Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 45: Group-III-Nitrides: Optical Properties II
HL 45.7: Vortrag
Mittwoch, 24. März 2010, 16:15–16:30, H15
Optical and structural investigations of pendeo-epitaxial AlGaN layers by spectrally resolved cathodoluminescence microscopy — •G. Schmidt1, B. Bastek1, T. Hempel1, F. Bertram1, J. Christen1, V. Küller2, A. Knauer2, F. Brunner2, H. Rodriguez2, M. Weyers2, and M. Kneissl2 — 1Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany — 2Ferdinand-Braun-Institut für Höchstfrequenztechnik, Berlin, Germany
The ternary alloy AlGaN is a promising candidate for optoelectronic devices emitting in the deep UV. However, due to the large lattice and thermal mismatch, AlGaN layers grown on sapphire exhibit a high density of dislocations. In order to reduce this density AlGaN layers have been grown by pendeo-epitaxy. For this approach an AlN layer is directly grown on sapphire and subsequently patterned, resulting in a stripe structure parallel to [1010] with a trench width of 1.9µm and a ridge width of 1.1µm. The pattern was overgrown by a fully coalesced MOVPE AlGaN layer. We present the microscopic optical properties of the pendeo-epitaxial AlGaN layers. The spatially integrated cathodoluminescence (CL) spectrum exhibits two dominant peaks at 3.939eV and 4.326eV, respectively. Spatially resolved CL proved a correlation between the wavelength distribution and the trench pattern. The high energetic luminescence originates from the areas above the AlN ridges and the low energetic intensity from the area above the trenches, suggesting local different Al incorporation. Furthermore, the strain relaxation in growth direction is imaged by cross-sectional CL.