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Defect investigation of GaN thin films etched by photo-electrochemical and hot wet etching by atomic force and transmission electron microscopy

Published online by Cambridge University Press:  21 March 2011

P. Visconti ,
K. M. Jones ,
M. A. Reshchikov ,
R. Cingolani ,
H. Morkoç ,
R. J. Molnar  and
D. J. Smith
P. Visconti
Affiliation:
Also with: Istituto per lo Studio di Nuovi Materiali per l'Elettronica, CNR, 73100, Lecce, ITALY Also with: INFM and Dept. of Innovation Engineering, Univ. of Lecce, 73100, Lecce, ITALY
K. M. Jones
Affiliation:
Virginia Commonwealth University, Dept. of Electrical Engineering, Richmond, VA, 23284
M. A. Reshchikov
Affiliation:
Virginia Commonwealth University, Dept. of Electrical Engineering, Richmond, VA, 23284
R. Cingolani
Affiliation:
Also with: INFM and Dept. of Innovation Engineering, Univ. of Lecce, 73100, Lecce, ITALY
H. Morkoç
Affiliation:
Virginia Commonwealth University, Dept. of Electrical Engineering, Richmond, VA, 23284
R. J. Molnar
Affiliation:
Massachusetts Institute of Technology, Lincoln Laboratory, Lexington, MA 02420-9108
D. J. Smith
Affiliation:
Dept. of Physics and Astronomy and Center for Solid State ScienceArizona State University, Tempe, AZ 85287
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Abstract

The availability of reliable and quick methods to investigate defects in GaN films is of great interest. Photo-electrochemical (PEC), and hot wet etching using both H3PO4 acid and molten KOH have been used to study structural defects in GaN layers grown by hydride vapor phase epitaxy and molecular beam epitaxy. The purpose of this work is to determine whether, and under what conditions, these different methods of investigation are consistent and to get to a more accurate estimation of the defect density. As-grown and etched surfaces were investigated by atomic force microscopy (AFM), and plan-view and cross-sectional transmission electron microscopy (TEM). Free-standing whisker-like features and hexagonal etch pits were formed on the etched sample surfaces by PEC and wet etching, respectively. Using plan-view AFM, we found the density of whiskers (8x108-1×109 cm−2) to be similar to the etch pit densities when etched in both H3PO4 and molten KOH under precise etching conditions. During the wet etching process, a careful balance must be struck to ensure that every defect is delineated, but not overetched to cause merging which would lead to an underestimation of the defect density. Additionally, TEM observations confirmed the dislocation densities obtained by etching, which increased our confidence in the consistency of the methods used.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 680: Symposium E – Wide Bandgap Electronics , 2001 , E5.8
Copyright
Copyright © Materials Research Society 2001

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References

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