Microstructure, electrical properties, and thermal stability of Ti-based ohmic contacts to n-GaN

L. L. Smith; R. F. Davis; R. J. Liu; M. J. Kim; Ray Carpenter

doi:10.1557/JMR.1999.0137

Microstructure, electrical properties, and thermal stability of Ti-based ohmic contacts to n-GaN

L. L. Smith, R. F. Davis, R. J. Liu, M. J. Kim, Ray Carpenter

Chemical Engineering

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

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Abstract

Single Ti layers, single TiN layers, and thin Ti films overlayered with Au were investigated as ohmic contacts to n-type (n = 4.5 × 10¹⁷ to 7.4 × 10¹⁸ cm^-3) single-crystal GaN (0001) films. Transmission line measurements (TLM) revealed the as-deposited TiN and Au/Ti contacts on n = 1.2 × 10¹⁸ cm^-3 to be ohmic with room-temperature specific contact resistivities of 650 and 2.5 × 10^-5 Ω cm², respectively. Single Ti layer contacts had high resistance and were weakly rectifying in the as-deposited condition. The three contact/GaN systems exhibited a substantial decrease in resistivity after annealing; the value of ρ_c was also a function of the carrier concentration in the GaN. The Au/Ti contacts exhibited the lowest resistivity values yet observed in these contact studies, particularly for the more lightly doped n-GaN. The ρ_c for n = 1.2 × 10¹⁸ cm^-3 reached 1.2 × 10^-6 Ω cm²; for n = 4.5 × 10¹⁷ cm^-3, ρ_c = 7.5 × 10^-5 Ω cm² after annealing both samples through 900 (Service mark)C. X-ray photoelectron spectroscopy (XPS) and high-resolution cross-sectional transmission electron microscopy (X-TEM) analysis revealed the formation of TiN at the interface of annealed Ti layers in contact with GaN, which is believed to be beneficial for ohmic contact performance on n-GaN.

Original language	English (US)
Pages (from-to)	1032-1038
Number of pages	7
Journal	Journal of Materials Research
Volume	14
Issue number	3
DOIs	https://doi.org/10.1557/JMR.1999.0137
State	Published - Mar 1999

ASJC Scopus subject areas

General Materials Science
Condensed Matter Physics
Mechanics of Materials
Mechanical Engineering

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@article{91b10412c15140ef9c6f12e9ecd08cf8,

title = "Microstructure, electrical properties, and thermal stability of Ti-based ohmic contacts to n-GaN",

abstract = "Single Ti layers, single TiN layers, and thin Ti films overlayered with Au were investigated as ohmic contacts to n-type (n = 4.5 × 1017 to 7.4 × 1018 cm-3) single-crystal GaN (0001) films. Transmission line measurements (TLM) revealed the as-deposited TiN and Au/Ti contacts on n = 1.2 × 1018 cm-3 to be ohmic with room-temperature specific contact resistivities of 650 and 2.5 × 10-5 Ω cm2, respectively. Single Ti layer contacts had high resistance and were weakly rectifying in the as-deposited condition. The three contact/GaN systems exhibited a substantial decrease in resistivity after annealing; the value of ρc was also a function of the carrier concentration in the GaN. The Au/Ti contacts exhibited the lowest resistivity values yet observed in these contact studies, particularly for the more lightly doped n-GaN. The ρc for n = 1.2 × 1018 cm-3 reached 1.2 × 10-6 Ω cm2; for n = 4.5 × 1017 cm-3, ρc = 7.5 × 10-5 Ω cm2 after annealing both samples through 900 (Service mark)C. X-ray photoelectron spectroscopy (XPS) and high-resolution cross-sectional transmission electron microscopy (X-TEM) analysis revealed the formation of TiN at the interface of annealed Ti layers in contact with GaN, which is believed to be beneficial for ohmic contact performance on n-GaN.",

author = "Smith, {L. L.} and Davis, {R. F.} and Liu, {R. J.} and Kim, {M. J.} and Ray Carpenter",

note = "Funding Information: The authors express their thanks for the assistance of E. P. Carlson and M. D. Bremser (NCSU) for helpful discussions and the growth of the GaN samples, and to Cree Research for supplying the SiC wafers for this work. This work was supported by the Office of Naval Research under Contract No. N00014-92-J-1720 (NCSU) with Colin Wood as the technical monitor, and the U.S. Department of Energy under Grant No. DE-FG03-94ER45510 (Dr. O. Buck) (ASU). R. Davis was partially supported via the Kobe Steel, Ltd. Professorship.",

year = "1999",

month = mar,

doi = "10.1557/JMR.1999.0137",

language = "English (US)",

volume = "14",

pages = "1032--1038",

journal = "Journal of Materials Research",

issn = "0884-2914",

publisher = "Materials Research Society",

number = "3",

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T1 - Microstructure, electrical properties, and thermal stability of Ti-based ohmic contacts to n-GaN

