Berlin 2008 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 47: GaN: preparation and characterization I
HL 47.12: Talk
Thursday, February 28, 2008, 17:00–17:15, EW 202
Cathodoluminescence Microscopy of GaN Nanopyramids grown on Si(111) — •F. Bertram1, S. Metzner1, J. Christen1, H. Tang2, J. Lapointe2, and J.A. Bardwell2 — 1Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany — 2nstitute for Microstructural Sciences, National Research Council Canada, Ottawa, Canada
A 10 nm thick AlN buffer MBE grown on Si(111) was patterned into an array of hexagonal pads with openings from 0.5 to 1.5 um. The subsequent GaN overgrowth was carried out in both, the vertical and the lateral direction forming distinct GaN nanopyramids terminated by {10-12} side facets. The GaN pyramids were covered with an InGaN quantum well for the purpose to form an InGaN quantum dot at the very top. A lateral pyramid size of about 1 um and a height of about 800 nm is obtained independent from the mask size. The spatially integrated cathodoluminescence (CL) spectrum of a single pyramid at 5 K exhibits multiple sharp emission lines over a wide spectral range from 357 to 500nm. No CL emission was observed outside the pyramids. Intensity mappings across the pyramids show clear 6 fold symmetry. The intensity drops significantly at the edges of the pyramid. The top region of the pyramids exhibit a bright hexagonally shaped contrast dominated by GaN emission. On the contrary, the InGaN luminescence is very intense at the base of the pyramids. The InGaN intensity decreases and the emission blue-shifts from 405 to 375nm, from the base to the top of the pyramid.