Correlation of contact resistance with microstructure for Au/Ni/Al/Ti/AlGaN/GaN ohmic contacts using transmission electron microscopy
- 1 March 2001
- journal article
- research article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 89 (6), 3143-3150
- https://doi.org/10.1063/1.1347003
Abstract
Ohmic contacts to AlGaN/GaN heterostructures which have low contact resistance and good surface morphology are required for the development of commercial high power, high frequency transistors in the GaN system. The development of such contacts would be helped by a better understanding of the effect of microstructure on electrical behavior, which is studied here. Au/Ni/Al/Ti/AlGaN/GaN ohmic contact structures were rapid thermal annealed in argon for 60 s at temperatures in the range 550–900 °C. The variation of contact resistance with anneal temperature was correlated with the phase distribution observed by transmission electron microscopy (TEM). A combination of TEM techniques was required to determine the resulting microstructure, including energy filtered TEM, high resolution electron microscopy and energy dispersive x-ray spectrum imaging. Contacts with the lowest resistance were formed after 700 °C annealing. Very little consumption of the 30 nm AlGaN layer was observed. An unidentified phase containing Al, Ti and Au is present at the interface in the samples with low specific contact resistance. The identification of the observed thin interfacial phases (including TiN and AlN) is discussed, along with the effects of oxidation and possible mechanisms of ohmic contact formation.Keywords
This publication has 18 references indexed in Scilit:
- Low resistance Al/Ti/n-GaN ohmic contacts with improved surface morphology and thermal stabilitySemiconductor Science and Technology, 2000
- Long-term thermal stability of Ti/Al/Pt/Au Ohmic contacts to n-type GaNApplied Physics Letters, 2000
- Electric and Morphology Studies of Ohmic Contacts on AlGaN/GaNMRS Proceedings, 2000
- Low resistance ohmic contacts on AlGaN/GaN structures using implantation and the “advancing” Al/Ti metallizationApplied Physics Letters, 1999
- High-transconductance self-aligned AlGaN/GaN modulation-doped field-effect transistors with regrown ohmic contactsApplied Physics Letters, 1998
- Microstructure of Ti/Al ohmic contacts for n-AlGaNApplied Physics Letters, 1998
- Very low resistance ohmic contacts to n-GaNJournal of Electronic Materials, 1998
- Study of contact resistivity, mechanical integrity, and thermal stability of Ti/Al and Ta/Al ohmic contacts to n-type GaNJournal of Electronic Materials, 1998
- The effects of contact size and non-zero metal resistance on the determination of specific contact resistanceSolid-State Electronics, 1982
- About the use of electron energy-loss spectroscopy for chemical mapping of thin foils with high spatial resolutionUltramicroscopy, 1978