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Electrical, structural and microstructural characteristics of as-deposited and annealed Pt and Au contacts on chemical-vapor-cleaned GaN thin films

Authors :
David J. Smith
Marlene Albrecht
Robert J. Nemanich
Kieran Mark Tracy
Robert F. Davis
P. Q. Miraglia
H. Mclean
Edward A. Preble
Sharon Kiesel
Source :
Journal of Applied Physics. 91:2133-2137
Publication Year :
2002
Publisher :
AIP Publishing, 2002.

Abstract

Schottky contacts of Pt(111) and Au(111) were deposited on chemical-vapor-cleaned, n-type GaN(0001) thin films. The growth mode of the deposition, as determined by x-ray photoelectron spectroscopy analysis, followed the two-dimensional Frank–van der Merwe growth model. The resulting as-deposited metal films were monocrystalline and epitaxial with a (111)//(0002) relationship with the GaN. Selected samples were annealed for three minutes at 400 °C, 600 °C or 800 °C. The rectifying behavior of both contacts degraded at 400 °C; they became ohmic after annealing at 600 °C (Au) or 800 °C (Pt). High-resolution transmission electron micrographs revealed reactions at the metal/GaN interfaces for the higher temperature samples. X-ray diffraction results revealed an unidentified phase in the Pt sample annealed at 800 °C. A decrease in the room temperature in-plane (111) lattice constant for both metals, ranging from −0.1% to −0.5%, was observed as the annealing temperature was increased from 400 to 800 °C. This plastic deformation was caused by tensile stresses along the [111] direction that exceeded the yield strength as a result of the large differences in the coefficients of thermal expansion between the metal contacts and the GaN film.

Details

ISSN :
10897550 and 00218979
Volume :
91
Database :
OpenAIRE
Journal :
Journal of Applied Physics
Accession number :
edsair.doi...........7597061de9ffc82df010aabfde71ab19