The Future of High Powered Electrical Devices

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The Future of High Powered Electrical Devices

• Mpumelelo Richards
• Mary Ellen Zvanut

Research Experience for Undergraduates
Department of Physics
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So whats in the future of electronics?
Silicon Carbide
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But why silicon carbide ?

• Higher temperatures

• High radiation

• High power

These devices will be used in power generation,
automobiles, aircraft, spacecraft, communications
and radar.
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However!
The problem is that
Silicon carbide incurs defects during the growth
process which affect its conductive properties.
These defects number along the order of 1 defect
for 1 x 106 regular Si C bonds.
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Common Defects
Silicon atom
Regular structure
Carbon atom
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Electron Paramagnetic Resonance (EPR)

• To determine the detailed electronic structure
  and symmetry of a point defect
• Detect defects with unpaired electrons

• Zeeman Effect g
  hv/ß B0

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Goals

• Long term goal is to identify defects
  incorporated and correlate them with method of
  growth
• My particular research is focused on using
• electron paramagnetic resonance to
  identify/characterize what is believed to be a
  previously unreported defect.

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Now for the work!
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Data Collection

• Use EPR spectrometer to gather spectra of the
  as-grown samples.

• Determining optimum orientation

• Varying EPR parameters

• Exposing samples to different wavelengths of
  light

AND
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• Sitting in front of the EPR spectrometer for
  hours at a time.

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Annealing

• The samples were annealed at 600 C,800 C,1000
  C, 1200 C ,1400 C,1600 C.

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Simulation Time

• Using EPRMNR computer software the collected
  data was simulated

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What do the simulations tell us?

• We are able to determine the characteristic
  values of the center from the simulation.Namely
• The g-tensor value
• D E values (fine structure constants)
• A- values (nuclei hyperfine constant)

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Integration

• The integral of the data was taken in order to
  find the contributions of the hyperfine Peaks I
  and II.

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Putting it all together1

• The defect that we are observing is not a primary
  contributor to the samples semi-insulating
  property.

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Putting it all together 2An unstudied defect!

• The found characterizing g-tensor, A, d and E
  values do indeed differ from previously reported
  defect values.

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Putting it all together3

• The number of hyperfine lines and their percent
  contributions lead us to search for isotopes with
  nuclei spin ½ and natural abundance near our
  found values.
• After eliminating radioactive isotopes and
  elements highly unlikely to be incorporated
  during the growth process we were left with Si
  and C- an intrinsic defect.

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Conclusions

• The defect is not a primary contributor to the
  SiC semi-insulating properties.
• The defect is believed to be intrinsic.
• We believe it to be a pair defect involving many
  Si and C atoms but the actual arrangement is
  still uncertain.

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Questions?