Microstructure of Ti/Al/Ni/Au ohmic contacts for N-polar GaN/AlGaN high electron mobility transistor devices

Lin Zhou; Michael R. Johnson; David Smith; David J. Meyer; David F. Storm; Douglas Scott Katzer; Brian P. Downey

doi:10.1116/1.4829878

Microstructure of Ti/Al/Ni/Au ohmic contacts for N-polar GaN/AlGaN high electron mobility transistor devices

Lin Zhou, Michael R. Johnson, David Smith, David J. Meyer, David F. Storm, Douglas Scott Katzer, Brian P. Downey

Research output: Contribution to journal › Article › peer-review

9 Scopus citations

Abstract

The microstructure of Ti/Al/Ni/Au ohmic contacts on N-polar GaN/AlGaN high electron mobility transistor heterostructures annealed from 800 °C to 900 °C has been studied using transmission electron microscopy and associated analytical techniques. Two ohmic metal stacks with different Ti/Al/Ni/Au layer thicknesses (20/200/40/50 nm and 20/100/10/50 nm) have been examined. Samples with low ohmic contact resistance after annealing were found to have two common characteristics: (1) the top GaN channel layer had completely reacted with Ti metal to form a polycrystalline TiN layer and (2) a ∼5 nm-thick Au-rich layer was present near the TiN/AlGaN interface. Possible conduction mechanisms related to the presence of Au in low ohmic contact resistance samples are discussed.

Original language	English (US)
Article number	011201
Journal	Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics
Volume	32
Issue number	1
DOIs	https://doi.org/10.1116/1.4829878
State	Published - Jan 1 2014

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Instrumentation
Process Chemistry and Technology
Surfaces, Coatings and Films
Electrical and Electronic Engineering
Materials Chemistry

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title = "Microstructure of Ti/Al/Ni/Au ohmic contacts for N-polar GaN/AlGaN high electron mobility transistor devices",

abstract = "The microstructure of Ti/Al/Ni/Au ohmic contacts on N-polar GaN/AlGaN high electron mobility transistor heterostructures annealed from 800 °C to 900 °C has been studied using transmission electron microscopy and associated analytical techniques. Two ohmic metal stacks with different Ti/Al/Ni/Au layer thicknesses (20/200/40/50 nm and 20/100/10/50 nm) have been examined. Samples with low ohmic contact resistance after annealing were found to have two common characteristics: (1) the top GaN channel layer had completely reacted with Ti metal to form a polycrystalline TiN layer and (2) a ∼5 nm-thick Au-rich layer was present near the TiN/AlGaN interface. Possible conduction mechanisms related to the presence of Au in low ohmic contact resistance samples are discussed.",

author = "Lin Zhou and Johnson, {Michael R.} and David Smith and Meyer, {David J.} and Storm, {David F.} and {Scott Katzer}, Douglas and Downey, {Brian P.}",

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T1 - Microstructure of Ti/Al/Ni/Au ohmic contacts for N-polar GaN/AlGaN high electron mobility transistor devices

AU - Zhou, Lin

AU - Johnson, Michael R.

AU - Smith, David

AU - Meyer, David J.

AU - Storm, David F.

AU - Scott Katzer, Douglas

AU - Downey, Brian P.

PY - 2014/1/1

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N2 - The microstructure of Ti/Al/Ni/Au ohmic contacts on N-polar GaN/AlGaN high electron mobility transistor heterostructures annealed from 800 °C to 900 °C has been studied using transmission electron microscopy and associated analytical techniques. Two ohmic metal stacks with different Ti/Al/Ni/Au layer thicknesses (20/200/40/50 nm and 20/100/10/50 nm) have been examined. Samples with low ohmic contact resistance after annealing were found to have two common characteristics: (1) the top GaN channel layer had completely reacted with Ti metal to form a polycrystalline TiN layer and (2) a ∼5 nm-thick Au-rich layer was present near the TiN/AlGaN interface. Possible conduction mechanisms related to the presence of Au in low ohmic contact resistance samples are discussed.

AB - The microstructure of Ti/Al/Ni/Au ohmic contacts on N-polar GaN/AlGaN high electron mobility transistor heterostructures annealed from 800 °C to 900 °C has been studied using transmission electron microscopy and associated analytical techniques. Two ohmic metal stacks with different Ti/Al/Ni/Au layer thicknesses (20/200/40/50 nm and 20/100/10/50 nm) have been examined. Samples with low ohmic contact resistance after annealing were found to have two common characteristics: (1) the top GaN channel layer had completely reacted with Ti metal to form a polycrystalline TiN layer and (2) a ∼5 nm-thick Au-rich layer was present near the TiN/AlGaN interface. Possible conduction mechanisms related to the presence of Au in low ohmic contact resistance samples are discussed.

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Microstructure of Ti/Al/Ni/Au ohmic contacts for N-polar GaN/AlGaN high electron mobility transistor devices

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