Dresden 2014 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Nitrides: Optical characterization

HL 13.1: Talk

Monday, March 31, 2014, 11:15–11:30, POT 251

Nano-scale characterization of InGaN/GaN core-shell micropillars using helium temperature STEM-CL — •Marcus Müller¹, Sebastian Metzner¹, Anja Dempewolf¹, Gordon Schmidt¹, Peter Veit¹, Frank Bertram¹, Jürgen Christen¹, Steven Albert², Ana María Bengoechea-Encabo², Miguel Ángel Sánchez-Garcia², and Enrique Calleja² — ¹Institute of Experimental Physics, OvGU Magdeburg, Germany — ²ISOM and Departamento de Ingeniería Electrónica, UP Madrid, Spain

In this study we report on the approach of combining top-down and the bottom-up processes to fabricate ordered InGaN/GaN core-shell micropillars by plasma-assisted molecular beam epitaxy. Direct comparison of the cross-section scanning transmission electron microscopy image of a single InGaN/GaN core-shell micropillar with the simultaneously recorded panchromatic cathodoluminescence (CL) mapping at 15 K reveals the highest CL intensity from the thick InGaN cap region and from the InGaN side walls. The CL peak wavelength image exhibits a dominating emission from the GaN near band edge at 359 nm as well as the yellow band at 560 nm from the center of the micropillar. On the side facets we observe an InGaN CL peak at 407 nm. In contrast, the upper part of the micropillar emits a broad luminescence band between 510 nm and 640 nm which can be attributed to different In compositions and strain conditions compared to the side facets. Furthermore, a red shift of the InGaN luminescence in both InGaN regions is observed indicating a gradual increase of the In composition during the growth due to the lattice pulling effect.