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PD Dr. techn. Gregor Koblmüller

Phone
+49 89 289-12779
Room
E-Mail
gregor.koblmueller@tum.de
Links
Page in TUMonline
Groups
Semiconductor Nanostructures and Quantum Systems
TUM Department of Physics
Job Title
PD at the Physics Department

Courses and Dates

Offered Bachelor’s or Master’s Theses Topics

3D-Structured III-V Nanowires for Ultrahigh-Efficiency Solar Cells

At the Walter Schottky Institute (WSI-TUM) we recently launched a research project directed to the exploration of new types of high-efficiency solar cell systems based on 3D-structured III-V semiconductor nanowires.

Conventional single-cell photovoltaic devices are known to have performance limits due to large thermal and spectral losses, light trapping issues and charge carrier losses. To overcome these problems 3D-structured nanowire (NW) solar cells have emerged as promising systems with improved light trapping and absorption properties beyond the ray-optic limit, as well as better carrier collection efficiencies.

The goal of this M.Sc. project is to exploit the advantages of 3D-structured III-V semiconductor NWs and work towards a novel hot carrier solar cell (HCSC), which allows to selectively cool charge carriers and reduce thermal losses. Hereby, you will be closely working together with two PhD students to first design proper bottom-up III-V NW heterostructures from the group-III-V family of semiconductors. Exploiting the full geometrical and energy-selective parameter space, the design will be directly guided by in-depth simulations for enhanced photoabsorption and effective carrier thermalization properties. NW heterostructures on lithographically patterned substrates should then be realized by top-down/bottom-up nanofabrication processes and further characterized by various optical spectroscopy methods (photoluminescence, FTIR, and UV-Vis-NIR absorption spectroscopy). Finally, the goal is to identify correlations between array-geometry, NW dimensions, and electronic properties of the selected heterostructure material (band gap and strain) and the corresponding optical and charge carrier responses.

You will gain & learn:

  • Knowledge in electromagnetic (FDTD) and electronic band structure simulations (nextnano)
  • Advanced lithography / clean-room processes for state-of-the art 3D structured NWs
  • Diverse optical spectroscopy (micro-Photoluminescence, FTIR, UV-Vis-NIR absorption)
  • Correlated microscopy methods (SEM, He-Ion Microscopy)

Experience in the area of clean room fabrication, optical spectroscopy or nanoanalytics, as well as experience in simulations is a benefit, but secondary to motivation and commitment. Applications should be sent to Gregor.Koblmueller@wsi.tum.de and Jonathan.Finley@wsi.tum.de. Please include your CV, and a transcript of records (Bachelor & Master).

May 2019

suitable as
  • Master’s Thesis Condensed Matter Physics
  • Master’s Thesis Applied and Engineering Physics
Supervisor: Gregor Koblmüller
Advanced Nano-Thermoelectrics based on III-V Semiconductor Nanowires

At the Walter Schottky Institute (WSI-TUM) we currently conduct an extensive research program on the realization of high carrier mobility III-V semiconductor nanowires and their application in next generation ultrascaled nanoelectronics and thermoelectric energy conversion.

An important step towards high performance nano-thermoelectric devices is the development of suitable high carrier mobility materials which simultaneously allow high electrical conductivity and large Seebeck coefficient, while minimizing thermal conductivity. In this regard, 1D-semiconductor nanowires are very promising nano-thermoelectric systems, since they exhibit reduced density of states (DOS) and complex core-multishell structure design enabling to meet all these relevant criteria.

The goal of this M.Sc. project is to explore novel modulation doped InAs/AlSb core-multishell nanowire heterostructures and investigate their potentials in nano-thermoelectrics by a combination of semi-classical and quantum transport experiments as well as characterization of thermal transport. Interacting closely with two PhD students you will be designing the proper InAs/AlSb nanowire materials and further transform these into 2- or 4-terminal nanowire-field effect transistor (NWFET) devices together with resistively coupled heaters using advanced nanolitho­graphy methods in state-of-the art cleanroom facilities. These nano-thermoelectric devices should be then characterized with respect to their internal structure and 1D-DOS, contact behavior, carrier density and channel length in order to identify different regimes of transport and thermopower using temperature-dependent electrical transport spectroscopy. In addition, thermal transport on these systems will also be characterized using a novel non-destructive optical technique (Raman spectroscopy).

You will gain & learn:

  • Knowledge in design of low-dimensional III-V semiconductors with high carrier mobility
  • Fabrication of nanoelectronic & nano-thermoelectric devices using nano-lithography
  • Experience in low-noise, low-temperature electrical transport characterization
  • Experience in optical spectroscopy, specifically Raman spectroscopy
  • Diverse microscopy methods (AFM, SEM, He-Ion Microscopy)

     

      Experience in the area of clean room fabrication, nanoanalytics or (nano)electronics, as well as experience using Matlab is a benefit, but secondary to motivation and commitment. Applications should be sent to Gregor.Koblmueller@wsi.tum.de and Jonathan.Finley@wsi.tum.de. Please include your CV, and a transcript of records (Bachelor & Master).                  May2019

M

M

suitable as
  • Master’s Thesis Condensed Matter Physics
  • Master’s Thesis Applied and Engineering Physics
Supervisor: Gregor Koblmüller
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