the 14th power/sq cm the deep level spectrum corresponds to well-known spectrum of radiation induced defects in high resistivity bulk Si. The net effective concentration in the space charge region equals to 3 x 10 to the 12th power/cu cm after 3 months of room temperature storage and reveals similar annealing behavior for epitaxial as compared to bulk silicon.