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     COLLOQUIUM OF THE COMPUTATIONAL MATERIALS SCIENCE CENTER
       AND THE DEPARTMENT OF COMPUTATIONAL AND DATA SCIENCES
                         (CSI 898-Sec 001)
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   Auger recombination and its suppression in nanoscale semiconductors

                           Roman Vaxenburg
           
 Computational Material Science Center,George Mason University, Fairfax, VA 
                                 and
              Naval Research Laboratory, Washington D.C.

Nonradiative Auger recombination is an energy dissipation mechanism in which 
the recombination energy of an electron-hole pair, instead of being emitted 
as a photon, is transferred to another charge carrier and is eventually lost 
as heat. If efficient enough, the Auger process can considerably reduce the radiative 
efficiency of semiconductor materials, therefore complicating their application 
as light emitters. As a consequence of quantum confinement, in nanoscale 
semiconductor systems such as quantum wells or quantum dots, the Auger 
recombination is greatly enhanced and is able to interfere with the radiative 
recombination.

Here we present a theoretical study of the nonradiative Auger recombination 
processes in III-V quantum well light-emitting diodes (LEDs). The performance 
of these LEDs is known to steadily decrease with increasing driving current 
and the origin of this efficiency droop phenomenon is still debatable. Our 
calculations show that the Auger recombination can be efficient enough in 
these materials and that it can be the source of the efficiency droop. Further, 
we propose a strategy to suppress the confinement-enhanced Auger recombination 
by controllable modification of the confining potential shape. We apply this 
approach to both polar and nonpolar variants of the III-V quantum well LEDs and 
we demonstrate an appreciable suppression of the Auger recombination and consequent 
improvement of light-generation efficiency in these materials.

                          November 9, 2015
                               4:30 pm
                    Exploratory Hall, room 3301 
                          Fairfax Campus

Refreshments will be served at 4:15 PM.
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Find the schedule at http://www.cmasc.gmu.edu/seminars.htm