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Highly selective photoenhanced wet etching of GaN for defect investigation and device fabrication

Published online by Cambridge University Press:  17 March 2011

P. Visconti ,
M. A. Reshchikov ,
K. M. Jones ,
F. Yun ,
D. F. Wang ,
R. Cingolani ,
H. Morkoç ,
C. W. Litton  and
R. J. Molnar
P. Visconti
Affiliation:
Also with Istituto per lo Studio di Nuovi Materiali per 'Elettronica, CNR, Lecce, 73100, ITALY
M. A. Reshchikov
Affiliation:
Virginia Commonwealth University, Dept. of Electrical Engineering, Richmond, VA, 23284
K. M. Jones
Affiliation:
Virginia Commonwealth University, Dept. of Electrical Engineering, Richmond, VA, 23284
F. Yun
Affiliation:
Virginia Commonwealth University, Dept. of Electrical Engineering, Richmond, VA, 23284
D. F. Wang
Affiliation:
Virginia Commonwealth University, Dept. of Electrical Engineering, Richmond, VA, 23284
R. Cingolani
Affiliation:
Virginia Commonwealth University, Dept. of Electrical Engineering, Richmond, VA, 23284
H. Morkoç
Affiliation:
Virginia Commonwealth University, Dept. of Electrical Engineering, Richmond, VA, 23284
C. W. Litton
Affiliation:
Air Force Research Laboratory, Wright Patterson AFB, OH 45433
R. J. Molnar
Affiliation:
Massachusetts Institute of Technology, Lincoln Laboratory, Lexington, MA, 02420-9108
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Abstract

Photoenhanced electro-chemical (PEC) wet etching has been shown to be suitable for dislocation-density estimation in n-GaN films as well as for GaN-based device fabrication. We report on PEC etching of n-GaN samples grown by MBE and HVPE methods in unstirred aqueous KOH solution under He-Cd laser illumination. Characterization of the etched samples was carried out using atomic force microscopy (AFM) in both cross-sectional and plan-view configurations and scanning electron microscopy (SEM). At moderate illumination densities, the SEM and AFM analyses reveal sub-100 nm scale threading vertical wires on the etched surfaces. The calculated density (∼1×10 9cm−2) is in agreement with dislocation density found by transmission electron microscopy. Using cross-sectional AFM, we find that these vertical wires are ∼1[.proportional]m high and are perpendicular to the sapphire surface. Applying a higher illumination density or an external voltage, we obtain a higher etch rate with a smooth free-feature etched surface. Some highly resistive samples that cannot be etched under normal conditions because the band bending is too small to confine the holes to the surface for them to participate in the PEC process, can be etched with the application of a voltage to the sample. In this case, the etch rate depends on both the polarity and the magnitude of the voltage applied. In an MBE-grown sample with an AlN/GaN superstructure inside, we report on high selectivity between AlN and GaN (AlN is an etch stop); the selectivity is due to the etching mechanism of the PEC process.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 639: Symposium G – GaN and Related Alloys-2000 , 2000 , G3.14
Copyright
Copyright © Materials Research Society 2001

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References

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