Superfluorescence of Ion Beam Synthesized Dense-Packed Embedded CdSe Nanoclusters

Abstract

Dense-packed embedded semiconductor quantum dot (QD) layers with a multimodal size distribution are representing new types of QD solids. Their optical and electronic properties are modified due to dipole-dipole interactions and tunneling effects. In this work sequential high dose ion implantation of Cd and Se and subsequent thermal treatment is used to synthesize QD assemblies with the required structural properties in the surface near region of 500 nm thick thermally grown SiO₂ on Silicon. We used cw photoluminescence (PL) to study PL-yield as a function of pump laser power at low temperatures for different various stoichiometries and annealing conditions. In these embedded QD assemblies of mixed size distribution we detected a promising non-linear increase of the PL-intensity with laser excitation power. The exponents evaluated are maximal for implanted Cd:Se-dose ratios between 0.8 and 1.0. The power law dependence of the PL-yield on pump laser power will be discussed in context with electronic energy transfer between dense-packed QD's of different size, implanted dose ratios and postimplantation thermal treatment conditions.