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23 April 2001 Measurement of carrier transport and dynamics in wide bandgap semiconductors using femtosecond pump-probe techniques
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Proceedings Volume 4280, Ultrafast Phenomena in Semiconductors V; (2001)
Event: Symposium on Integrated Optics, 2001, San Jose, CA, United States
We present an optically-detected time-of-flight technique with femtosecond resolution that monitors the change in the electroabsorption due to charge transport in a p-i-n diode, and show how it may be used to determine the electron transit time, velocity overshoot, and velocity-field characteristic in GaN at room temperature. In a GaN homojunction p-i-n diode, the transit time drops with increasing electric field E in the intermediate field regime (50 - 100 kV/cm), and the electron velocity possesses a weak, quasi-linear dependence on E attributed to polar optical phonon scattering. In the high field regime the transit time and the electron velocity gradually become independent of E. The peak electron velocity of 1.9 X 107 cm/s, corresponding to a transit time of approximately 2.5 ps across the 0.53 micrometers depletion region, is attained at approximately 225 kV/cm. The experimental results are in qualitative agreement with theoretical steady-state velocity-field characteristics found in the literature. A measurement of the high field (approximately 300 kV/cm) transient electron velocity overshoot was also performed using a semi-transparent p-contact AlGaN/GaN heterojunction p-i-n diode. The peak electron velocity of 6.25 X 107 cm/s attained within the first 200 fs decays within 1 ps to a steady-state velocity of 3.2 X 107 cm/s in this improved device.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael Wraback, Hongen Shen, M. C. Wood, John C. Carrano, Charles J. Collins, Ting Li, Joe C. Campbell, Christopher J. Eiting, Damien J. H. Lambert, U. Chowdhury, M. M. Wong, Russell D. Dupuis, Matthew J. Schurman, and Ian T. Ferguson "Measurement of carrier transport and dynamics in wide bandgap semiconductors using femtosecond pump-probe techniques", Proc. SPIE 4280, Ultrafast Phenomena in Semiconductors V, (23 April 2001);

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