110 likes | 131 Views
Reciprocal capacitance transients? Tim Gfroerer and Peter Simov Davidson College, Davidson, NC with Mark Wanlass National Renewable Energy Lab, CO ~ Supported by the American Chemical Society – Petroleum Research Fund ~. Quick Outline. Review diode capacitance and the DLTS experiment
E N D
Reciprocal capacitance transients?Tim Gfroerer and Peter SimovDavidson College, Davidson, NCwith Mark WanlassNational Renewable Energy Lab, CO~ Supported by the American Chemical Society – Petroleum Research Fund ~
Quick Outline • Review diode capacitance and the DLTS experiment • Our measurements and an unusual result • A possible explanation and a nice way to test it …
- - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + With Bias - - + + Bias-Dependent Depletion P+ N Depletion Layer
Diode Capacitance d1 No bias Vbuilt-in C = DQ/DV ~ eA/d ENERGY d2 Vbuilt-in+Vapplied Reverse bias Reverse bias increases the separation between the layers where free charge is added or taken away.
- - - - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Depletion Layer With Bias Temporary Reduced Bias Depletion Layer With Bias Temporary Reduced Bias Depletion Layer With Bias - - + + Defect characterization via DLTS P+ N
Computer with LabVIEW (5) Digital Scope(Tektronix) (1) Capacitance meter (Boonton) (2) (4) Oxford 77K Temp Controller (3) Pulse Generator Agilent Cryostat with sample Peter Simov (Davidson ’08) DLTS Experiment
Conclusions • Capacitance transients are non-exponential and rates are incompatible with conventional thermal activation analysis • The reciprocal of the capacitance varies linearly with time, and the slope yields a single thermal activation energy of 0.38eV. Future Work • Thermally-activated reciprocal behavior is a characteristic of hopping transport. • Test dependence on transport distance by varying magnitude of bias pulse.