Nonlinear charge transport in semiconductor nanostructures

Semiconductors have been established as models for complex spatio-temporal dynamics. Our group has a long-standing experience in modelling nonlinear and chaotic spatio-temporal pattern formation of charge transport. At present we are investigating the following nanostructures, which are the main focus of current research in semiconductor technology:
 

 

• Semiconductor superlattices consist of a periodic sequence of alternating layers of two different materials with different band gaps. By applying a DC voltage, complex spatio-temporal dynamics of the electron  distribution generated by the formation of electric field domains and self-generated current oscillations can be observed. We apply methods of chaos control on these oscillation by means of time delayed feedback. 

   

   

  Collaborations:

   

   

  • Prof. Dr. A. Wacker

    (Lunds Universitet, Schweden),

    A.-P. Jauho

    (Mikroelektronik Centret Lyngy, Dänemark): Quantentransporttheorie

  • Prof. Dr. M. Fromhold (University of Nottingham, UK)
  • Prof. Dr. L. Eaves

    (University of Nottingham, UK): Experiment

  • Prof. Dr. J. Kolodzey

    (University of Delaware, USA): Hochfrequenzoszillationen (exp.)

   

  • Prof. Dr. E. Gornik

    (Institut für Festkörperelektronik TU Wien);

    Transmission durch Übergitter (experimentell)

  • Prof. Dr. K. F. Renk

    (Universität Regensburg); Höchstfrequenz-Oszillationen (experimentell)

   

   

  
  

  
  

 

 

 

 

 

• Resonant tunneling structures, consist of a quantum well embedded between two potential barriers giving rise to bistable,  Z-shaped current-voltage characteristics. Lateral pattern formation vertical to the current flow leads to complex chaotic scenarios of breathing current filaments as well as trigger fronts. In order to stabilize unstable spatio-temporal patterns we use methods of time delayed feedback. 

   

  Collaborations:

   

   

  • Dr. P. Rodin

    (Ioffe Physico-Technical Institute St. Petersburg, Russia): Schaltfronten

  • Prof. Dr. S.W. Teitsworth

    (Duke University, NC, USA); Laterale Musterbildung in

    niederdimensionalen Halbleiterstrukturen (experimentell)

   

   

  
  

  
  

   

   

 

• Quantum-dot structures,

  where the carriers are fully confined. In many respects this resembles the situation in atomic physics, so that these structures can be considered as artificial atoms. Ensembles of self-assembled quantum dots embedded in a resonant tunneling structure exhibit strongly nonlinear transport behaviour (negatice differential conductivity) and unusual noise properties.

  Collaborations:

   

   

  • Prof. Dr. A. Wacker, Dr. P. Samuelsson (Lunds Universitet,Schweden)
  • Prof. Dr. R. J. Haug

    (Universität Hannover)

  • Prof. Dr. L. Eaves (University of Nottingham, UK)
  • Prof. Dr. T. Brandes (TU Berlin)