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TEM assessment of GaN/AlGaN/TiAlTiAu and GaN/AlGaN/TiAlPdAu ohmic contacts

Published online by Cambridge University Press:  21 March 2011

M W Fay
Affiliation:
School of Mechanical, Materials, Manufacturing Engineering and Management, University of Nottingham, University Park, Nottingham NG7 RD, UK
G Moldovan
Affiliation:
School of Mechanical, Materials, Manufacturing Engineering and Management, University of Nottingham, University Park, Nottingham NG7 RD, UK
I Harrison
Affiliation:
School of Electrical and Electronic Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK
J C Birbeck
Affiliation:
QinetiQ Ltd, St Andrews Rd, Malvern, Worcs WR14 3PS, UK
B T Hughes
Affiliation:
QinetiQ Ltd, St Andrews Rd, Malvern, Worcs WR14 3PS, UK
M J Uren
Affiliation:
QinetiQ Ltd, St Andrews Rd, Malvern, Worcs WR14 3PS, UK
T Martin
Affiliation:
QinetiQ Ltd, St Andrews Rd, Malvern, Worcs WR14 3PS, UK
P D Brown
Affiliation:
School of Mechanical, Materials, Manufacturing Engineering and Management, University of Nottingham, University Park, Nottingham NG7 RD, UK
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Abstract

TiAlTiAu and TiAlPdAu contacts to GaN/AlGaN, rapid thermal annealed at temperatures ranging from 650°C to 950°C, have been investigated using conventional and chemical TEM analysis. Ohmic behaviour was seen for TiAlTiAu contacts annealed at 750°C or higher, but was not observed in TiAlPdAu contacts annealed at up to 950°C. The effect of annealing temperature on the structural evolution of the contact is explained in terms of different extents of interfacial reaction. In particular, the formation of TiN after anneals at high temperatures is required to activate the contact. At anneals of 950°C, TiAlTiAu samples show a structure of TiN grains within an interfacial band, with TiN inclusions into the AlGaN preceded by an Al-Au diffusion front. Inclusion formation and the effect on the contact electrical performance is described.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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