AU - Smith, L. L.

AU - Davis, R. F.

AU - Liu, R. J.

AU - Kim, M. J.

AU - Carpenter, Ray

N1 - Funding Information: The authors express their thanks for the assistance of E. P. Carlson and M. D. Bremser (NCSU) for helpful discussions and the growth of the GaN samples, and to Cree Research for supplying the SiC wafers for this work. This work was supported by the Office of Naval Research under Contract No. N00014-92-J-1720 (NCSU) with Colin Wood as the technical monitor, and the U.S. Department of Energy under Grant No. DE-FG03-94ER45510 (Dr. O. Buck) (ASU). R. Davis was partially supported via the Kobe Steel, Ltd. Professorship.

PY - 1999/3

Y1 - 1999/3

N2 - Single Ti layers, single TiN layers, and thin Ti films overlayered with Au were investigated as ohmic contacts to n-type (n = 4.5 × 1017 to 7.4 × 1018 cm-3) single-crystal GaN (0001) films. Transmission line measurements (TLM) revealed the as-deposited TiN and Au/Ti contacts on n = 1.2 × 1018 cm-3 to be ohmic with room-temperature specific contact resistivities of 650 and 2.5 × 10-5 Ω cm2, respectively. Single Ti layer contacts had high resistance and were weakly rectifying in the as-deposited condition. The three contact/GaN systems exhibited a substantial decrease in resistivity after annealing; the value of ρc was also a function of the carrier concentration in the GaN. The Au/Ti contacts exhibited the lowest resistivity values yet observed in these contact studies, particularly for the more lightly doped n-GaN. The ρc for n = 1.2 × 1018 cm-3 reached 1.2 × 10-6 Ω cm2; for n = 4.5 × 1017 cm-3, ρc = 7.5 × 10-5 Ω cm2 after annealing both samples through 900 (Service mark)C. X-ray photoelectron spectroscopy (XPS) and high-resolution cross-sectional transmission electron microscopy (X-TEM) analysis revealed the formation of TiN at the interface of annealed Ti layers in contact with GaN, which is believed to be beneficial for ohmic contact performance on n-GaN.

AB - Single Ti layers, single TiN layers, and thin Ti films overlayered with Au were investigated as ohmic contacts to n-type (n = 4.5 × 1017 to 7.4 × 1018 cm-3) single-crystal GaN (0001) films. Transmission line measurements (TLM) revealed the as-deposited TiN and Au/Ti contacts on n = 1.2 × 1018 cm-3 to be ohmic with room-temperature specific contact resistivities of 650 and 2.5 × 10-5 Ω cm2, respectively. Single Ti layer contacts had high resistance and were weakly rectifying in the as-deposited condition. The three contact/GaN systems exhibited a substantial decrease in resistivity after annealing; the value of ρc was also a function of the carrier concentration in the GaN. The Au/Ti contacts exhibited the lowest resistivity values yet observed in these contact studies, particularly for the more lightly doped n-GaN. The ρc for n = 1.2 × 1018 cm-3 reached 1.2 × 10-6 Ω cm2; for n = 4.5 × 1017 cm-3, ρc = 7.5 × 10-5 Ω cm2 after annealing both samples through 900 (Service mark)C. X-ray photoelectron spectroscopy (XPS) and high-resolution cross-sectional transmission electron microscopy (X-TEM) analysis revealed the formation of TiN at the interface of annealed Ti layers in contact with GaN, which is believed to be beneficial for ohmic contact performance on n-GaN.

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JO - Journal of Materials Research

JF - Journal of Materials Research

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Microstructure, electrical properties, and thermal stability of Ti-based ohmic contacts to n-GaN

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