Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 28: Optical properties
HL 28.6: Talk
Wednesday, March 28, 2007, 15:30–15:45, H14
Cathodoluminescence spectroscopy of point defects in AlN — •Barbara Bastek1, Frank Bertram1, Thomas Hempel1, Juergen Christen1, Armin Dadgar1,2, and Alois Krost1,2 — 1Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany — 2AZZURRO Semiconductors AG, Magdeburg, Germany
A set of AlN layers MOVPE grown on (111) Si-substrate is characterized by spectrally resolved cathodoluminescence (CL) microscopy at temperatures from 5K to 300K. The growth conditions were systematically changed: III-V-ratio, growth temperature (TG) and pressure. A clear correlation between the growth conditions and the luminescence intensity of four different defects in the samples is found and their thermalization is analyzed. In all samples a broad band occurs at 3.28eV which is assigned to the oxygen-DX-center. We observe a strong thermal activation of this defect, perfectly described by an Arrhenius-function yielding an activation energy of 9meV and a quenching energy of 85meV, respectively. For growth under extensive N-supply, this band competes with (D0,X) and a second defect band shows up at 4.6eV which we assign to the Al-vacancy. The intensity of VAL decreases monotonously with rising temperature and the Arrhenius-fit yields two quenching energies of 9meV and 55meV. In contrast, for moderate N-supply during growth VAL is completely gone and (D0,X) dominates the spectrum. At high TG a weak CL band appears at 3.91eV, which we tentatively assign to a Si-related DX-center accounting for the Si substrate. This defect shows a slight activation with rising temperature, however, the quenching dominates its temperature dependence.