Applications are invited for a 3-year PhD position within the field of epitaxial growth of novel quantum dot (QD) gain material employing the selective area growth method assisted by block copolymer lithography.
The project is interdisciplinary and will bring together several topics in the fields of semiconductor QD epitaxial growth, block copolymer lithography, optical characterization, theoretical simulations of electronic properties of QDs, and photonic device fabrication.
The project will be carried out at the Department of Photonics Engineering in collaboration with the Department of Micro and Nanotechnology at the Technical University of Denmark (DTU) in collaboration with the Technical University of Berlin in Germany and the University of Rome Tor Vergata in Italy. An external research stay at the Technical University of Berlin will be possible.
The PhD-project is funded through the Villum foundation’s Young Investigator Programme awarded to Dr. Semenova.
The progress in a number of areas like telecommunication, optical coherence tomography including medical applications, sensing, computer and network clock-distribution, THz generation, metrology, etc. relies on the development of semiconductor optical devices with low threshold current densities, low temperature dependence, low noise, and for mode-locked lasers short pulse operation. The key for archiving these laser performances is a superior low dimensional gain medium. After several decades of research huge progress was demonstrated for laser devices based on self-assembled QDs in the gallium arsenide (GaAs) material system .
Unfortunately, QD material on GaAs has a limited spectral coverage which in practice is 1-1.3 µm. For longer wavelength emission and for photonic integrated circuits indium phosphide (InP) is normally used as base material. However, the self-assembled QDs on this substrate have so far not been able to reproduce the superior properties of their short wavelength counterparts.
As an alternative to the self-assembled approach, which is ultimately limited by the material properties and growth dynamics, is selective area growth (SAG), where the growth of QDs is carried out in the nano-openings of a glass mask. This approach allows for the formation of arrays of QDs without any wetting layer, and therefore the QDs exhibit full 3D nano-scale confinement by the elimination of the wetting layer states. The approach opens up a large number of possibilities for bandgap engineering. Manipulating the shape, chemical composition and surroundings of the nanostructures is the key to tailor the energy level structure and wavefunctions in the dots.
The project is focused on the design and development of epitaxial growth of high-quality QD material for device applications employing the SAG approach and implementing the resulting material as a gain medium for laser devices. To form the mask for SAG, diblock copolymer lithography will be used . In order to transfer the pattern formed by self-organized processes in a copolymer to a thin glass layer an inductively coupled plasma reactive-ion etching process should be optimised. Work on the project also includes the theoretical estimation of electronic properties of the resulting QDs by applying packages developed on k·p electronic structure multiband equations and tight-binding models. Extraction of the strain field and energy level configuration of the QDs can be compared with transmission electron microscopy and optical measurements to form a closed loop of research.
The practical part of the research will be carried out in the state-of-the-art national clean room facility DTU Danchip.
 Thompson, M. G., Rae, A. R., Xia, M., Penty, R. V., and White, I. H., "InGaAs Quantum-Dot Mode-Locked Laser Diodes," IEEE Journal of Selected Topics in Quantum Electronics 15, 661 ( 2009).
 Kuech T.F. and Mawst L.J., “Nanofabrication of III–V semiconductors employing diblock copolymer lithography,” J. Phys. D: Appl. Phys. 43, 183001 (2010).
Candidates should have a master's degree in physics, nanotechnology, photonics engineering or a similar degree with an academic level equivalent to the master's degree in engineering. Candidates with experience in clean-room fabrication, optical characterization, semiconductor physics and photonics are encouraged to apply.
Moreover, the candidate shall have additional skills such as:
- Ability to work independently, to plan and carry out complicated tasks, and to be a part of a large, dynamical group
- Good communication skills in English, both written and spoken
- Familiarity with clean-room facilities is highly appreciated
Approval and Enrolment
The scholarships for the PhD degree are subject to academic approval, and the candidates will be enrolled in one of the general degree programs of DTU. For information about the general requirements for enrolment and the general planning of the scholarship studies, please see the DTU PhD Guide.
The assessment will be by Assistant Professor Elizaveta Semenova, Associate Professor Kresten Yvind and Professor Kristoffer Almdal.
Salary and appointment terms
Salary and appointment terms are consistent with the current rules for PhD degree students. The period of employment is 3 years.
The start date is flexible, but preferably in spring of 2014.
For further information please ask Assistant Professor Elizaveta Semenova, phone: +45 45 25 63 85, email: email@example.com, Associate Professor Kresten Yvind, phone: +45 45 25 63 66, email: firstname.lastname@example.org or Professor Kristoffer Almdal phone: +45 42 25 81 44, email: email@example.com
You can read more about Department of Photonics Engineering on www.fotonik.dtu.dk
The application must be received no later than March 15 2014 by using the online system at DTU. Applications must be submitted as one PDF file containing materials to be given consideration. Please open the link "apply for this job online“ and fill in the application form and attach the following documents:
- A letter motivating the application (cover letter).
- Curriculum vitae.
- Grade transcripts and BSc/MSc diploma - Excel sheet with translation of grades to the Danish grading system (see guidelines and excel spreadsheet here).
Candidates may apply prior to obtaining their master's degree, but cannot begin before having received it.
All interested candidates irrespective of age, gender, race, disability, religion or ethnic background are encouraged to apply.
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