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Author

Nils Weimann

Other affiliations: Alcatel-Lucent, Agere Systems, Nokia  ...read more
Bio: Nils Weimann is an academic researcher from University of Duisburg-Essen. The author has contributed to research in topics: Heterojunction bipolar transistor & Bipolar junction transistor. The author has an hindex of 27, co-authored 160 publications receiving 7215 citations. Previous affiliations of Nils Weimann include Alcatel-Lucent & Agere Systems.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors evaluated both NiCr and TaN thin-film resistor material for use with InP technology, and determined the film stoichiometry using Rutherford backscattering and Auger electron spectroscopy analysis.
Abstract: In this study we evaluated both NiCr and TaN thin-film resistor material for use with our InP technology. Thermal stability, sensitivity to oxidation, temperature coefficients, and patterning techniques were compared for the two materials. The film stoichiometry was determined using Rutherford backscattering and Auger electron spectroscopy analysis. Electron-beam evaporation of NiCr (80:20) resulted in films that were rich in Cr (30%), due to a higher vapor pressure of Cr. Thus, it was preferentially evaporated from the source. The TaN, on the other hand, was stoichiometric to within a few atomic %. This was due to better composition control with sputter deposition as opposed to electron (e)-beam evaporation from an alloy source. The NiCr showed a 5% increase in Rs when exposed to O2 plasma, and was stable for anneal temperatures of up to 300 °C. Alternatively, the TaN was stable for O2 plasma exposure, but had an increase in Rs of 5% or 10% when annealed at 300 °C in N2 or air ambients, respectively. Fro...

13 citations

Proceedings ArticleDOI
05 Jun 2006
TL;DR: In this article, an InP-based photonic integrated circuit for high-speed digital-to-analog (DAC) conversion is presented, which achieves a single-tone spurious-free dynamic range (SFDR) of 32 dB with 4 control bits at 12.5 Gsample/s.
Abstract: We demonstrate an InP-based photonic integrated circuit for high-speed digital-to-analog (DAC) conversion. We obtained a single-tone spurious-free dynamic range (SFDR) of 32 dB with 4 control bits at 12.5 Gsample/s.

13 citations

Journal ArticleDOI
TL;DR: In this article, a transfer-substrate InP/GaAsSb double heterostructure bipolar transistors were used in a terahertz monolithic integrated circuit process for analog power applications at millimeter (mm-wave) and sub-mmwave frequencies.
Abstract: We report on the realization mymargin of transferred-substrate InP/GaAsSb double heterostructure bipolar transistors in a terahertz monolithic integrated circuit process. Transistors with 0.4- $\mu \text{m}$ -wide single emitters reached unilateral gain cutoff frequencies of around 530 GHz with simultaneous current gain cutoff frequencies above 350 GHz. Extrinsic collector capacitance is effectively reduced in the transfer-substrate process. In combination with the high collector breakdown voltage in the InP/GaAsSb heterobipolar transistor structure of 5 V, this process is amenable to analog power applications at millimeter (mm-wave) and sub-mm-wave frequencies. We demonstrate reliable extraction procedures for unilateral gain and current gain cutoff frequencies.

12 citations

Journal ArticleDOI
TL;DR: In this article, the thermal properties of submicron InP-InGaAs-InP double heterojunction bipolar transistors (DHBTs) with emitter dimensions of A = 0.25 /spl times/ 4 /spl mu/m/sup 2.
Abstract: We studied the thermal properties of submicron InP-InGaAs-InP double heterojunction bipolar transistors (DHBTs) with emitter dimensions of A = 0.25 /spl times/ 4 /spl mu/m/sup 2/. From the temperature dependence of V/sub bc/, we measured a thermal resistance of R/sub th/ = 3.3 /spl deg/C/mW for DHBTs with ion-implanted n+-InP subcollector at room temperature, compared to a high R/sub th/ = 7.5 /spl deg/C/mW from DHBTs with conventional grown InGaAs subcollector. Two-dimensional device simulations confirm the measured results.

12 citations

Proceedings ArticleDOI
11 Dec 2014
TL;DR: In this paper, a heterogeneous integration approach of bipolar technologies, using both BiCMOS and InP DHBT processes, is presented, which heavily relies on low-loss interconnects and accurate device modelling.
Abstract: Recent advances in MMIC technology have opened the possibilities for circuit operation in the THz range. There are numerous examples of BiCMOS and III-V compound device technologies with demonstrated performance beyond 600 GHz. Characterization of such MMIC are predominantly performed on-wafer in a planar environment. However, on-wafer characterization facilities do not fully keep pace with MMIC development in terms of frequency and power. The paper discusses issues involved in on-wafer calibration at mm-wave frequencies, which is the basis for accurate measurements and characterization of active and passive device. Subsequently, the paper discusses mm-wave interconnect characterization. Low-loss interconnects are important for mm-wave MMIC, especially in case of heterogeneous integration. Finally, a novel heterogeneous integration approach of bipolar technologies, using both BiCMOS and InP DHBT processes is presented. This approach heavily relies on low-loss interconnects and accurate device modelling. It will be shown that accurate large-signal models can be efficiently extracted from well-calibrated on-wafer multi-bias small-signal measurements, but verification is difficult due to calibration difficulties at mm-wave frequencies.

11 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors present a comprehensive, up-to-date compilation of band parameters for the technologically important III-V zinc blende and wurtzite compound semiconductors.
Abstract: We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

6,349 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the role of spontaneous and piezoelectric polarization on the carrier confinement at GaN/AlGaN and AlGaN/GaN interfaces.
Abstract: Carrier concentration profiles of two-dimensional electron gases are investigated in wurtzite, Ga-face AlxGa1−xN/GaN/AlxGa1−xN and N-face GaN/AlxGa1−xN/GaN heterostructures used for the fabrication of field effect transistors. Analysis of the measured electron distributions in heterostructures with AlGaN barrier layers of different Al concentrations (0.15

2,581 citations

Journal ArticleDOI
07 Nov 2002
TL;DR: This paper attempts to present the status of the technology and the market with a view of highlighting both the progress and the remaining problems of the AlGaN/GaN high-electron mobility transistor.
Abstract: Wide bandgap semiconductors are extremely attractive for the gamut of power electronics applications from power conditioning to microwave transmitters for communications and radar. Of the various materials and device technologies, the AlGaN/GaN high-electron mobility transistor seems the most promising. This paper attempts to present the status of the technology and the market with a view of highlighting both the progress and the remaining problems.

1,849 citations

Journal ArticleDOI
TL;DR: This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskiteOxides, metal nitrides, silicides, germanides, and 2D materials such as graphene.
Abstract: Materials research plays a vital role in transforming breakthrough scientific ideas into next-generation technology. Similar to the way silicon revolutionized the microelectronics industry, the proper materials can greatly impact the field of plasmonics and metamaterials. Currently, research in plasmonics and metamaterials lacks good material building blocks in order to realize useful devices. Such devices suffer from many drawbacks arising from the undesirable properties of their material building blocks, especially metals. There are many materials, other than conventional metallic components such as gold and silver, that exhibit metallic properties and provide advantages in device performance, design flexibility, fabrication, integration, and tunability. This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2D materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions.

1,836 citations

Journal ArticleDOI
TL;DR: The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed in this article, along with the influence of process-induced or grown-in defects and impurities on the device physics.
Abstract: The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

1,693 citations