Characterization of energy levels related to impurities in epitaxial 4H-SiC ion implanted p+n junctions

Abstract The distribution of energy levels within the bandgap of epitaxial 4H-SiC p + /n junctions was studied. The junction was obtained by Al ion implantation on a nitrogen doped n-type epitaxial substrate. Thermally stimulated currents/capacitance (TSC/TSCAP) as well as current/capacitance deep level transient spectroscopy (I- and C-DLTS) were carried out over a wide temperature range (20–400 K). The two TSC/DLTS peaks associated with N-doping were detected for the first time and their trap signatures determined. Two hole traps relating to deep and shallow boron confirm that a boron contamination occurred during crystal growth. A negligible concentration of the Z 1/2 level, which is usually the dominant level produced by irradiation of ion implant, was measured. The concentrations of all observed traps were significantly lower than nitrogen one, which determines the doping. This evidence supports the high quality of the processed junctions, making these devices particularly attractive for future use in particle detection as well as in optoelectronic applications

Thermal donors formation via isothermal annealing in magnetic Czochralski high resistivity silicon

A quantitative study about the thermal activation of oxygen related thermal donors in high resistivity p-type magnetic Czochralski silicon has been carried out. Thermal donor formation has been performed through isothermal annealing at 430°C up to a total time of 120min. Space charge density after each annealing step has been measured by transient current technique. The localized energy levels related to thermal double donors (TD) have been observed and studied in details by thermally stimulated currents (TSCs) in the range of 10–70K, and activation energies E and effective cross sections σ have been determined for both the emissions TD0∕+ (E=75±5meV, σ=4×10−14cm2) and TD+∕+ (E=170±5meV, σ=2×10−12cm2). The evolution of the space charge density caused by annealing has been unambiguously related to the activation of TDs by means of current deep level transient spectroscopy TSC, and current transients at constant temperature i(t,T). Our results show that TDs compensate the initial boron doping, eventually provoking the sign inversion of the space charge density. TD's generation rate has been found to be linear with the annealing time and to depend critically on the initial interstitial oxygen concentration, in agreement with previous models developed on low resistivity silicon

Ultra-fast silicon detectors

Abstract We propose to develop a fast, thin silicon sensor with gain capable to concurrently measure with high precision the space (∼10 μm) and time (∼10 ps) coordinates of a particle. This will open up new application of silicon detector systems in many fields. Our analysis of detector properties indicates that it is possible to improve the timing characteristics of silicon-based tracking sensors, which already have sufficient position resolution, to achieve four-dimensional high-precision measurements. The basic sensor characteristics and the expected performance are listed, the wide field of applications are mentioned and the required R&D topics are discussed

Charge collection and capacitance–voltage analysis in irradiated n-type magnetic Czochralski silicon detectors

Abstract The depletion depth of irradiated n-type silicon microstrip detectors can be inferred from both the reciprocal capacitance and from the amount of collected charge. Capacitance voltage ( C – V ) measurements at different frequencies and temperatures are being compared with the bias voltage dependence of the charge collection on an irradiated n-type magnetic Czochralski silicon detector. Good agreement between the reciprocal capacitance and the median collected charge is found when the frequency of the C – V measurement is selected such that it scales with the temperature dependence of the leakage current. Measuring C – V characteristics at prescribed combinations of temperature and frequency allows then a realistic estimate of the depletion characteristics of irradiated silicon strip detectors based on C – V data alone

Development of 3D detectors at FBK-irst

We report on the development of 3D detectors at Fondazione Bruno Kessler - irst in the framework of the CERN RD-50 Collaboration. Technological and design aspects dealing with the 3D Single Type Column detectors are reviewed, and selected results from the electrical and functional characterization of prototypes are reported and discussed. A new detector concept, namely 3D Double-side Double Type Column detectors, allowing for significant performance enhancement while maintaining a reasonable process complexity, is final ly addressed

RD50: Radiation-hard silicon for HL-LHC trackers

To harvest the maximum physics potential of the LHC , it is foreseen to significantly increase the luminosity by upgrading towards the HL-LHC (High Luminosity LHC). This will mean unprecedented radiation levels, exceeding the LHC fluences tenfold. Due to radiation damage to the silicon sensors presently used, the physics experiments will require new tracking detectors. Within the CERN RD50 Collaboration, a massive R&D; programme is underway across experimental boundaries to develop HL-LHC silicon sensors. One research topic is the connection between the macroscopic sensor properties such as radiation-induced increase of leakage current, doping concentration and trapping, and the microscopic properties. We also study sensors made from p-type silicon bulk, which have a superior radiation hardness as they collect electrons instead of holes, exploiting the lower trapping probability of the electrons and allows for operation in partial depletion. A selection of the latest results achieved within the collaboration on silicon detectors irradiated at levels corresponding to HL-LHC fluences is reported in this paper