Growth and Device Integration of Single Site-Controlled Quantum Dots
Jul 31, 2012
from 02:00 PM to 04:00 PM
|Where||ENGR. IV Bldg., Tesla Rm. 53-125|
|Contact Name||Prof. Diana Huffaker|
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Technische Physik, Universität Würzburg, Germany
Single semiconductor quantum dots (QDs) are very attractive candidates to control charge and spin carries at the quantum level and therefore are very promising for applications in fields ranging from nanoelectronics over nanophotonics to spintronics. One of the major challenges regarding the scalable fabrication of single QD based devices is however the precise control of the QD position within device structures. Within this talk, site-controlled growth of QDs on pre-patterned nanohole templates for integration of into nanoscale devices will be discussed. By combining this growth technique with a process capable of accurately aligning QDs relatively to subsequently fabricated device structures, several interesting devices could be fabricated based on positioned QDs. For instance, cavity enhanced emission of single site-controlled QDs that were deterministically placed within photonic crystal or micropillar cavities have been demonstrated. Single photon emission of a coupled QD-resonator system has been proven by photon auto-correlation measurements, for both optical and electrical excitation, thus underlining the promise of the devices for quantum communication technologies. Stacking of site-controlled QDs is applied to improve the optical quality of the QDs, and best single QD linewidths for above band gap excitation down to 25 µeV have been obtained, which is competitive to results on self-assembled QDs. The current status of research on the site-controlled QD topic will be summarized focusing on results obtained in our group, and future directions and challenges will be outlined.
Dr. Sven Höfling studied Applied Physics at the University of Applied Science, Coburg, Germany. He received the Diploma from the University of Applied Science Coburg, Coburg, Germany, in 2002, for his investigations of InGaN-based blue, green and white light emitting devices at the Fraunhofer Institute of Applied Solid State Physics (IAF) in Freiburg, Germany. In 2003 he joined the department of Technische Physik at Universität Würzburg, Germany. There he worked on the design, growth, fabrication and characterization of single mode emitting quantum cascade lasers for which he received the doctorate degree with distinction. Since 2006, he leads the Optoelectronic Materials and Devices Group and he supervises the molecular beam epitaxial growth at the Microstructure Laboratory using various molecular beam epitaxy systems being customized for the growth of III-V based semiconductors based on the GaAs-, InP-, Ga(N)P- and GaSb-based material system. In 2010, he stayed as a short term visiting scholar at Stanford University, USA, where he is currently for another visiting scholar term. His current research interests include the design, fabrication, and characterization of low-dimensional electronic and photonic nanostructures, including quantum wells and quantum dots, site-controlled quantum dots, high-electron-mobility structures, high-quality-factor photonic cavities, and semiconductor lasers.