Section Semiconductor Nanostructures

Section Semiconductor Nanostructures

Mission

Crystalline elements are crucial components of innovative technologies. As these technologies become increasingly smaller, it is essential that the dimensions of the crystalline structures decrease and that the crystallites are formed on the substrates in a very controlled manner. For this reason, it is the task of the Section Semiconductor Nanostructures to investigate the growth and local control of nano- and microcrystallites and to develop new methods for their implementation.

Research activities

Low-dimensional growth concepts are beeing applied towards the use in novel technologies in this group. These comprise nanowire growth for new field-effect transistors, micro-island generation and thin-film growth from solution both for novel solar concepts as well as deposition of ultra-thin strained layers for the use in quantum computers. Not only technology development and characterization, but also concepts and realization of novel growth systems are in the focus. Within the framework of a Leibniz-funded project an MBE for the deposition of ultrapure 28Si layers is currently being developed and, in the course of a BMWi joint project, a CVD system for laser-assisted local nucleation processes is being built.

Topics

Growth of Si on glass for low-cost solar cells

In a unique process developed at IKZ, crystalline silicon is grown from tin solution on various substrates. This allows for the deposition on glass in a continuous process, which enables the production of cost-efficient and large-scale absorbers for photovoltaics. Due to the epitaxy from tin close to the thermodynamic equilibrium, the material has a high crystalline perfection and thus promising electrical properties. The use of silicon and the low energy consumption make for an ecologic and economic method.

In a cooperation with PVcomB, their know-how in silicon thin film solar cells is applied to build cells from layers grown at IKZ. Hereby not only silicon on glass, but also silicon on alternative substrates in IMEC Epifoils® and monocrystalline silicon is accessed. Additionally, IKZ`s high-tech equipment in material science as Raman Spectroscopy, in situ TEM and XRD is used for in-depth characterization and improvement of layer quality.

Christian Ehlers, Stefan Kayser, David Uebel, Roman Bansen, Toni Markurt, Thomas Teubner, Karsten Hinrichs, Owen Ernst, Torsten Boeck
In situ removal of a native oxide layer from an amorphous silicon surface with a UV laser for subsequent layer growth
CrystEngComm (2018)
DOI: 10.1039/C8CE01170B

Contact

David Uebel

Ph. +49 30 6392 3238

Email

Locally defined and laser-assisted nucleation

Top-down methods such as mask techniques or lithography are well established processes that suffer from limited throughput scalability and thus high cost. For this reason, it is the aim of the group locally defined nucleation to theoretically describe and develop alternative bottom-up possibilities for local structure formation. In this context, dewetting processes for nanoparticle synthesis and laser-induced nucleation play an major role.

The goal of the research is the formation of compound semiconductor micro-islands, for example Cu(In,Ga)Se2 for solar cells, which allows for saving up to 99% of the precursor material compared to conventional thin film methods. For this purpose, new nucleation models are being developed and implemented in practice: for instance, local modification of surface morphologies, as well as laser-assisted thermolysis of metal precursors.

This work is part of a joint project with BesTec GmbH, BAM and Uni-DUE and funded by the BMWi.

Owen Ernst, Felix Lange, Thomas Teubner, Torsten Boeck
Analysis of catalyst surface wetting: the early stage of epitaxial germanium nanowire growth
Beilstein Journal of Nanotechnology 11 (2020) 1371–1380
DOI: 10.3762/bjnano.11.121

Franziska Ringleb, Stefan Andree, Berit Heidmann, Jörn Bonse, Katharina Eylers, Owen Ernst, Torsten Boeck, Martina Schmid, Jörg Krüger
Femtosecond laser-assisted fabrication of chalcopyrite micro-concentrator photovoltaics
Beilstein Journal of Nanotechnology 9 (2018) 3025-3038
DOI: 10.3762/bjnano.9.281

Torsten Boeck, Roman Bansen, Franziska Ringleb
Growth of crystalline semiconductor films and micro structures for photovoltaic applications
Crystal Research and Technology 52 (2017) 1600239
DOI: 10.1002/crat.201600239

Contact

Owen Ernst

Ph. +49 30 6392 2847

Email

Growth of Si/Ge Nanostructures

Due to their small diameter and potentially high crystalline quality, nanowires are very interesting for future applications such as thermoelectrics, sensors and field-effect transistors. Using molecular beam epitaxy (MBE) the selective growth behaviour of SixGe1-x nanowires is investigated in ultra-high vacuum. For this purpose, we focus on various aspects of epitaxy, such as thermodynamic phase formation, nucleation and surface diffusion processes.

With the "vapor-liquid-solid" (VLS) method, nanowires are grown using a gold nanocatalyst. For this purpose, gold droplets are formed on various crystalline substrates, on which nanowire growth is subsequently performed by depositing Si/Ge material. The focus is set on incorporation of Ge in SixGe1-x out-of-plane nanowires and local growth of Ge nanowires along the substrate surface.

Felix Lange, Owen Ernst, Thomas Teubner, Carsten Richter, Martin Schmidbauer, Oliver Skibitzki, Thomas Schroeder, Peer Schmidt, Torsten Boeck
In-plane growth of germanium nanowires on nanostructured Si(001)/SiO2 substrates
Nano Futures 4 (2020) 035006
DOI: 10.1088/2399-1984/ab82a0

Contact

Felix Lange

Ph. +49 30 6392 2852

Email

High Definition Crystalline Silicon-Germanium Structures for Quantum Circuits

Quantum circuits based on isotope pure 28Si layers have the perspective to become the most scalable approach towards quantum computation technology. To realize qubits, the quantum confinement is performed in strained Si within Si-Ge heterostructures. The project combines IKZ`s expertise in molecular beam epitaxy (MBE) technique and handling of isotope pure 28Si to fabricate a highly pure, low-defect and atomically flat strained 28Si layer.

To achieve high-quality strained Si layer, there are two strategies proposed: one strategy is to control the Si composition in top and bottom layers of SiGe/Si/SiGe heterostructure; in the other strategy, a SiGe superlattice structure is designed to avoid alloy clustering and meanwhile to give the strain state. Both approaches pursue to control the interface of the strained Si since the single-atom terrace influences the spin coherence through its effect on valley splitting.

This work is funded by Leibniz collaborative research project and shared with partner institutes IHP (Frankfurt/Oder) and Rhein-Westfählische Technische Hochschule (RWTH Aachen).

Contact

Yujia Liu

Ph. +49 30 6392 3055

Email