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Research focus:  

C 3-Professur für Technische Physik
Am Hubland, 97074 Würzburg
Url: http://x

Scientific members:


   Scientific assistants:

Research foci (and basic equipment-based research projects):
The research activities of this group focus on the realization of low-dimensional model systems based on layered semiconductor structures and the investigation of their electronical properties by the Fourier transform spectroscopy. In the center of interest are quasi-twodimensional as well as mesoscopic and microscopic structures with reduced dimensionality. In the process of realizing lowdimensional model systems well known techniques of lateral microstructering are applied. Structures with sizes on the micrometer and nanometer scale are fabricated by lithographic processes, etching and metallization techniques. Information about the electronical properties of the model systems is gained by frequency-dependent investigations of their elementary excitations at low temperatures and high magnetic field strengths. Via studies of inta- and interband excitations a clarification of the electronic band structure of semiconductor materials with potential technical applications is pursued. The more basic research oriented aspect of the experiments deals with open questions regarding influences of many-body effects, the carrier spin and the electron-phonon interaction. Presently, the applied material systems are III-V and mercury based II-VI compounds that were grown by molecular beam epitaxy.

The cyclotron resonance is an important elementary electronic excitation to characterize carrier systems with quasi-twodimensional properties. Investigations were performed here on high-mobility electron inversion-layers in GaAs with the attempt to clarify the influences of the integral and fractional quantum Hall effects. In addition, localization phenomena were studied in intentionally disordered GaAs single heterostructures.

?Filling-factor-dependent electron correlations observed in cyclotron resonance?
M. Manger, E. Batke, R. Hey, K. J. Friedland, K. Köhler, and P. Ganser
Phys. Rev. B 63, 121203 (2001).

?Cyclotron resonance at fractional Landau-level fillings?
M. F. Manger, E. Batke, and W. Wegscheider
Solid State Commun. 120, 463 (2001).

?Percolation of quantum Hall droplets in intentionally disordered GaAs-GaAlAs heterojunctions?
K. Buth, M. Widmann, U. Merkt, E. Batke, and K. Eberl
Proc. 14th EP2DS, Prag, 2001.

The interaction of longitudinal optical phonons with the elementary electronic excitations of layered semiconductor structures so far has not been experimentally investigated intensively. To gain a better insight in the electron-phonon interaction in layered semiconductor structures we investigated confined and interface phonons in short-period AlGaAs-GaAs superlattices with a new experimental approach, the grating coupler induced infrared spectroscopy.

"Grating-coupler excited interface phonons in GaAs/AlGaAs superlattices"
A. Milekhin, M. Rösch, E. Batke, K. Köhler, and P. Ganser
Solid State Commun. 112, 387 (1999).

"Infrared and Raman studies of confined and interface optical phonons in short-period GaAs/AlAs superlattices with a grating coupler"
A. Milekhin, M. Rösch, E. Batke, D. R. T. Zahn, K. Köhler, P. Ganser, V. Preobrazhenski, and B. Semyagin
J. Vac. Sci. Technol. B 17, 1738 (1999).

Investigations of the electronic band structure of mercury-based II-VI heterostructures were performed in particular on HgSe epitaxial layers and HgTe quantum wells.

"Magneto-absorption of modulation doped HgTe quantum wells"
A. Pfeuffer-Jeschke, M. von Truchseß, C. R. Becker, K. Ortner, E. Batke, and G. Landwehr
Proc. 9th International Conference on Narrow Gap Semiconductors, Berlin, 1999.

"Magneto-absorption and magneto-transport in mercury selenide?
M. von Truchseß, A. Pfeuffer-Jeschke, X. C. Zhang, C. R. Becker, G. Landwehr, and E. Batke
Proc. 9th International Conference on Narrow Gap Semiconductors,
Berlin, 1999.

"Electronic band structure of HgSe from Fourier transfom spectroscopy"
M. von Truchseß, A. Pfeuffer-Jeschke, C. R. Becker, G. Landwehr,and E. Batke
Phys. Rev. B 61, 1666 (2000).

Preparation ans semiconductor technology:

Preparation chamber for lithographic processes, realization of semiconductor contacts and wet chemical etching
Lithographic structuring of semiconductor surfaces (structure size > 1 mm)
Optical holography for the realization of simple structures in the sub micrometer regime
Try etching of photoresist layers and semiconductor surfaces
Metallization of semiconductor surfaces

Characterization and spectroscopic tools:

Fourier transform spectroscopy in a frequency regime from the far-infrared up to the ultraviolet
Cryomagnet systems (magnetic field regime up to 17 Tesla)
Temperature inserts for experiments in the regime from 400 mK up to 300 K
Helium cryostats


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