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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 Al_xGa_1−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 Al_xGa_1−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).