Nils Weimann

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.

Modeling of InP HBTs in transferred-substrate technology for millimeter-wave applications

Abstract: In this paper, the modeling of InP heterojunction bipolar transistors (HBTs) in transferred substrate (TS) technology is investigated. At first, a direct parameter extraction methodology dedicated to III-V based HBTs is employed to determine the small-signal equivalent circuit parameters from measured S-parameters. It is shown that the model prediction of measured S-parameters can be improved in the millimeter-wave frequency range by augmenting the small-signal model with a description of AC current crowding. The extracted elements of the small-signal model structure are employed as a starting point for the extraction of a large-signal model. The developed large-signal model for the TS-HBTs accurately predicts the DC over temperature and small-signal performance over bias as well as the large-signal performance at millimeter-wave frequencies (77 GHz).

High Gain-Bandwidth InP waveguide Phototransistor

Abstract: We present a high speed phototransistor with integrated waveguide based on our InP double hetrojunction bipolar transistor (DHBT) process technology. We measured an optical-gain cutoff frequency F,* of 447 GHz with an internal optical gain of over gePt=30 at a base current of It.=650 pA using devices with emitter dimensions of A=0.7 x 4 pm2.

A 0.5 THz Signal Source with -11 dBm Peak Output Power Based on InP DHBT

Abstract: This paper presents a 0.5 THz oscillator, realized using a transferred-substrate (TS) 0.3 µm InP DHBT process. It delivers -11 dBm peak output power. The DC consumption is only 15 mW from a 1.6 volts power supply, which corresponds to 0.5 % peak DC-to-RF efficiency. The oscillator exhibits the highest efficiency of a millimeter-wave frequency source beyond 400 GHz reported to date. The core area of the circuit is only 0.6 x 0.6 mm2,

EM simulation assisted parameter extraction for the modeling of transferred-substrate InP HBTs

Abstract: In this paper an electromagnetic (EM) simulation assisted parameters extraction procedure is demonstrated for accurate modeling of down-scaled transferred-substrate InP HBTs. The external parasitic network associated with via transitions and device electrodes is carefully extracted from calibrated 3D EM simulations up to 325 GHz. Following an on-wafer multi-line Through-Reflect-Line (TRL) calibration procedure, the external parasitic network is de-embedded from the transistor measurements and the active device parameters are extracted in a reliable way. The small-signal model structure augmented with the distributed parasitic network is verified against measured S-parameters up to 110 GHz.

A 270 GHz push-push oscillator in InP-DHBT-on-BiCMOS technology

Abstract: A 270-GHz reflection-type push-push oscillator is presented, realized using 0.8μm emitter InP-DHBTs. The InP DHBT-on-BiCMOS offers both InP HBT and BiCMOS technologies but in this case only the InP part is used. The transistors exhibit a maximum oscillation frequency fmax of 300 GHz. The oscillator delivers -9.5 dBm output power. DC consumption is only 31 mW from a 1.8 volts power supply, which corresponds to 0.4 % overall DC-to-RF efficiency.

Band parameters for III–V compound semiconductors and their alloys

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.

Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N- and Ga-face AlGaN/GaN heterostructures

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

AlGaN/GaN HEMTs-an overview of device operation and applications

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.

Alternative Plasmonic Materials: Beyond Gold and Silver

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.

Gan : processing, defects, and devices

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.