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.

Design of a 300 GHz externally Injection-Lockable Push-Push Oscillator for Beam Steering Applications

Abstract: A design for a 300 GHz reflection type push-push oscillator including an input for an external injection locking signal is proposed. The oscillator is based on substrate transferred InP double heterojunction bipolar transistors. The intrinsic performance of the circuit is evaluated in Harmonic-Balance (HB) simulations. Furthermore, the circuit behavior under the influence of an injected signal is investigated in transient simulations and the key parameters for the locking range are derived. Additionally, a comparison of one-sided and differential injection of the locking signal is made and it is shown that the one-sided injection of the locking signal is a viable approach for the here proposed oscillator.

Numerical investigation of the effect of doping profiles on the high frequency performance of InP/InGaAs super scaled HBTs

Abstract: Our simulations show that the emitter and collector doping profile engineering is very important for the transistor optimization, in particular, adjusting the low doped emitter section to the depletion length resulted in the decrease of the emitter series resistance and increased f/sub t/ and f/sub max/; decreasing of the collector doping concentration and shrinking the collector thickness reduced the collector transit time. Accounting for the lateral diffusion of hot electrons in the device with submicron emitter was found to be important in the transistor optimization process. This effect determines the effective thickness of the emitter finger and the value of the push-out current.

Modeling the Noise of Transferred-Substrate InP DHBTs at Highest Frequencies

Abstract: This paper investigates noise modeling of transferred-substrate indium phosphide double heterobipolar transistors (InP DUBTs). It is shown that the shot noise of these devices exhibits a pronounced correlation which allows for a reliable extrapolation of the noise performance based on standard noise measurement at lower frequencies, or even on the knowledge of small-signal model parameters alone.

An InGaAs/InP HBT differential transimpedance amplifier with 47 GHz bandwidth

Abstract: In this paper, we describe an InGaAs/InP heterostructure bipolar transistor differential transimpedance amplifier with high bandwidth of 47 GHz and high gain of 56 dB-ohms.

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.