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Design, Development, and Testing of a Transient Capacitance Spectroscopy System

Design, Development, and Testing of a Transient Capacitance Spectroscopy System. Presented by: Kiril Simov Special thanks to: Dr. Tim Gfroerer Department of Physics, Davidson College Project supported by the American Chemical Society - Petroleum Research Fund.

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Design, Development, and Testing of a Transient Capacitance Spectroscopy System

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  1. Design, Development, and Testing of a Transient Capacitance Spectroscopy System Presented by: Kiril Simov Special thanks to: Dr. Tim Gfroerer Department of Physics, Davidson College Project supported by the American Chemical Society - Petroleum Research Fund

  2. Motivation: Measuring the Depth of Defect –Related Traps in Semiconductors Pioneers in Measurements of Depth *picture taken from Serway, Raymond A., Beichner, Robert J. and Jewett, John W. Physics for Scientists and Engineers 5th Edition, Saunders College Publishing: Orlandon, FL, 2000

  3. + + + + + + + + + + + + + + + + + + + - - - - - - - - - - + + + + + + + + + + Formation of Depletion Layer (Step 1) + P N

  4. + + + + + + + + + + + + + + + + + + + - - - - - - - - - - + + + + + + + + + + Formation of Depletion Layer (Step 2) Depletion Layer P N

  5. + + + + + + + + + + + + + + + + + + + - - - - - - - - - - + + + + + + + + + + Bias Depletion Layer + Bias Depletion Layer P N Depletion Layer

  6. + + + + + + + + + + + + + + + + + + + - - - - - - - - - - + + + + + + + + + + Depletion Layer + Bias in Equilibrium Depletion Layer P N Bias Depletion Layer

  7. A C = e 0 d Energy diagram in the depletion region Energy d1 V No bias built in(bi) E f d2 V + V bias bi With bias E f

  8. - Carrier Trapping Energy Conductance Band Trap depth Defect Level Valence Band

  9. - - Carrier Escape Low Temperature High Temperature slow fast kT kT

  10. What do we measure? Change in Capacitance Low Temp High Temp time

  11. Instrument Control Loop Computer w/ LabVIEW • Set temperature T • Wait for T to stabilize • Send bias pulse • Measure capacitance C • Obtain C vs. time graph from scope • Next T 1&2 Temperature Controller 3 5 Cryostat and SAMPLE Circuit + Cap. Meter Oscilloscope 4

  12. LabVIEW Control Panel

  13. LabVIEW Diagram

  14. Data Analysis Panel

  15. Conclusions and Future Work • We have developed a versatile Transient Capacitance Spectroscopy (TCS) system using LabVIEW • Accurate TCS spectra have been obtained using test diodes • We will use the system next summer to characterize new devices in collaboration with the National Renewable Energy Laboratory

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