Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 47: GaN: preparation and characterization I
HL 47.10: Vortrag
Donnerstag, 28. Februar 2008, 16:30–16:45, EW 202
Spatially and spectrally resolved cathodoluminescence of hexagonal GaN pyramids covered by InGaN single quantum wells — •S. Metzner1, B. Bastek1, F. Bertram1, T. Hempel1, J. Christen1, M. Jetter2, T. Tsifotidis2, and P. Michler2 — 1Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany — 2Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen, Stuttgart University, Germany
Masking with polystyrene micro spheres, self organized hexagonal GaN pyramids terminated by the six {1101} facets were selectively grown by metal-organic vapor phase epitaxy. An InGaN single quantum well (SQW) capped with a GaN layer was deposited on top. The spatially averaged cathodoluminescence (CL) spectrum shows an intense (D0,X) line from GaN and a broad emission band between 2.0 - 2.6 eV originating from the InGaN SQW. The CL from the masked area reveals a blue-shifted (D0,X) GaN emission at 3.4925 eV (FWHM = 5.8 meV) corresponding to a compressive stress of 0.8 GPa. In contrast, the (D0,X) GaN emission of the pyramid facets is more intense, broadened, and red-shifted with respect to fully relaxed GaN. This red-shift decreases from base (3.4398 eV) to top of the pyramids by about 20 meV, indicating strain relaxation and strong local impurity incorporation at the slower growing facets. The InGaN luminescence exclusively emitted on the pyramids shows a monotonous blue-shift of about 100 meV from base (2.3542 eV) to top of the facets. Smaller SQW thickness and/or lower In content can explain the observed blue-shift towards the tip. The impact of polarization fields further enhances this effect.