Regensburg 2000 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 36: Quantenpunkte (Herstellung und Charakterisierung)

HL 36.3: Vortrag

Donnerstag, 30. März 2000, 16:30–16:45, H13

Quantum island formation in CdS/ZnS heterostructures grown by MOVPE — •C. Meyne¹, U. W. Pohl¹, W. Richter¹, M. Straßburg¹, A. Hoffmann¹, V. Türck¹, S. Rodt¹, D. Bimberg¹ und D. Gerthsen² — ¹Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin — ²Laboratorium für Elektronenmikroskopie der Universität Karlsruhe

Type I aligned CdS/ZnS heterostructures with a mismatch of -7% are of interest for excitonic quantum confined emission in the deep blue and near UV spectral range. Emission of three-dimensionally confined excitons has been already reported in a micro-photoluminescence study of monolayer-thin CdS/ZnS single quantum wells. However, localisation was shown to originate from thickness fluctuations in the monolayer range [1]. We prepared CdS/ZnS heterostructures with single and stacked monolayer-thick CdS layers consisting of clearly resolved flat quantum islands. Cross-section high resolution transmission electron microscopy (HRTEM) of a single CdS layer embedded in ZnS shows coherently strained CdS islands. These islands act as localisation centers for excitons. Evidence for three-dimensional exciton confinement is given by ultra-sharp emission peaks found in cathodoluminescence (CL) spectra which are excited in a small area of about 0.4 µm diameter. Optical gain originating from localised excitons was found up to high excitation intensities with only minor saturation.

[1] U. Woggon et al., phys. stat. sol. (b) 206 (1998) 501.