Ohmic contacts to pseudomorphic HEMTs with low contact resistance due to enhanced Ge penetration through AlGaAs layers

Saravanan, G. Sai; Bhat, K. Mahadeva; Muraleedharan, K.; Vyas, H. P.; Muralidharan, R.; Pathak, A. P.

doi:10.1088/0268-1242/23/2/025019

Cited by 13 publications

(16 citation statements)

References 17 publications

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“…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%

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: Introductionmentioning

confidence: 99%

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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“…In order to gain Ohmic contacts, we used an Ni/AuGe/Ni/Au layer system, 13,14 which is common for contacting 2-dimensional electron gases based on GaAs/AlGaAs layer systems. 15,16 During the contact annealing, Ge diffuses into the semiconductor and occupies Ga vacancies leading to an effective n-type doping. 14 Regarding GaAs/AlGaAs core/shell nanowires, one has to be cautious, since NiAs(Ge,Ga) and Au(Ga,As) phases might extend into the nanowire during the annealing process and short-circuit two closely spaced contacts.…”

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confidence: 99%

Preparation of Ohmic contacts to GaAs/AlGaAs-core/shell-nanowires

Wirths

Mikulics

Heintzmann

et al. 2012

Applied Physics Letters

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Ohmic contacts to GaAs/AlGaAs core/shell nanowires are prepared by using a Ni/AuGe/Ni/Au layer system. In contrast to Ohmic contacts to planar GaAs/AlGaAs layer systems here, relatively low alloying temperatures are used in cylindrical geometry. Lowest resistances are found for annealing temperatures of 320 °C and 340 °C. For annealing temperatures exceeding 360 °C, the nanowires degraded completely. Nanowires annealed under optimized conditions preserved their Ohmic characteristics even down to temperatures of 4 K.

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“…In this work, Au-Ge/Ni/Au metal stack was used for ohmic metallisation of HEMT epilayers [11][12][13][14][15] . The rapid thermal annealing (RTA) promotes the intermixing of elements across the metal and semiconductor optimally so that low-contact resistance phases are formed at the interface.…”

Section: Ohmic Metallisation Of Phemt and Mhemt Device Structuresmentioning

confidence: 99%

“…The Ohmic contact provides a low resistance path for current flow, both in and out of the channel. Low contact resistance, a smooth surface morphology with minimum roughness and high thermal stability are essential requirements.In this work, Au-Ge/Ni/Au metal stack was used for ohmic metallisation of HEMT epilayers [11][12][13][14][15] . The rapid thermal annealing (RTA) promotes the intermixing of elements across the metal and semiconductor optimally so that low-contact resistance phases are formed at the interface.…”

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confidence: 99%

Microstructural and Compositional Characterisation of Electronic Materials

et al. 2016

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Microstructural and compositional characterisation of electronic materials in support of the development of GaAs, GaN and GaSb based multilayer device structures is described. Electron microscopy techniques employing nanometer and sub-nanometer scale imaging capability of structure and chemistry have been widely used to characterise various aspects of electronic and optoelectronic device structures such as InGaAs quantum dots, InGaAs pseudomorphic (pHEMT) and metamorphic (mHEMT) layers and the ohmic metallisation of GaAs and GaN high electron mobility transistors, nichrome thin film resistors, GaN heteroepitaxy on sapphire and silicon substrates, as well as InAs and GaN nanowires. They also established convergent beam electron diffraction techniques for determination of lattice distortions in III-V compound semiconductors, EBSD for crystalline misorientation studies of GaN epilayers and high-angle annular dark field techniques coupled with digital image analysis for the mapping of composition and strain in the nanometric layered structures. Also, in-situ SEM experiments were performed on ohmic metallisation of pHEMT device structures. The established electron microscopy expertise for electronic materials with demonstrated examples is presented. Keywords:Electronic materials, semiconductor electronic device, nanowires, infrared device structure REVIEW ARTICLE DEf. SCI. J., VOl. 66, NO. 4, July 2016 342 techniques for quantitative lattice distortion studies in III-V thin films & polarity of GaN based films 5,6 (e) quantitative strain/compositional studies of epitaxial thin films by the digital analysis of HRTEM images 7(f) quantitative analysis of heterointerfaces by atomic-column ratio mapping (g) in-situ SEM studies, and (h) compositional analysis by EDS and EELS techniques.An overview of GaAs, GaSb and GaN multilayer semiconductor device structures and the application of advanced electron microscopy techniques to study various issues in these materials development programs are presented. GaAs HEMt dEVIcE StructurESHEMT is a field effect transistor in which the channel is a quantum well (QW) realised by embedding a narrow bandgap semiconductor (such as InGaAs) between two wide bandgap semiconductors (e.g., GaAs and AlGaAs) and the carriers (two-dimension electron gas, 2DEG) in channel are populated by modulation doping.GaAs devices are made as pHEMTs (pseudomorphic HEMTs) and mHEMTs (metamorphic HEMTs). The schematics of these devices are shown as Fig. 1. It is to note that the increase of indium content in the In x Ga 1-x As channel enhances the saturation velocity and mobility of carriers, hence for given HEMT device features (for example, gate length), mHEMT has highest f T (the gain of the device is measured as a function of frequency, it decreases with frequency and reaches to unity at f T ), which is desirable for the device applications.grading by varying the indium content. In this case, misfit dislocations can originate and propagate as threading dislocations in the overgrown epilayers, if...

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Ohmic contacts to pseudomorphic HEMTs with low contact resistance due to enhanced Ge penetration through AlGaAs layers

Cited by 13 publications

References 17 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

Preparation of Ohmic contacts to GaAs/AlGaAs-core/shell-nanowires

Microstructural and Compositional Characterisation of Electronic Materials

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Ohmic contacts to pseudomorphic HEMTs with low contact resistance due to enhanced Ge penetration through AlGaAs layers

Cited by 13 publications

References 17 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

Preparation of Ohmic contacts to GaAs/AlGaAs-core/shell-nanowires

Microstructural and Compositional Characterisation of Electronic Materials

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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