INVESTIGATION OF EPITAXIAL SILICON LAYERS AS A MATERIAL FOR RADIATION-HARDENED SILICON DETECTORS

Epitaxial grown thick layers (greater than or equal to 100 mu m) of hi gh resistivity silicon (Epi-Si) have been investigated as a possible c andidate for radiation hardened material for detectors in high-energy physics. As grown Epi-Si layers contain high concentrations (up to 2.1 0(12) cm(-3)) Of deep levels compared with that in standard high resis tivity bulk Si. After irradiation of test diodes by protons (E-p = 24 GeV) with a fluence of 1.5.10(11) cm(-2), no additional radiation indu ced deep traps have been detected. A reasonable explanation is that th ere is a sink of primary radiation induced defects (interstitial and v acancies), possibly by as-grown defects, in epitaxial layers. :The ''s inking'' process, however, becomes non-effective at high radiation flu ences (10(14) cm(-2)) due to saturation of epitaxial defects by high c oncentration of radiation induced ones. As a result, at neutron fluenc es of 1.10(14)cm(-2) the deep level spectrum corresponds to well-known spectrum of radiation induced defects in high resistivity bulk Si. Th e net effective concentration in the space charge region equals to 3.1 0(12) cm(-3) after 3 months of room temperature storage and reveals si milar annealing behavior for epitaxial as compared to bulk silicon.