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 [1]

    (Lunds Universitet, Schweden) [2],

    A.-P. Jauho [3]

    (Mikroelektronik Centret Lyngy, Dänemark): Quantentransporttheorie

  • Prof. Dr. M. Fromhold [4] (University of Nottingham, UK) [5]
  • Prof. Dr. L. Eaves [6]

    (University of Nottingham, UK [7]): Experiment

  • Prof. Dr. J. Kolodzey

    (University of Delaware, USA [8]): Hochfrequenzoszillationen (exp.)

   

  • Prof. Dr. E. Gornik

    (Institut für Festkörperelektronik TU Wien [9]);

    Transmission durch Übergitter (experimentell)

  • Prof. Dr. K. F. Renk [10]

    (Universität Regensburg); Höchstfrequenz-Oszillationen (experimentell)

   

   

  
  

  
  

 

 

 

 

 

• Resonant tunneling structures [11], 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 [12]

    (Ioffe Physico-Technical Institute St. Petersburg, Russia) [13]: Schaltfronten

  • Prof. Dr. S.W. Teitsworth [14]

    (Duke University, NC, USA) [15]; Laterale Musterbildung in

    niederdimensionalen Halbleiterstrukturen (experimentell)

   

   

  
  

  
  

   

   

 

• Quantum-dot structures [16],

  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 [17], Dr. P. Samuelsson [18] (Lunds Universitet,Schweden [19])
  • Prof. Dr. R. J. Haug

    (Universität Hannover [20])

  • Prof. Dr. L. Eaves [21] (University of Nottingham, UK) [22]
  • Prof. Dr. T. Brandes [23] (TU Berlin) [24]