Nonalloyed ohmic contact formation in Ti/Al contacts to n-type AlGaN

Lin, Yow Jon; Chien, Feng-Tso; Lee, Ching-Ting; Lin, Chi Shin; Liu, Yang Chun

doi:10.1088/0022-3727/41/17/175105

Cited by 4 publications

(7 citation statements)

References 25 publications

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“…In this study, the Ni layer was designed to produce high reflectance because it has higher reflectance along with high work function than Ag. On the other hand, the Ag layer was used to reduce contact resistivity by increasing acceptors near the AlGaN surface region, [34][35][36] as will be discussed later (Fig. 8).…”

Section: Resultsmentioning

confidence: 99%

“…This means that annealing caused the surface Fermi level to be shifted to the valence-band edge. 34,35,37 The formation of an Ag-Ga solid solution at the Ag/p-AlGaN interface after annealing 500 °C leads to the occurrence of acceptor-like Ga vacancies at the AlGaN surface region, 36,38,39 which can be responsible for the binding energy shift 34,35,37 and consequently reduce the Schottky barrier height at the Ag/p-AlGaN interface. This is also true for the Ni/Au-based contacts (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Optimization of Ni/Ag-Based Reflectors to Improve the Performance of 273 nm Deep Ultraviolet AlGaN-Based Light Emitting Diodes

Sim

Kim

Lee

et al. 2021

ECS J. Solid State Sci. Technol.

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We optimized Ni/Ag-based p-type reflectors for the improvement of efficiency of 273 nm deep ultraviolet (DUV) AlGaN-based flip-chip light emitting diodes (FCLEDs). The Ni(3 nm)/Ag(5–15 nm)/Al/Ni and Ni(25–50 nm)/Ag/Ni contacts exhibited higher reflectance (36.4–39.5%) at 273 nm than reference Ni(5 nm)/Au(5 nm)/Al/Ni contact (26.1%). The Ni(3 nm)/Ag/Al(200 nm)/Ni(20 nm) and Ni/Ag(200 nm)/Ni(20 nm)-based FCLEDs gave forward voltages in the rage of 6.93–7.11 V and 5.5–6.28 V at 20 mA, respectively, whereas the Ni/Au-based sample showed 6.35 V. Further, the Ni(3 nm)/Ag(10 nm)/Al/Ni-based and Ni(50 nm)/Ag(200 nm)/Ni-based samples exhibited 4.85% and 13.4% larger output power at 1.2 W than the reference sample. The Ni(3 nm)/Ag(10 nm)-based and Ni(50 nm)/Ag(200 nm)/Ni-based samples produced 5.6% and 8.5% higher peak external quantum efficiency than the reference sample. It was further shown that the Ni(3 nm)/Ag(10 nm)/Al/Ni-based and Ni(50 nm)/Ag(200 nm)/Ni-based samples experienced less efficiency droop (namely, 27.9 and 26.4%, respectively) than the reference sample (31.4%). Based on the scanning transmission electron microscopy and X-ray photoemission spectroscopy results, the ohmic formation mechanism is described and discussed.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Optimization of Ni/Ag-Based Reflectors to Improve the Performance of 273 nm Deep Ultraviolet AlGaN-Based Light Emitting Diodes

Sim

Kim

Lee

et al. 2021

ECS J. Solid State Sci. Technol.

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“…Based on the above experimental result, we can conclude that, as increases from 10.0 nm to 80.0 nm, the average size of the magnetic domains in the films goes up and the direction of the magnetization of the samples deviate from the in-plane reorientation gradually with the increase of the domain size. Since the direction of the tip magnetization is normal to the film surface, which is taken as the direction, the oscillation phase shift ∆ recorded as the magnetic force image is approximately represented by [2] ∆ ≈ − ,…”

Section: -2mentioning

confidence: 99%

“…It has also been shown that, because of the surface roughness of the film, the spins are easily pinned at 117501-3 the terraces or craters. [2] As a result, the magnetization fluctuation produces a rather inhomogeneous field along the domain walls. From the energy minimization point of view, the irregular magnetic domain structure should be dominated by the balance between the shape anisotropy and surface anisotropy of the film and then reduce the total free energy of the system.…”

Section: -2mentioning

confidence: 99%

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Microstructure and Magnetic Domains of Iron Films on Liquid Surfaces

Xie¹,

Xia²,

Zhang³

et al. 2009

Chinese Phys. Lett.

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Iron (Fe) films with a thickness ranging from 1.0 nm to 80.0 nm are deposited on silicone oil surfaces by a vapor phase deposition method. The films with a thickness of < 2.0 nm do not exhibit planar morphology but ramified aggregates instead. Magnetic force microscopy studies for the Fe films (10.0 nm ≤ ≤ 80.0 nm) show that the domain wall structure is widespread and irregularly shaped and the oscillation phase shift Δ , which records as the magnetic force image, changes from 0.29 ∘ to 0.81 ∘. Correspondingly, the magnetic force gradient varies from 1.4 × 10 −3 to 4.0 × 10 −3 N/m, respectively. In our measurement, the characteristic domain walls, such as Bloch walls, Néel walls and cross-tie walls, are not observed in the film system clearly.

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Thermal stability study of gallium nitride based magnetic field sensor

Shetty,

Kuchuk,

Zamani-Alavijeh

et al. 2023

Journal of Applied Physics

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We investigated the thermal stability and performance of AlGaN/AlN/GaN Hall-effect sensors under industry-relevant atmospheric conditions. The thermal stability and performance of Hall sensors are evaluated by monitoring Hall sensitivity, two-dimensional electron gas density, and Ohmic contact resistance during aging at 200 °C for up to 2800 h under atmospheric conditions. This was accomplished by characterizing AlGaN/AlN/GaN micro-Hall sensors, with and without contacts, and before and after being placed under different thermal aging times. Observed electrical performance was correlated with the micro-structural evolution of AlGaN/AlN/GaN Hall sensor heterostructures. Results indicate that the AlGaN/AlN/GaN Hall sensor provides stable performance for as long as 2800 h aging at 200 °C without any significant degradation of (i) Hall sensitivity, (ii) two-dimensional electron gas, and (iii) Ohmic contacts. However, there was a small change in sheet density and mobility, which is due to a decrease in polarization, resulting from local inhomogeneous strain relief at the barrier layer. During the early stage of thermal aging, a decrease in contact resistance was also observed and attributed to (i) out-diffusion of “Ga” at the vicinity of the contact interface, and (ii) a reduction in oxygen concentration and formation of Al–Ti intermediate alloy at the GaN/Ti interface, resulting in a reduced barrier and enhanced electron transport at the contacts. However, despite these small changes, results indicate that the AlGaN/AlN/GaN Hall sensor provides stable performance for as long as 2800 h thermal aging at 200 °C.

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Nonalloyed ohmic contact formation in Ti/Al contacts to n-type AlGaN

Cited by 4 publications

References 25 publications

Optimization of Ni/Ag-Based Reflectors to Improve the Performance of 273 nm Deep Ultraviolet AlGaN-Based Light Emitting Diodes

Optimization of Ni/Ag-Based Reflectors to Improve the Performance of 273 nm Deep Ultraviolet AlGaN-Based Light Emitting Diodes

Microstructure and Magnetic Domains of Iron Films on Liquid Surfaces

Thermal stability study of gallium nitride based magnetic field sensor

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