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

Abstract

Epitaxial grown thick layers (>IO0 pm) 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 2.1Oi2 cm") of deep levels compared with that in standard high resistivity bulk Si. After irradiation of test diodes by protons (EP = 24 GeV) with a fluence of 1.5-10'' 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 (loJ4 cm-') due to saturation of epitaxial defects by high concentration of radiation induced ones. As a result, at neutron fluence of l-10i4cm'2 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 3.10i2 cm-3 after 3 months of room temperature storage and reveals similar annealing behavior for epitaxial as compared to bulk silicon.

Arsenic-Doped High-Resistivity-Silicon Epitaxial Layers for Integrating Low-Capacitance Diodes

“…Moreover, due to the neglected leakage current components, it is safe to claim that the generation lifetime for the 40-μm-thick epi-layer is >2.5 ms. This is more than an order of magnitude higher than the ~100 μs lifetime of the thick, high-resistivity epi-layers reported in [ 6 ].…”

“…The use of epitaxially grown, thick, high-resistivity Si layers for radiation detection has been investigated in the past for the ability to enhance the radiation hardness at high radiation fluences [ 6 , 7 ]. Layers were grown >100-μm-thick with a resistivity of a few kΩcm that contained a high concentration of deep level traps.…”

Depletion voltage and charge collection for highly irradiated silicon microstrip detectors with various initial resistivities

“…In the following, we will, for comparison, refer all depletion voltages to a common thickness of 300 µm, which means dividing the measured depletion voltages by a factor (d/300) 2 , where d is the thickness of the detector in µm.…”

“…There is evidence that using low-resistivity n-bulk material for detector fabrication will reduce the final depletion voltage after large fluences [2,3]. This evidence is mostly from a) static C-V measurements where the depletion voltage is determined from the fact that, after depletion, the body capacitance is independent of the bias voltage; and b) test pad detectors made specifically for general study on radiation damage problem.…”

Recent developments of CERN RD39 cryogenic tracking detectors collaboration

“…This parameter is affected by both the detector sensitive volume (depletion thickness) and charge trapping by radiation-induced defect levels. Two deep levels are considered to be main responsible for the effective doping concentration increase and are taken into account in modeling the radiation effects [3][4][5][6]. These levels have been obtained by fitting the experimental data : a deep donor level (DD) 0.48 eV above the valence band and a deep acceptor level (DA) 0.527 eV below the conduction band with a capture cross section of both levels of approx.…”