Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 16: Quantum dots and wires: Optical properties I

HL 16.8: Talk

Monday, February 25, 2008, 16:00–16:15, ER 164

Optical properties of InGaN quantum dot stacks — •Joachim Kalden, Henning Lohmeyer, Kathrin Sebald, Thomas Meeser, Jürgen Gutowski, Christian Tessarek, Stephan Figge, and Detlef Hommel — Institute of Solid State Physics, University of Bremen, P.O. Box 330 440, D-28334 Bremen, Germany

In the blue to UV spectral region InGaN quantum dots (QDs) are an up-and-coming material system. Beside research concerning the fundamental properties of these QDs, it is necessary to increase the QD density for laser applications. Hence samples with multiple QD layers are characterized to investigate the influence of stacking on the optical properties. Therefore, we compare micro-photoluminescence (µ-PL) measurements of single and stacked QD layers grown by metal-organic vapor phase epitaxy. The optical emission properties are discussed with respect to polarization and temperature, respectively. In contrast to the single QD layer, no sharp emission lines can be found for the unstructured stacked layers. Their ensemble PL band is easily traceable up to room temperature. To prove the QD origin of these samples mesa structures are prepared by focused-ion-beam etching. As expected, for decreasing mesa diameter the broad emission band of the QD ensemble splits up and individual sharp emission lines can be observed. Their characteristics are comparatively discussed with the results achieved from the single QD layer samples. Additionally, gain measurements on single QD layers and QD stacks will be discussed.