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CdSe Quantum Islands in ZnSe: A New Approach

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This paper provides a general overview of the current status of self-organization of quantum islands in the II-VI semiconductor system, focusing on Cadmium Selenide CdSe embedded in Zinc Selenide ZnSe, and also discusses the possibilities opened by a modification of the standard growth technique. In molecular beam epitaxy, the authors have substituted the generally used Cd-elemental source with a Cadmium Sulfide CdS compound source. The sulfur is usually not included in the growing layer. However, its presence can be surfactant-like while the elevated Cd-temperature of the dissociated CdS leads to changed thermodynamic conditions on the growth front. Using migration enhanced epitaxy, nearly perfect quantum wells with respect to lateral homogeneity can be obtained by suppressing the inherent Cd segregation and clustering. These processes are generally responsible for the formation of small islands SI lateral diameter 3-5 nanometers even when not attempting to grow island-like structures. The suppression of these SI was a first step in gaining control over the island formation. Larger islands with central Cd concentrations above 40 are of greater interest for device applications since a population at room temperature is necessary. In particular, high-density systems are required. Using the modified growth mode, well-correlated, stacked island systems were obtained. The outstanding structural and optical properties of these island systems are discussed in detail in this paper. The absence of a closed wetting layer in the CdSeZnSe system and the appearance of island-like structures, even at submonolayer nominal deposition, further corroborate the assumption that island formation does not readily occur in a standard Stranski-Krastanow growth mode, which is assumed for InAsGaAs. 8 figures, 45 refs.

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  • Solid State Physics
  • Crystallography

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