Prof Fred Pollak, Tues 3 Nov: Stress Effects- Microstr. Optical Props.

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1 total messages Started by Alfred M. Kriman Wed, 28 Oct 1992 19:45

Author: Alfred M. Kriman
Date: Wed, 28 Oct 1992 19:45

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Physics Department Seminar: 
       +----------------------------------------------------------------+
       |   Title:   "External and/or Internal Stress Effects on the     |
       |          Optical Properties of Semiconductor Microstructures"  |
       |                                                                |
       | Speaker: Prof. Fred Pollack                                    |
       |      of: Physics Dept., Brooklyn College of CUNY               |
       +----------------------------------------------------------------+

    Location: Room 219 of Fronczak Hall, Amherst Campus of SUNYAB

        Date: Tuesday, November 3, 1992

        Time: 3:45 PM  (Refreshments 3:30 PM, room 245)

 Information: SUNYAB Department of Physics and Astronomy
              Dept. Office: (716) 645-2017  FAX: (716) 645-2507

_A_B_S_T_R_A_C_T:
      The application of an external and/or internal homogeneous strain
   (hydrostatic or uniaxial) in a solid produces changes in the lattice
   parameter (hydrostatic and uniaxial) and in the uniaxial case, the
   symmetry of the material.  These in turn create significant changes in
   the electronic band structure as well as the vibrational modes.  For
   electronic states, energy gaps are altered and, in some cases,
   degeneracies are removed.  Effective masses are influenced by variations
   in energy gaps as well as changes in matrix elements.  Since, in general,
   uniaxial stress changes the symmetry of the material, polarization
   effects are produced which are not present in the unstrained sample.
      This talk will review the influence of homogeneous strains, external
   and/or internal, on the electronic and optical properties of semiconductor
   microstructures such as epilayers, quantum wells and superlattices.  In
   particular, the effects of large external compressive stress _T on the
   interband (intersubband) transitions of two systems will be discussed in
   detail.  These are (a) _T || [100] on biaxially strained bulk GaAs and
   two GaAs/AlGaAs single quantum wells (SQW) grown on (001) Si and
   (b) _T || [100] and _T || [110] (piezoelectric effect) on (001)
   GaAs/AlGaAs SQW structures.  The relation between hydrostatic pressure
   and uniaxial stress measurements will be explored.

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