Cel
A novel set of experiments will be carried out making use of the bandstructure engineering possibilities in semiconductor superlattice structures (GaAs/GaAlAs and Si/Ge) to develop the basis for new sources in the THz regime. By the introduction of a special potential modulation through the successive growth of different materials, the electronic bandstructure will be modified and sub-bands formed with appropriate energy splitting. Since optical phonon emission is a limiting process, structures will be designed which use injection energies below the optical phonon energy.
Two basic approaches to generate population inversion will be applied. First, a new approach will use the injection of ballistic carriers into a periodic potential with a large period. A Smith-Purcell-type radiation will be generated. The frequency can be set by the modulation period and tuned by the carrier velocity. Second, electrical carrier heating will be used to induce population inversion. Steaming notion in two-dimensional electron and hole systems as well as different bandstructure adjustments by growth and external field will be applied to influence electronic lifetimes in different sub-band levels. Population inversion between sub-bands in quantum wells or between mini-bands in superlatives is the basic requirement to achieve a coherent radiation source.
The goal of this project is the study of the key processes which will enable coherent and tuneable THz sources to be developed which can be operated at d.c. conditions.
Temat(-y)
Zaproszenie do składania wniosków
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1040 Wien
Austria