Current Projects and Theses

The topics listed below are currently offered as project or final theses.

However, due to constant developments in current research projects, this list is not complete and gives examples of possible tasks.

If you are interested in a specific topic, please inform yourself about currently offered tasks

Contact person: Dr.-Ing. Werner Prost, Prof. Dr. Nils Weimann

Currently Available Tasks

(M.Sc.) Physical Analysis and Design of a highly-linear and low-noise InP DHBT in a TCAD Simulator

Background:

With the upcoming demand for higher data-rates (5G) the need for higher frequencies up to 130 GHz arises, which poses great challenges for the measurement instrument market. Among the III-V semiconductor technologies, InP Heterojunction Bipolar Transistor technology is known to be a very promising candidate to realize high-bandwidth, and large voltage swing mm-wave (mmW) analog circuits. Applications in measurement instruments require linear and low-noise integrated circuits. Exact physical design trade-offs to build linear and low-noise InP DHBT structures have not been treated by the scientific world so far, and are thus within the scope of this master´s thesis.

Task:

Goal of this thesis work is the analysis by simulation of the physical trade-offs together with the design of a doubleheterojunction bipolar transistor (DHBT) in InP technology, which exhibits high linearity and lownoise performance at the same time. By means of the TCAD device simulators Taurus Medici (2D) / Sentaurus (3D) the optimal material grading, doping profiles and layout geometries of a triple-mesa DHBT shall be elaborated w.r.t. the measurable quantities harmonic distortion (HD) / 3rd order intercept point (IP3) and noise figure (NF) to find the optimum device structure for realizing a highly linear but low-noise InP DHBT. The resulting structure will be realized by BHE’s epitaxy group and feed into BHE’s InP HBT THz circuit process.

This Master thesis is offered in cooperation with Rohde & Schwarz, Munich.

Task Master thesis

Supervisor: Prof. Dr. Nils Weimann

(M.Sc. Project/M.Sc.) 3D Electromagnetic Design of RTD Antenna Arrays

Background:

In the terahertz (THz) range between 300 GHz and 4 THz, many novel applications are currently developing: contactless material recognition and characterization, ultra-fast wireless data transmission of several Tbit/s, detection of hidden objects in robotics and security applications. For these applications compact signal sources and detectors are required, which provide high output power efficiently, detect sensitively and with low noise, and can be manufactured compactly, robustly and cost-effectively.

In the SFB/TRR196 MARIE we investigate the resonant tunnel diode (RTD), a device based on the quantum mechanical tunneling effect, which can be used to generate signals up to 2 THz. By improving the semiconductor vertical structure, the device manufacturing processes and the interconnection in arrays we try to improve the performance of these THz components.

Task:

The output power of electronic THz components can be increased by parallel connection. Since passive waveguide networks are very lossy in the THz range, we investigate the free beam combination of RTD in phase-locked arrays. A challenge is the correct integration of the RTD into a suitable antenna structure. Here, active component and passive antenna structure have to be sensibly matched to each other in order to oscillate at the desired frequencies with high output power. Using industry standard 3D-EM simulation software (Empire XPU and CST Microwave Studio), a reasonable concept for the integration of the RTD in an oscillator configuration is to be developed in a simulation. Subsequently, a circuit layout will be created and components will be manufactured in the clean room of the ZHO and measured at THz frequencies.

Supervisor: M.Sc. Robin Kreß

(B.Sc. Project) Optimization of Electrical Contacts in Resonant Tunnel Diodes

Background:

In the terahertz (THz) range between 300 GHz and 4 THz, many novel applications are currently developing: contactless material recognition and characterization, ultra-fast wireless data transmission of several Tbit/s, detection of hidden objects in robotics and security applications. For these applications compact signal sources and detectors are required, which provide high output power efficiently, detect sensitively and with low noise, and can be manufactured compactly, robustly and cost-effectively.

In the SFB/TRR196 MARIE we investigate the resonant tunnel diode (RTD), a device based on the quantum mechanical tunneling effect, which can be used to generate signals up to 2 THz. By improving the semiconductor vertical structure, the device manufacturing processes and the interconnection in arrays we try to improve the performance of these THz components.

Task:

For operation at highest frequencies, one of the limiting factors is the series resistance of the RTD by determining the passive RC time constant and reducing the internal gain of the RTD. In this thesis the electrical contact of the RTD structure shall be experimentally investigated and improved. To analyze the contact, test structures as well as single components are manufactured and measured. The characterization of the device is done by network analysis with our state-of-the-art measurement equipment. Using a simple small-signal equivalent circuit diagram, the RTD will be modeled and key parameters such as series resistance, conductance and total capacitance will be extracted.

Supervisor: M.Sc. Enes Mutlu

(B.Sc./M.Sc.) Process Development for Galvanically Manufactured RTD Antenna Structures

In the terahertz (THz) range between 300 GHz and 4 THz, many novel applications are currently developing: contactless material recognition and characterization, ultra-fast wireless data transmission of several Tbit/s, detection of hidden objects in robotics and security applications. For these applications compact signal sources and detectors are required, which provide high output power efficiently, detect sensitively and with low noise, and can be manufactured compactly, robustly and cost-effectively.

Due to the small wavelength, the structures to be manufactured for this purpose must be particularly small and detailed. For the production of such metallic structures made of gold, the deposition by electroplating is a suitable method. In this way, particularly high layer thicknesses can be reliably produced with a good aspect ratio.

