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Proceedings Paper

Investigation of charge trapping at the oxide/semiconductor interface for MBE-grown GaN films
Author(s): J. C. Moore; M. A. Reshchikov; J. E. Ortiz; J. Xie; H. Morkoç; A. A. Baski
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Paper Abstract

Charge trapping resulting in localized band bending on MBE-grown GaN films was investigated using a new combination of conducting atomic force microscopy (CAFM) and scanning Kelvin probe microscopy (SKPM). CAFM was first used to locally inject charge at the surface oxide/semiconductor interface, and then SKPM was performed to monitor the evolution of the resulting surface potential. In a dark environment, the additionally charged interface states due to CAFM charge injection resulted in an induced additional band bending that persisted for hours. The induced band bending is nominal (<0.5 eV) for CAFM voltages less than 8 V, and reaches a saturation value of ~3 eV for voltages greater than 10 V. The saturation band bending corresponds to a total density of charged interface states (2×1012 cm-2) that is double the value observed for the intrinsic surface. Induced band bending could still be observed up to 4 h after charge injection, indicating that charge trapping is relatively stable in a dark environment. However, charged interface states could be rapidly neutralized by illumination with UV light. A phenomenological model based on a tunneling mechanism was used to successfully describe the CAFM charge injection, where electrons travel from the tip through an oxide barrier and become trapped at oxide/GaN interface states. Saturation occurs due to the existence of a finite density of chargeable states at the interface. After charge injection, the decrease in induced band bending with time was found to be consistent with a thermionic model of charge transfer from the interface to the bulk.

Paper Details

Date Published: 15 February 2008
PDF: 9 pages
Proc. SPIE 6894, Gallium Nitride Materials and Devices III, 68940B (15 February 2008); doi: 10.1117/12.768041
Show Author Affiliations
J. C. Moore, Longwood Univ. (United States)
M. A. Reshchikov, Virginia Commonwealth Univ. (United States)
J. E. Ortiz, Virginia Commonwealth Univ. (United States)
J. Xie, Virginia Commonwealth Univ. (United States)
H. Morkoç, Virginia Commonwealth Univ. (United States)
A. A. Baski, Virginia Commonwealth Univ. (United States)


Published in SPIE Proceedings Vol. 6894:
Gallium Nitride Materials and Devices III
Hadis Morkoç; Cole W. Litton; Jen-Inn Chyi; Yasushi Nanishi; Euijoon Yoon, Editor(s)

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