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HL: Halbleiterphysik
HL 13: III-V Halbleiter II
HL 13.6: Vortrag
Freitag, 4. März 2005, 16:15–16:30, TU P-N202
Defect related optical transitions in AlN bulk crystals — •Martin Albrecht1, Klaus Irmscher1, Matthias Roßberg1, Thilo Remmle1, Jürgen Wollweber1, and Axel Hoffmann2 — 1Institut für Kristallzüchtung, Max-Born-Strasse 2, 12489 Berlin — 2Institut für Festkörperphysik, TU Berlin, Hardenbergstrasse 36 10623 Berlin
Optical transitions in epitaxial AlN layers and bulk crystals are in general dominated by a broad luminescence band ranging from 4eV - 2eV. This luminescence band has been attributed to a variety of point defects (e.g. N-vacancies, Al vacancies and interstitials, ON) or defect complexes (especially VAl - ON). Youngman and Harris showed, that a red shift of this band could be related to an increasing oxygen content. In this paper we study by means of optical spectroscopy, electro-paramagnetic resonance and transmission electron microscopy AlN bulk crystals grown by the sublimation method. The crystals were grown in the temperature range between 1900∘C and 2100∘C in BN crucibles. They are either hexagonal platelets or single crystalline boules of 12x3x2mm size grown along the c-axis. We find defect related bands at 3.45 eV, 3.0eV, 2.0 eV and 1.6 eV. A detailed study based on temperature and excitation dependent cathodoluminescence, time resolved photoluminescence and photoluminescence excitation is performed to analyse the physical nature of the defect related optical transitions