We use optically detected resonance techniques, including optically detected magnetic resonance (ODMR) technique and optically detected cyclotron resonance (ODCR) technique, to study II-VI and III-IV semiconductor nanostructures, such as CdTe/Cd0.65Mg0.35Te quantum wells and GaAs/AlxGa1-xAs quantum wells. The principle of these two techniqes are quite similar. Transisitnos between spin sub-level or Landaul levels can be induced by microwave or far-infrared (FIR) laser. These transistions can directly or indirectly influece the photoluminenscence (PL) of the semiconductor nanostructures under study. By analysing the PL with and without the microwave or FIR laser ,many papermeters, such as effective masses of carriers, the mobility of the sample, g-factors, Zeeman-Splitting can be determined.
Fig. 1 shows the schematic of the ODMR setup. The sample is mounted in a 10 T optical cryostat and excitd by circularly polarized light. Polarization-resolved photoluminescence is dispersed in a spectrometer and recorded by a nitrogen-cooled CCD. The microwave is applied on the sample periodically. When the enegy of the micowave is equal to Zeeman splitting of electrons under certain magetic field, spin sub-level transistion can be induced, which results in the change of the PL. With this technique, the Zeeman splitting and electron g-factor can be determined.
We investigate transitions of semiconductor nanostructures which often lie in the energy range of a few meV. This corresponds to radiation in the far infrared regime with frequencies of a few THz. The detectors for far infrared light are not sensitive enough to allow direct absorption measurements. Therefore an indirect technique, the so called Optically Detected Resonance (ODR) technique is used to study the samples. Fig. 2 shows the experimental setup.
The recombination of carriers in a semiconductor structure generates the photoluminescence (PL) which depends on the properties of the sample (band gap, carrier concentration, temperature, magnetic field…). Changes to these properties are also reflected in the photoluminescence signal. Observing the PL with and without FIR radiation, at different temperatures and magnetic fields reveals details of the internal structure and other sample properties. It is possible to determine the effective masses of carriers, the mobility of the sample, g-factors, Zeeman-Splitting and to study charged excitons (trions).
Current Offers For Bachelor-, Master- or PhD-Theses
We offer Bachelor- and Master-theses in relation to the ongoing research. Feel free to ask someone of the team for more information.
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Location & approach
The campus of TU Dortmund University is located close to interstate junction Dortmund West, where the Sauerlandlinie A 45 (Frankfurt-Dortmund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is "Dortmund-Eichlinghofen" (closer to Campus Süd), and from B 1 / A 40 "Dortmund-Dorstfeld" (closer to Campus Nord). Signs for the university are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dortmund.
To get from Campus Nord to Campus Süd by car, there is the connection via Vogelpothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at Campus Nord and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.
TU Dortmund University has its own train station ("Dortmund Universität"). From there, suburban trains (S-Bahn) leave for Dortmund main station ("Dortmund Hauptbahnhof") and Düsseldorf main station via the "Düsseldorf Airport Train Station" (take S-Bahn number 1, which leaves every 20 or 30 minutes). The university is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duisburg.
You can also take the bus or subway train from Dortmund city to the university: From Dortmund main station, you can take any train bound for the Station "Stadtgarten", usually lines U41, U45, U 47 and U49. At "Stadtgarten" you switch trains and get on line U42 towards "Hombruch". Look out for the Station "An der Palmweide". From the bus stop just across the road, busses bound for TU Dortmund University leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dortmund main station to the stop "Dortmund Kampstraße". From there, take U43 or U44 to the stop "Dortmund Wittener Straße". Switch to bus line 447 and get off at "Dortmund Universität S".
The AirportExpress is a fast and convenient means of transport from Dortmund Airport (DTM) to Dortmund Central Station, taking you there in little more than 20 minutes. From Dortmund Central Station, you can continue to the university campus by interurban railway (S-Bahn). A larger range of international flight connections is offered at Düsseldorf Airport (DUS), which is about 60 kilometres away and can be directly reached by S-Bahn from the university station.
The H-Bahn is one of the hallmarks of TU Dortmund University. There are two stations on Campus Nord. One ("Dortmund Universität S") is directly located at the suburban train stop, which connects the university directly with the city of Dortmund and the rest of the Ruhr Area. Also from this station, there are connections to the "Technologiepark" and (via Campus Süd) Eichlinghofen. The other station is located at the dining hall at Campus Nord and offers a direct connection to Campus Süd every five minutes.
The facilities of TU Dortmund University are spread over two campuses, the larger Campus North and the smaller Campus South. Additionally, some areas of the university are located in the adjacent "Technologiepark".