[Phys-seminars] 2011-02-21 Condensed Matter Seminar

manassen at bgu.ac.il manassen at bgu.ac.il
Wed Feb 16 09:26:23 IST 2011


Condensed Matter Seminar

  DATE: 21-02-2011

  TIME: 11:30am (Mon)

  PLACE: Physics building (#54) room 207

TITLE: 
Effects of In-Plane Uniaxial Stress on the Optical Properties of GaN/AlN Self-Assembled Quantum Dots



SPEAKER: 
Dr. Ofer Moshe, Dept of Physics, BGU

ABSTRACT/COMMENTS:
    The growth and optical properties of III-Nitride-based wurtzite
 self-assembled quantum dots (QDs) have attracted much attention
 in the past decade. In this work, GaN/AlN QDs were grown by the
 Stranski-Krastanov method on Si(111) using molecular beam epitaxy.
 During the subsequent cooling from growth temperatures, the thermal
 expansion coefficient mismatch between the Si substrate and GaN/AlN
 film containing vertically stacked QDs leads to an additional
 biaxial tensile stress in the III-nitride film, which we have
 modified to examine the electronic and optical properties under
 various in-plane stress configurations. The results show that a
 selective control of the in-plane stress also enables a local
 control of the polarized luminescence from ensembles of QDs.
 Localized cathodoluminescence (CL) spectroscopy of the QDs
 exhibits emissions from both the ground and excited states, whose
 relative contributions depend on the level of excitation and
 temperature. We have examined these emissions using spectrally,
 spatially, and temporally resolved CL with polarization detection.
 The effects of screening of the polarization field in the QD,
 state-filling, changes in the optical polarization anisotropy and
 lifetime with varying excitation were studied experimentally and
 modeled with a self-consistent 6x6 k.p calculation method.



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