An investigation of a nonspiking Ohmic contact to n-GaAs using the Si/Pd system

Wang, L. C.; Zhang, B.; Fang, F.; Marshall, E. D.; Lau, S. S.; Sands, T.; Kuech, T. F.

doi:10.1557/jmr.1988.0922

Cited by 65 publications

(11 citation statements)

References 18 publications

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“…Through the judicious choice of film thicknesses and annealing temperatures both types of solid state regrowth were accomplished in practice. Figure 6 shows the evolution of Si/Pd/GaAs system as deduced from Rutheford backscattering (RBS), X-ray diffraction (XRD) and TEM analysis [54,55].…”

Section: Gold-free Ohmic Contactsmentioning

confidence: 99%

Ohmic Contacts to GaAs: Fundamentals and Practice

Piotrowska

1993

Acta Phys. Pol. A

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Recent advances in the technology and understanding of ohmic contacts to GaAs are presented. The paper emphasizes the reactions at the metal/GaAs interface and the structural factors which govern its electrical behavior and long-term stability. Results on the optimization of conventional gold-based ohmic contacts together with recent achievements in the technology of non-alloyed.contacts are overviewed.PACS numbers: 73.40Ns Criteria for a good ohmic contactModern device concepts strongly depend on reliable and well-controlled electrical contacts through which one has to communicate with the interior of the device from the outside world. In particular, micron and submicron size Ill-V devices can be fully exploited only with adequate ohmic contacts. In addition to a wide variety of device and circuit applications, good quality ohmic contacts are required for investigating the physical and electrical properties of bulk materials and related III-V heterostructures. Consequently, much attention has been recently devoted to the development of ohmic contacts to III-V materials, and the research area include both, the fundamental behavior of metal/semiconductor contacts and the new techniques for improving the properties of ohmic contacts [1][2][3][4][5][6][7].The purpose of this paper is to bring together much of the fundamental and practical knowledge on the formation of ohmic contacts to GaAs. First, we give brief overview of the requirements for ohmic contacts in modern GaAs devices. Next, we shall comment on the actual state of understanding of the formation of potential barriers developing at metal/GaAs interfaces. While the detailed discussion of theories of metal/GaAs interface is beyond the scope of this article, basic concepts applicable to fabricate low-resistance contacts will be provided. The main part of the paper is devoted to up-todate approaches in the fabrication of ohmic contacts. We shall emphasize the reactions at the metal/semiconductor interface and the stuctural factors which govern its electrical behavior and long-term stability. Key technological issues of advanced contact technology will be given in Sec. 4.The main constraint on the choice of material for an ohmic contact is to ensure that it has the correct electrical properties. They are characterized by the (491)

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Section: Gold-free Ohmic Contactsmentioning

confidence: 99%

Ohmic Contacts to GaAs: Fundamentals and Practice

Piotrowska

1993

Acta Phys. Pol. A

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“…More recently a comparison with the SilPd/GaAs (Ref. 9) and SiiNilGaAs (Ref. 15) systems led to the suggestion that the ohmic behavior for these systems results from heavy doping of a regrown GaAs layer by the group-IV element rather than from the formation of a Ge/GaAs heterojunction.…”

Section: Solid~phase Epitaxial Growthmentioning

confidence: 99%

“…7 ,8 In this case a palladium german ide was formed, and the excess Ge penetrated through the layer toward the substrate. The formation of the ohmic contact was originallyH attributed to the formation of a low barrier heterojunction by the epitaxial growth of the excess Ge on top ofihe GaAs surface; however, a comparison with the SilPd/GaAs system has recently led 9 to the suggestion that the ohmic behavior results from heavy Ge doping of a regrown GaAs top layer which leads to a tunneling contact.…”

Section: Introductionmentioning

confidence: 99%

Study of the Co-Ge/GaAs contact system

Genut¹,

Eizenberg²

1990

Journal of Applied Physics

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The interfacial reactions between thin films of cobalt and germanium and (001)-oriented GaAs substrates in two configurations, Co/Ge/GaAs and Ge/Co/GaAs, were studied. The microstructure and phase formation, as analyzed by transmission electron microscopy, x-ray diffraction, and Auger electron spectroscopy, were correlated with the electrical properties of these contacts, as determined by current-voltage and capacitance-voltage measurements. At low temperatures, 250≤T<325 °C, the only reaction that was monitored was the formation of Co5Ge7 at the outer interface, while the GaAs substrate remained intact. The growth of Co5Ge7 was diffusion limited with an activation energy of ∼0.7 eV. At the temperature range of 325–400 °C for both metalizations epitaxial Co2GaAs was formed on top of the GaAs beneath the Co5Ge7 layer. For the Ge/Co/GaAs metalization this was accompanied (at 400 °C) by solid-phase epitaxial growth of Ge precipitates on the GaAs surface. Contacts produced in this annealing regime were rectifying with nearly ideal thermionic emission behavior. The Co2GaAs phase was unstable at higher temperatures (500–600 °C), and the reaction products were two ternary phases, with compositions of Co2GeGa and Co2GeAs. These compounds were spatially separated—the Co2GeGa layer on top of the Co2GeAs phase. Contacts produced at the high-temperature regime (>400 °C) had very low effective barriers and on an n+ GaAs substrate became ohmic.

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“…Non-spiking III-V ohmic contacts based on Ge/Pd and Si/Pd metallizations offer improvements in contact resistivity, morphology, and thermal stability as compared to conventional Au based contacts [1][2][3]. These non-spiking contacts rely on the phenomenon of solid phase regrowth (SPR) to produce abrupt metal-semiconductor interfaces, which thereby lend themselves to more straightforward characterization by microscopy or spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Ge/Pd and Si/Pd/Ge/Pd Non-Alloyed Ohmic Contacts to InP Examined by Backside Secondary Ion Mass Spectrometry

Schwarz¹,

Sands²,

Bhat³

et al. 1992

MRS Proc.

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High resolution SIMS (secondary ion mass spectrometry) depth profiles of Ge/Pd and Si/Pd/Ge/Pd non-alloyed ohmic contacts on InP are obtained by sputter-etching from the back (semiconductor) side. The samples contain an InGaAs etch stop layer, to allow chemical thinning, and InGaAsP marker layers, which allow alignment and calibration of the depth profiles. Detailed comparisons are made to corresponding contacts on GaAs, processed and analyzed under similar conditions. The importance of interfacial alloy formation, semiconductor regrowth, and dopant incorporation are highlighted.

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An investigation of a nonspiking Ohmic contact to n-GaAs using the Si/Pd system

Cited by 65 publications

References 18 publications

Ohmic Contacts to GaAs: Fundamentals and Practice

Ohmic Contacts to GaAs: Fundamentals and Practice

Study of the Co-Ge/GaAs contact system

Ge/Pd and Si/Pd/Ge/Pd Non-Alloyed Ohmic Contacts to InP Examined by Backside Secondary Ion Mass Spectrometry

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