Refractory metal-based low-resistance ohmic contacts for submicron GaAs heterostructure devices

Messica, A.; Meirav, U.; Shtrikman, Hadas

doi:10.1016/0040-6090(94)06346-x

Cited by 17 publications

(12 citation statements)

References 27 publications

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“…Our results suggest that for solving this problem the focus should be at maintaining sufficient contact area between Ge-rich Ni grains and the Ge-doped Al x Ga 1−x As layer at long annealing times. This can possibly be engineered by changing the layer thickness, order and composition of the initial AuGe/Ni/Au metalization [19, 12, 14-16, 21, 26], or by including a Pt, Nb or Ag layer below the top Au layer that suppresses the intermixing of this Au with layers at the wafer surface [7,19,15,22,24] (uniform Ni/Ge/As layers have been reported [21]). Alternatively, one can reduce the depth of the 2DEG by etching before deposition of AuGe/Ni/Au (up to the point where this starts to reduce the electron density of the 2DEG).…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…Furthermore, our results now show that the resistance increase for 2DEG samples is also correlated with the expanding AuGa grains below the Ni-rich grains. Various authors have suggested that the increasing contact resistance that is associated with over annealing may be due to a large number of vacancies just below the metal-rich phases near the surface [19,14,24] (but others suggested it was due to excessive in-diffusion of Ni [5,14]). These mainly result from out-diffusion of Ga into the Au-rich grains (which indeed results in a very stable AuGa phase near the original wafer surface [5,16,17]).…”

Section: Summary Of Annealing Mechanismmentioning

confidence: 99%

“…Later studies focused on the formation of an ohmic contact to a 2DEG in a GaAs/Al x Ga 1−x As heterostructure [19][20][21][22][23][24][25][26][27], but do not report how the optimal annealing parameters depend on the depth of the 2DEG below the surface.…”

Section: Introductionmentioning

confidence: 99%

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On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/Al_xGa_1−xAs heterostructures

Koop¹,

Iqbal²,

Limbach³

et al. 2013

Semicond. Sci. Technol.

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On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/AlxGa1-xAs heterostructures Koop On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/AlxGa1-xAs heterostructures. Semiconductor Science and Technology, 28(2), 025006-1-025006-9.[025006]. DOI: 10.1088/0268-1242/28/2/025006 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Abstract Ohmic contacts to a two-dimensional electron gas (2DEG) in GaAs/Al x Ga 1−x As heterostructures are often realized by annealing of AuGe/Ni/Au that is deposited on its surface. We studied how the quality of this type of ohmic contact depends on the annealing time and temperature, and how optimal parameters depend on the depth of the 2DEG below the surface. Combined with transmission electron microscopy and energy-dispersive x-ray spectrometry studies of the annealed contacts, our results allow for identifying the annealing mechanism. We use this for proposing a model that can predict the optimal annealing time when our commonly applied recipe is used for a certain heterostructure at a certain temperature.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Section: Summary Of Annealing Mechanismmentioning

confidence: 99%

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On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/Al_xGa_1−xAs heterostructures

Koop¹,

Iqbal²,

Limbach³

et al. 2013

Semicond. Sci. Technol.

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“…Subsequent studies aimed at improving such contacts and understanding the annealing mechanisms [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Later on, with the increasing importance of the 2DEG in a GaAs/Al x Ga 1−x As heterostructure, research focussed on making ohmic contacts to the buried 2DEG [25][26][27][28][29][30][31][32][33]. Despite these extensive studies, a model was missing that could predict the optimal annealing times and temperatures for different depths of the 2DEG.…”

Section: Introductionmentioning

confidence: 99%

Characterization of low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructure

Iqbal

Reuter

Wieck

et al. 2020

Eur. Phys. J. Appl. Phys.

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The study of electron transport in low-dimensional systems is of importance, not only from a fundamental point of view, but also for future electronic and spintronic devices. In this context heterostructures containing a two-dimensional electron gas (2DEG) are a key technology. In particular GaAs/AlGaAs heterostructures, with a 2DEG at typically 100 nm below the surface, are widely studied. In order to explore electron transport in such systems, low-resistance ohmic contacts are required that connect the 2DEG to macroscopic measurement leads at the surface. Here we report on designing and measuring a dedicated device for unraveling the various resistance contributions in such contacts, which include pristine 2DEG series resistance, the 2DEG resistance under a contact, the contact resistance itself, and the influence of pressing a bonding wire onto a contact. We also report here a recipe for contacts with very low resistance values that remain below 10 Ω for annealing times between 20 and 350 s, hence providing the flexibility to use this method for materials with different 2DEG depths. The type of heating, temperature ramp rate and gas forming used for annealing is found to strongly influence the annealing process and hence the quality of the resulting contacts. *

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“…For application to the drain or source Ohmic contacts of GaN based field effect transistors, morphology is an important concern because it can affect electron beam direct write lithography for the gate Schottky contact [5]. Ti/Al contacts tend to have poor surface morphology because of the high temperature sintering needed to get low contact resistance.…”

Section: Introductionmentioning

confidence: 99%

WSiN cap for Ohmic contacts to n‐GaN with better morphology

Lau

Singh

Gunawan

et al. 2005

phys. stat. sol. (c)

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A WSiN cap can improve the surface morphology of Ti/Al Ohmic contact to n-GaN significantly. This is because it is a conductive diffusion barrier which can help to suppress the decomposition of GaN. With WSiN cap, the edge is much sharper. However, the WSiN film may pick up Ar during the WSiN sputtering process, resulting in some surface morphology problem. This can be solved by lowering the Ar flow rate during sputtering. Auger electron spectroscopy results show that our best WSiN cap has a chemical composition of W 0.62 Si 0.14 N 0.34 .

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Refractory metal-based low-resistance ohmic contacts for submicron GaAs heterostructure devices

Cited by 17 publications

References 27 publications

On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/Al_xGa_1−xAs heterostructures

On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/Al_xGa_1−xAs heterostructures

Characterization of low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructure

WSiN cap for Ohmic contacts to n‐GaN with better morphology

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Refractory metal-based low-resistance ohmic contacts for submicron GaAs heterostructure devices

Cited by 17 publications

References 27 publications

On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/AlxGa1−xAs heterostructures

On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/AlxGa1−xAs heterostructures

Characterization of low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructure

WSiN cap for Ohmic contacts to n‐GaN with better morphology

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Product

Resources

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On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/Al_xGa_1−xAs heterostructures

On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/Al_xGa_1−xAs heterostructures