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.

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.

Design of a 1-to-4 Subarray Element for Wireless Subharmonic Injection in the THz Band

Abstract: This paper presents an on-chip 1 to 4 subarray element for wireless subharmonic injection (WSI) in the context of antenna-in-antenna THz oscillators. The proposed antenna receives the third-order subharmonic injection signal (SIS) at 100 GHz from one side and radiates the 300 GHz fundamental oscillation signal (FOS) to the opposite side, which performs like a subharmonic transmitarray. Each element is consisted of a single SIS receiving antenna (Receiver antenna, RA) connected with a $2\times 2$ FOS array (Transmitter antenna, TA). By positioning more FOS antenna around the single SIS antenna, the element spacing at 300 GHz is shorted within one wavelength which inhibits the grating lobe. Through tuning the distance of the FOS array element, the surface wave in the thick indium phosphide (InP) substrate is also reduced to some degree. The simulation results show that the maximum radiation efficiency of the designed chip antenna structure is better than 50% in both the 100 GHz and the 300 GHz band. The conjugate impedance matching in the dual-band is achieved according to the active element requirement. Utilizing the antenna proposed in this work, a low injection loss is verified in the periodical boundary based WSI simulation.

Planar arrays of photodiodes

Abstract: An apparatus includes a light detector. The light detector includes a substrate with a planar surface and an array of photodiodes located along the planar surface. Each photodiode has a sequence of different semiconductor layers stacked vertically over the planar surface. The photodiodes are electrically connected in series.

Balanced G-band Gm-boosted frequency doublers in transferred substrate InP HBT technology

Abstract: In this paper, balanced G-band Gm-boosted frequency doublers in transferred substrate (TS) InP HBT technology are reported for the first time. The Gm-boosted frequency doublers consist of a phase compensated Marchand balun, Gm-boosted doubler stage, and an optional cascode gain stage at the output. The doubler without cascode demonstrates a maximum output power of +4.7 dBm around a narrow frequency range at 200 GHz when driven with an input power of +10 dBm. A Gm-boosted frequency doubler with cascode demonstrates an output power of +5.4 dBm at 190 GHz when driven with an input power of +11 dBm. The power consumptions of the Gm-boosted frequency doubler without and with cascode are 30.9 mW and 56.4 mW, respectively. The fundamental suppression for both doublers remains better than 17.3 dB over an input frequency range of 75–110 GHz.

Transmitarray Element Design for Subharmonic Injection-locked RTD Oscillators in THz Band

Abstract: In this paper, a transmitarray element (TE) is designed for wireless subharmonic injection-locked triple barrier (TB) resonant tunneling diode (RTD) oscillators. It adopts a receiver antenna (RA)-transmitter antenna (TA) structure. The RA is a u-slotted patch antenna, and we use a cubic silicon block at top of this patch, so as to increases the RA gain and radiation efficiency. A fat monopole structure with a slot-like counterpoise is used as the TA. In this design, the RA can receive 100 GHz subharmonic injection signal (SIS). Meanwhile, the TA will radiate the 300 GHz fundamental oscillation signal (FOS) generated by the TB RTD. Moreover, the TA structure can isolate the 300 GHz FOS coming into the RA but couple the received 100 GHz SIS to the TB RTD, which performs like a filter-antenna. In the simulation, the transmission loss in the TA structure is higher than 15 dB around 300 GHz and only about 1.5 dB around 100 GHz. The gain of RA is 6 dBi with 65% radiation efficiency at 100 GHz and the gain of TA is 14 dBi at 300 GHz when applying a 1 mm radius silicon lens at the backside of the InP substrate.

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.