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HL: Halbleiterphysik

HL 44: II-VI Halbleiter IV

HL 44.8: Vortrag

Montag, 7. März 2005, 16:45–17:00, TU P-N201

Growth Optimization and Properties of Self-assembled CdSe/ZnSe Islands Formed by Low Temperature Epitaxy and In-situ Annealing — •S Mahapatra, G Astakhov, C Schumacher, U Bass, W Ossau, J Geurts, and K Brunner — EPIII, Physikalisches Institut, Universität Würzburg, Am Hubland, D-97074, Würzburg

Properties of CdSe quantum dots (QDs) on ZnSe, self assembled during MEE growth of 2-3 ML CdSe at 230^∘C and subsequent annealing in Se ambient between 310-340^∘C are compared with those of QDs grown by conventional MBE at 300^∘C. X-ray interference, photoluminescence (PL), AFM, and Raman spectroscopy have been used to determine the amount of CdSe, the exciton energies, size, and area-density of these QDs. In the former process, a transition from a streaky (2x1) RHEED pattern, after the growth of the CdSe layer, to a spotty one during annealing is indicative of SK-like 2D-3D transition. The low temperature growth suppresses intermixing of the group II species at the ZnSe-CdSe interface, thereby enabling strain relaxation by island formation during annealing. Despite a lower amount of incorporated CdSe (possibly due to desorption), PL peaks of these dots are remarkably red-shifted and broadened compared to the MBE grown samples. We discuss these effects in the context of intermixing, desorption, and strain relaxation by 3D island formation. Variation of growth and annealing parameters and their effects will also be presented.