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Malmros A.,Chalmers University of Technology | Blanck H.,United Monolithic Semiconductors GmbH | Rorsman N.,Chalmers University of Technology
Semiconductor Science and Technology | Year: 2011

Ta-based ohmic contacts to gallium nitride high electron mobility transistor (GaN HEMT) epitaxial structures were investigated. Two metallization schemes were considered: Ta/Al/Ni(Ta)/Au and Ta/Al/Ta. The latter was superior in terms of lower contact resistance (Rc) and wider process window. The metallizations were applied to two different heterostructures (GaN/Al 0.14Ga0.86N/GaN and Al0.25Ga 0.75N/GaN). The lowest measured Rc was 0.06 and 0.28 Ω mm, respectively. The main advantage of the Ta-based ohmic contacts over conventional Ti-based contacts was the low anneal temperature. The optimum temperature of annealing was found to be 550-575 °C. From optical and scanning electron microscopy, it was clear that excellent surface morphology and edge acuity were obtained at these low temperatures. This facilitates lateral scaling of the GaN HEMT. TEM images were taken of the contact cross sections onto which EDX measurements were performed. The aim was to investigate the microstructure and the contact mechanism. Storage tests at 300 °C for more than 400 h in air ambient showed no deterioration of Rc. © 2011 IOP Publishing Ltd. Source


Huber F.,University of Ulm | Madel M.,University of Ulm | Madel M.,United Monolithic Semiconductors GmbH | Reiser A.,University of Ulm | And 3 more authors.
Journal of Crystal Growth | Year: 2016

High-quality zinc oxide (ZnO) layers were grown using a new chemical vapour deposition (CVD)-based low-cost growth method. The process is characterized by total simplicity, high growth rates, and cheap, less hazardous precursors. To produce elementary zinc vapour, methane (CH4) is used to reduce a ZnO powder. By re-oxidizing the zinc with pure oxygen, highly crystalline ZnO layers were grown on gallium nitride (GaN) layers and on sapphire substrates with an aluminum nitride (AlN) nucleation layer. Using simple CH4 as precursor has the big advantage of good controllability and the avoidance of highly toxic gases like nitrogen oxides. In photoluminescence (PL) measurements the samples show a strong near-band-edge emission and a sharp line width at 5 K. The good crystal quality has been confirmed in high resolution X-ray diffraction (HRXRD) measurements. This new growth method has great potential for industrial large-scale production of high-quality single crystal ZnO layers. © 2016 Elsevier B.V. All rights reserved. Source


Patent
United Monolithic Semiconductors Gmbh | Date: 2011-05-12

For an HEMT component, in particular on the basis of GaN, it is proposed, for the purpose of reducing field spikes in the conduction channel, in a partial section of the conduction channel between gate electrode and drain electrode, to set the sheet resistance of the conduction channel such that it is higher than in adjacent regions. Various measures for subsequently increasing the sheet resistance in an area-selective manner are specified.


The invention relates to an electronic component having a circuit integrated on a semiconductor substrate, and a heat-conducting connection of the substrate by soldering using a carrier serving as a heat sink, wherein the invention proposes depositing a first, thicker Au layer (


Camiade M.,United Monolithic Semiconductors SAS | Bouw D.,United Monolithic Semiconductors SAS | Mouginot G.,United Monolithic Semiconductors SAS | Auvray F.,United Monolithic Semiconductors SAS | And 5 more authors.
European Microwave Week 2012: "Space for Microwaves", EuMW 2012, Conference Proceedings - 42nd European Microwave Conference, EuMC 2012 | Year: 2012

This paper presents recent results on highly integrated internally-matched Gallium Nitride transistors in S and C-band. The concept and the advantages of 'Quasi MMIC' devices are described, showing the high potentialities for performance improvements and cost reductions. Using Gallium Arsenide based passive MMICs for input and/or output matching, more than 50W has been obtained at S-band with more than 55% PAE from 2.9GHz to 3.5GHz and more than 45% PAE at C-band @ 6.2GHz. © 2012 EUROPEAN MICROWAVE ASSOC. Source

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