Münster 1999 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 24: III-V Halbleiter
HL 24.5: Vortrag
Mittwoch, 24. März 1999, 16:00–16:15, BOT
Near-band gap CuPt order-birefringence in AlxGa1−xInP (0<x<1) — •Mathias Schubert1, Tino Hofmann1, Bernd Rheinländer1, Ines Pietzonka2, Torsten Saß2, and Volker Gottschalch2 — 1Fakultät für Physik und Geowissenschaften, Halbleiterphysik, Linnestraße 5, D-04103 Leipzig — 2Fakultät für Chemie und Mineralogie, Halbleiterchemie, Linnestraße 3, D-04103 Leipzig
We report explicitely and for the first time the order-induced birefringence
in the near-band-gap spectral range (0.75 eV to 2.75 eV), together with the
zone-center transition energies of CuPt-ordered AlxGa1−xInP as
a function of composition and degree of ordering. A comprehensive set
of polarimetric techniques consisting of generalized variable angle
spectroscopic ellipsometry, cross-polarized dark-field spectroscopy,
and modulated cross-polarized reflectance difference spectroscopy
is used to determine precisely the room-temperature dielectric
functions for polarizations parallel and perpendicular to the ordering
direction from a large set of samples grown by MOVPE. We treat the
observed birefringence as "chemical stress" induced piezo-birefringence.
We find that parabolic band approximations and selection rules for the
zone-center transitions suffice for excellent modelling of the
order birefringence. All parameters in the quasi-cubic perturbation model
can be fitted. Our results allow critical comparison with recent theoretical
predictions by Wei and Zunger (Phys.Rev. B57 (1998) 8983).