Low-temperature sintered AuGe/GaAs ohmic contact

Aina, O.; Katz, W.; Baliga, B. J.; Rose, Kenneth

doi:10.1063/1.329989

Cited by 31 publications

(3 citation statements)

References 10 publications

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“…To explain the ohmic behavior of the contact a heavily G e -d o p e d S c h o t t k y barrier is a s s u m e d according to the classical model (14). Although no direct evidence can be given, several arguments strongly support this assump-tion: The first is an experimental result obtained by Aina et al (15) for Au:Ge contacts. These authors investigated the contact metal to substrate interaction after a similar heat-treatment and found Ge indiffusion applying SIMS analysis.…”

Section: Discussionmentioning

confidence: 94%

Very Stable Ge/Au/Cr/Au Ohmic Contacts to GaAs

Willer

Ristow

Kellner

et al. 1988

J. Electrochem. Soc.

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The electrical and metallurgical annealing properties of Ge/Au/Cr/Au contacts have been studied on samples with different implantation doses. Especially the contacts with higher doses exhibit excellent thermal stability with low specific transfer resistance pt = 95 12~m. When they were annealed at 390~ for 128h, p~ was still as low as 140 t2~m. TEM cross sections of samples analyzed after a heat-treatment of 390~ revealed a smooth surface morphology and a smooth interface of the contact metal with the GaAs substrate. Taking into account thermochemical arguments the high thermal stability is attributed to the Au(Ga) solid solution formed during the alloying reaction. Current is found to flow from these Au(Ga) grains to the heavily Ge doped semiconductor interface via a tunneling mechanism according to the classical model. While the spreading resistance model is not applicable to the system under study the recent model of Dingfen et al.

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Section: Discussionmentioning

confidence: 94%

Very Stable Ge/Au/Cr/Au Ohmic Contacts to GaAs

Willer

Ristow

Kellner

et al. 1988

J. Electrochem. Soc.

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“…In addition, lateral Au diffusion on the GaAs surface was observed [38±40], which limited applicability of these contacts to advanced GaAs devices with reduced dimensions. Several improvements in the surface morphology were achieved without changing AuGe metallization: the surface morphology was slightly improved by decreasing the annealing temperature [41,42] or by reducing the annealing time as short as microseconds by laser annealing [43±48]. However, the thermal instability of the electrical properties during subsequent annealing after contact formation [34], and the large spread of the contact resistances on a given wafer could not be improved.…”

Section: Brief History Of Development Of Augeni Ohmic Contact Materialsmentioning

confidence: 99%

Development of refractory ohmic contact materials for gallium arsenide compound semiconductors

Murakami

2002

Science and Technology of Advanced Materials

239

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Recent strong demands for optoelectronic communication and portable telephones have encouraged engineers to develop optoelectronic devices, microwave devices, and high-speed devices using hetero-structural GaAs-based compound semiconductors. Although the GaAs crystal growth techniques had reached a level to control the compositional stoichiometry and crystal defects on a nearly atomic scale by the advanced techniques such as molecular beam epitaxy and metal organic chemical vapor deposition techniques, development of ohmic contact materials (which play a key role to inject external electric current from the metals to the semiconductors) was still on a trial-and-error basis. Our research efforts have been focused to develop low resistance, refractory ohmic contact materials to n-type GaAs using the deposition and annealing techniques, and it was found the growth of homo-or hetero-epitaxial intermediate semiconductor layers (ISL) on the GaAs surface was essential for the low resistance ohmic contact formation. In this paper, two typical examples of ohmic contact materials developed by forming ISL were given. The one was refractory NiGe-based ohmic contact material, which was developed by forming the homo-epitaxial ISL doped heavily with donors. This heavily doped ISL was discovered to be formed through the regrowth mechanism of GaAs layers at the NiGe/GaAs interfaces during annealing at elevated temperatures. To reduce the contact resistance further down to a value required by the device designers, an addition of small amounts of third elements to NiGe, which have strong binding energy with Ga, was found to be essential. These third elements contributed to increase the carrier concentration in ISL. The low resistance ohmic contact materials developed by forming homo-epitaxial ISL were Ni/M/Ge where a slash`/' denotes the deposition sequence and M is an extremely thin (,5 nm) layer of Au, Ag, Pd, Pt or In. The other was refractory In x Ga 12x As-based ohmic contact materials which were developed by forming the hetero-epitaxial ISL with low Schottky barrier to the contacting metals by growing the In x Ga 12x As layers on the GaAs substrate by sputter-depositing In x Ga 12x As targets and subsequently annealing at elevated temperatures. To reduce the contact resistance, it was found that this In x Ga 12x As (ISL) layer had to have In compositional gradient normal to the GaAs surface: the In concentration being rich at the metal/In x Ga 12x As interface and poor close to the In x Ga 12x As/GaAs interface. This concentration graded ISL reduced both the barrier heights at the metal/ISL and ISL/GaAs interfaces and reduced the contact resistance. The ohmic contact materials developed by forming heteroepitaxial ISL was In 0.7 Ga 0.3 As/Ni/WN 2 /W. These contact materials formed refractory compounds at the interfaces, which was also found to be essential to improve thermal stability of ohmic contacts used in the GaAs devices.

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“…Ni is added into the alloy as a wetting agent. The low surface tension of Ni helps to prevent the AuGe metal from "balling-up" during alloying and to improve the contact adherence [15]. Au enhances the out-diffusion of Ga, resulting in Ge substituting Ga sites, which produces the desired highly doped n -GaAs layer.…”

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confidence: 99%

Optimization of AuGe-Ni_Au ohmic contacts for GaAs MOSFETs

Lin

Senanayake

Cheng

et al. 2003

IEEE Trans. Electron Devices

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GaAs-based metal-oxide-semiconductor field-effect transistors (MOSFETs) are promising devices for high-speed and high-power applications. One important factor influencing the performance of a GaAs MOSFET is the characteristics of ohmic contacts at the drain and source terminals. In this paper, AuGe-Ni-Au metal contacts fabricated on a thin (930 Å) and lightly doped (4 10 17 cm 3) n-type GaAs MOSFET channel layer were studied. The effects of controllable processing factors such as the AuGe thickness, the Ni/AuGe thickness ratio, alloy temperature, and alloy time to the characteristics of the ohmic contacts were analyzed. Contact qualities including specific contact resistance, contact uniformity, and surface morphology were optimized by controlling these processing factors. Using the optimized process conditions, a specific contact resistance of 5.6 10 6 cm 2 was achieved. The deviation of contact resistance and surface roughness were improved to 1.5% and 84 Å, respectively. Using the improved ohmic contacts, high-performance GaAs MOSFETs (2 m 100 m) with a large drain current density (350 mA/mm) and a high transconductance (90 mS/mm) were fabricated.

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Low-temperature sintered AuGe/GaAs ohmic contact

Cited by 31 publications

References 10 publications

Very Stable Ge/Au/Cr/Au Ohmic Contacts to GaAs

Very Stable Ge/Au/Cr/Au Ohmic Contacts to GaAs

Development of refractory ohmic contact materials for gallium arsenide compound semiconductors

Optimization of AuGe-Ni_Au ohmic contacts for GaAs MOSFETs

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