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Measurement of induced surface charges, contact potentials, and surface states in GaN by electric force microscopy

Bridger, P. M. and Bandić, Z. Z. and Piquette, E. C. and McGill, T. C. (1999) Measurement of induced surface charges, contact potentials, and surface states in GaN by electric force microscopy. Applied Physics Letters, 74 (23). pp. 3522-3524. ISSN 0003-6951. doi:10.1063/1.124148.

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We have studied molecular beam epitaxy grown GaN films of both polarities using electric force microscopy to detect sub 1 µm regions of charge density variations associated with GaN extended defects. The large piezoelectric coefficients of GaN together with strain introduced by crystalline imperfections produce variations in piezoelectrically induced electric fields around these defects. The consequent spatial rearrangement of charges can be detected by electrostatic force microscopy and was found to be on the order of the characteristic Debye length for GaN at our dopant concentration. The electric force microscope signal was also found to be a linear function of the contact potential between the metal coating on the tip and GaN. Electrostatic analysis yielded a surface state density of 9.4 ± 0.5 × 10^10 cm – 2 at an energy of 30 mV above the valence band indicating that the GaN surface is unpinned in this case.

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Additional Information:©1999 American Institute of Physics. (Received 4 March 1999; accepted 12 April 1999) The authors would like to thank E. T. Yu and D. L. Smith for their useful comments and suggestions. This work was supported by DARPA/EPRI and monitored under Grant No. MDA972-98-1-0005.
Subject Keywords:gallium compounds; III-V semiconductors; wide band gap semiconductors; surface states; contact potential; semiconductor epitaxial layers; piezoelectric semiconductors
Issue or Number:23
Record Number:CaltechAUTHORS:BRIapl99
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2456
Deposited By: Archive Administrator
Deposited On:04 Apr 2006
Last Modified:08 Nov 2021 19:48

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