The Microstructure of Ti/Al and TiN Ohmic Contacts to Gallium Nitride

Ruterana, P.; Nouet, G.; Kehagias, Th.; Komninou, Ph.; Karakostas, Th.; Poisson, M.A.; Huet, F.; Morkoç̌, H.

doi:10.1002/(sici)1521-396x(199911)176:1<767::aid-pssa767>3.0.co;2-r

Cited by 21 publications

(16 citation statements)

References 5 publications

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“…Actually, the nucleation and growth of islands occur for short TiN thickness ͑Ͻ1.4 nm͒, which corresponds to islands of 2-3 atomic layers height, suggesting a quasi-2D growth. This is attributed to the very good lattice match ͑mismatch 5.8%͒ between the GaN ͑0001͒ and TiN ͑111͒, which promotes the growth of epitaxial TiN on GaN, [9][10][11] instead of the polycrystalline TiN on Si ͑Refs. 18 and 44͒.…”

Section: A Methods Of Analysismentioning

confidence: 99%

“…In recent years, TiN research has focused on its applications in semiconductor device technology, such as Al diffusion barriers, gate electrodes in fieldeffect transistors and advanced metallizations and interconnects in ultra-large scale integrated circuits and solar cells. [1][2][3][4][5][6][7] In particular, recent studies have shown that TiN is an excellent ohmic contact for the widely studied n-type gallium nitride ͑Si-doped ␣-GaN͒ semiconductor technology, [8][9][10][11] due to its low-work function ͑3.74 eV͒, which is close to the electron affinity of GaN ͑4.1 eV͒. 12 As there is a strong miniaturization trend in microelectronics, smaller device sizes and increased densities demand the development of reliable electronic devices at the nanometer scale.…”

Section: Introductionmentioning

confidence: 99%

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Interface properties and structural evolution of TiN/Si and TiN/GaN heterostructures

Patsalas

Logothetidis

2003

Journal of Applied Physics

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Phonon engineering in nanostructures: Controlling interfacial thermal resistance in multilayer-graphene/dielectric heterojunctions Appl. Phys. Lett. 101, 113111 (2012) Thermally induced interface chemistry in Mo/B4C/Si/B4C multilayered films J. Appl. Phys. 112, 054317 (2012) Enhanced thermal conductivity of polycrystalline aluminum nitride thin films by optimizing the interface structure Spectroscopic ellipsometry ͑SE͒ is employed to study the evolution of microstructure, stoichiometry, and electron-transport properties of titanium nitride ͑TiN͒ heterostructures grown on Si and gallium nitride ͑GaN͒ by reactive magnetron sputtering. In order to achieve subnanometer resolution for the SE analysis, we developed and validated the appropriate methods of interpreting the optical data. Thus, we used ͑a͒ effective medium theories describing the heterostructures in terms of their constituent materials ͑Si, GaN, TiN, over-stoichiometric TiN x , and voids͒, and ͑b͒ a combined Drude-Lorentz model describing the optical response of the conduction and valence electrons of TiN and TiN x . In the case of TiN/Si, the SE results indicate a pure Volmer-Weber type of growth with four distinct growth stages. A TiN x layer is formed before TiN due to the stress variations during growth. On the other hand, TiN/GaN exhibits a quasi two-dimensional growth character. In both cases, the TiN resistivity is very high for films thinner than the critical thickness for homogeneous growth. Thus, for practical applications in electronic devices the thickness of the TiN layer should be at least 4 and 14 nm for TiN/GaN and TiN/Si, respectively.

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Section: A Methods Of Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interface properties and structural evolution of TiN/Si and TiN/GaN heterostructures

Patsalas

Logothetidis

2003

Journal of Applied Physics

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“…A separate series of experiments was performed investigating titanium deposition on GaN(0 0 0 1), where Ti reacts with GaN to form TiN [8,9,15,16]. This reaction has already been observed at room temperature [8].…”

Section: Titanium On Gan(0 0 0 1) -Formation Of Tinmentioning

confidence: 99%

Atomic-scale studies on the growth of palladium and titanium on GaN(0001)

Nörenberg

Castell

2007

Surface Science

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“…6 ͑It should be noted that it is common to list the layers of a multilayer such that the first layer deposited appears first in the contact name, followed by the subsequent layers in the order they were deposited, i.e., Ti is deposited as the first layer and Al the second in a Ti/Al contact.͒ Researchers immediately recognized that this contact offered the first viable solution to the problem of ohmic contacts to n-GaN, which is evidenced by the amount of scrutiny that it received within the first few years to determine why it was so successful. [7][8][9][10] Most subsequent ohmic contacts for this material involve this structure in some way. If annealing temperatures below 800°C are desired, we have found that the best specific contact resistance ( c ) will be obtained when the Ti:Al layer thickness ratio is approximately 1:3.…”

Section: Introductionmentioning

confidence: 99%

Thermally stable, oxidation resistant capping technology for Ti/Al ohmic contacts to n-GaN

Pelto

Chang

Chen

et al. 2002

Journal of Applied Physics

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The intermetallic TiAl 3 has been used as a thermally stable cap for Ti/Al ohmic contacts to n-GaN. The electrical performance of the TiAl 3 -capped contact is nearly the same as that of a standard Ti/Al/Ni/Au contact processed on the same substrate, but the Ti/Al/TiAl 3 contact's performance is optimized at a much lower temperature. The Ti/Al/TiAl 3 contact achieved a lowest specific contact resistance ( c ) of 2.1ϫ10 Ϫ5 ⍀ cm 2 following 1 min at 700°C in flowing, oxygen-gettered ultrahigh purity ͑UHP͒ Ar. The Ti/Al/Ni/Au contact standard achieved a c of 1.8ϫ10 Ϫ5 ⍀ cm 2 following a 15 s anneal at 900°C in flowing, oxygen-gettered UHP Ar. The TiAl 3 -capped contact structure shows little sensitivity to the amount of oxygen in the annealing ambient for optimization, and we found that it could achieve a c of 1.1ϫ10 Ϫ5 ⍀ cm 2 following 5 min at 600°C in air. This performance is almost identical to that attained when the contact was annealed in oxygen-gettered UHP Ar and ordinary Ar. Anneals were extended to a total time of 20 min in the three ambient atmospheres, and the Ti/Al/TiAl 3 contact showed no significant difference in its performance. The fact that this contact structure can withstand optimization anneals in air suggests that it could be annealed alongside a Ni/Au contact to p-GaN in air and still achieve a low contact resistance. The performance of the TiAl 3 -capped bilayer was found to be stable following thermal aging for more than 100 h at 350°C in air, which was also comparable to an optimally annealed Ti/Al/Ni/Au contact aged at the same time. The TiAl 3 material should be an oxidation cap solution for many other Ti/Al contact structures, almost regardless of the Ti:Al layer thickness ratio, since the TiAl 3 will be stable on the upper Al layer. Use of this cap eliminates the need to alter a previously optimized bilayer, thus it is a means of enhancing any existing Ti/Al bilayer contact's performance without necessitating the reoptimization of the layers to accommodate the cap.

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The Microstructure of Ti/Al and TiN Ohmic Contacts to Gallium Nitride

Cited by 21 publications

References 5 publications

Interface properties and structural evolution of TiN/Si and TiN/GaN heterostructures

Interface properties and structural evolution of TiN/Si and TiN/GaN heterostructures

Atomic-scale studies on the growth of palladium and titanium on GaN(0001)

Thermally stable, oxidation resistant capping technology for Ti/Al ohmic contacts to n-GaN

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