Task:

An existing process for the stubbornly cut deposition of gold on InP chips must be further developed. The aim is to integrate it into the existing RTD oscillator process so that current and future antenna structures can be manufactured. A concept has to be developed here so that the previously existing RTD is not damaged during the plating process. The optimization of the connections of the galvanized antennas to the RTD is a further milestone.

Supervisor: M.Sc. Robin Kreß

(M.Sc.) TCAD Simulation of RTD Structures

Background:

In the terahertz (THz) range between 300 GHz and 4 THz, many novel applications are currently developing: contactless material recognition and characterization, ultra-fast wireless data transmission of several Tbit/s, detection of hidden objects in robotics and security applications. For these applications compact signal sources and detectors are required, which provide high output power efficiently, detect sensitively and with low noise, and can be manufactured compactly, robustly and cost-effectively.

In the SFB/TRR196 MARIE we investigate the resonant tunnel diode (RTD), a device based on the quantum mechanical tunneling effect, which can be used to generate signals up to 2 THz. By improving the semiconductor vertical structure, the device manufacturing processes and the interconnection in arrays we try to improve the performance of these THz components.

Task:

The essential properties of RTD are determined by its epitaxially grown layer structure. The core of an RTD layer contains several quantum barriers (e.g. AlAs) and quantum wells (e.g. InGaAs), between which resonant electron states exist. The resulting resonant tunnel current is strongly nonlinear and is used to generate THz oscillations. The electronic behavior of the RTD structure is calculated and optimized by specialized software packages, so-called TCAD simulators. We use industry standard software from Synopsys. The goal of this work is to optimize the performance of the RTD with respect to higher oscillation frequency and oscillation power by simulations based on existing layer packages. A subsequent experimental fabrication of devices in the clean room of the ZHO and characterization at THz frequencies is planned.

Supervisor: M.Sc. Enes Mutlu

(M.Sc./B.Sc.) Selective Contacting and Characterization of (In)GaN Nanowire LEDs

Gallium Nitride (GaN) is the basic material for the production of light emitting diodes (LED). With the ternary indium-gallium-nitride (InxGa1-xN) compound, the color of the light of the LED can be adjusted over the entire visible spectral range. In the BHE GaN based nanowire LEDs (ND-LEDs) are manufactured. Due to the nanowire geometry the ND-LED potentially has several advantages over conventional layered LEDs. The luminous active area is increased compared to the surface of the substrate and the electro-optical properties of the ND-LEDs enable them to be used in the high-frequency range.

High data rates make ND-LEDs attractive for communication technology. In order to optimize the LEDs in this respect, the electro-optical characterization of single wires and whole fields of several 1000 ND-LEDs is necessary. Due to the complex structure of the ND-LED the contacting is a technological challenge. Optimization of current injection into the LEDs by selective electrical insulation and conformal covering with indium tin oxide (ITO) are only examples of such challenges for contacting of whole fields. Furthermore, an understanding of the charge carrier transport through the ND-LEDs is important for their optimization. For this purpose single ND-LEDs are preferably contacted and electrically measured. By explaining the current-voltage characteristics with corresponding mechanisms for the charge carrier transport, a model of the current transport through the ND-LEDs can be developed. Based on the model, limiting factors can be extracted and optimized.

If you are interested in this topic, please contact us for further information.

Supervisor: M.Sc. Patrick Häuser

(M.Sc. Project, M.Sc.) Design of a Differential Low-Noise Amplifier in the Range of 150-250 GHz Based on InP DHBTs

Background:

Within the framework of the SFB/TRR 196 MARIE, a network of seven universities and research institutes is conducting research on mobile material characterization and localization based on THz- and sub-THz radiation in the range of 250 GHz to 4 THz. A major problem is the high ambient loss of THz radiation in the air. These make powerful compact sources with a directed beam attractive. One approach for directed beams are so called "phased arrays", where the phases of the individual oscillators are controlled in an oscillator array, thus forming a directed beam by interference of all output signals. An efficient method for phase control of oscillators is "injection-locking". In this phenomenon the phase and output frequency of an oscillator can be controlled by injecting a weak signal close to the original oscillation frequency. The signal quality of the locking signal is crucial for the quality of the output signal of the locked oscillator. To make the injection-locking unilateral and to generate a sufficiently strong locking signal, the use of low-noise amplifier circuits is recommended.

Task Definition:

For this purpose a differential amplifier based on the current InP DHBT process of the Ferdinand Braun Institute will be developed. First, the schematic layout will be designed in a circuit simulation software (Advanced Design Systems) using a design kit provided by FBH. The topology of the amplifier will be optimized with respect to the signal-to-noise ratio and a high isolation of input and output. Subsequently, a physical layout will be developed and simulated with state-of-the-art 3D-EM software (CST Microwave Studio, Empire XPS). An HPC (High Performance Computing) server cluster is available for the simulations. Furthermore, the coupling of the amplifier signal into the oscillator will be optimized. The designed circuit is then manufactured at FBH and integrated into the overall circuit.

Activities/Profile:

Literature research on RF circuit design, working with industry standard circuit design software, 3D-EM simulations (FEM, FDTD, Momentum)
Experience with circuit design software is desirable but not a prerequisite.
Support is available in German and English.

If you are interested in the topic, please contact us for further information.

Supervisor: M.Sc. Alexander Poßberg