Transcript Deep Level Transient Spectroscopy (DLTS)

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
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
Formation of Depletion Layer (Step 1)
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Formation of Depletion Layer (Step 2)
Depletion Layer
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Depletion Layer + Bias
Depletion Layer
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Depletion Layer
Bias
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Depletion Layer + Bias in Equilibrium
Depletion Layer
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Depletion Layer
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Bias
Energy diagram in the depletion region
Energy
No
bias
With
bias
Carrier Trapping
Energy
Conductance Band
Trap depth
Defect Level
Valence Band
Carrier Escape
Low Temperature
High Temperature
slow
fast
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kT
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kT
Change in Capacitance
What do we measure?
Low Temp
High Temp
time
Instrument Control Loop
1&2
Temperature
Controller
Computer w/
LabVIEW
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5
Cryostat and
SAMPLE
Circuit + Cap.
Meter
1.
Set temperature T
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Wait for T to stabilize
3.
Send bias pulse
4.
Measure capacitance C
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Obtain C vs. time
graph from scope
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Next T
Oscilloscope
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LabVIEW Control Panel
LabVIEW Diagram
Data Analysis Panel
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