3D SiGe QUANTUM DOT CRYSTALS: STRUCTURAL CHARACTERIZATION AND ELECTRONIC COUPLING

We report on the growth of SiGe quantum dot crystals which are realized by depositing Ge on a two-dimensionally pit-patterned Si substrate and subsequent growth of Si spacer and Ge island layers. Lateral periods of 100 nm are obtained by employing deep UV lithography using synchrotron radiation. The vertical period of the typically 10 period dot superlattices was of the order of 10 nm. Ordering of the islands was investigated by atomic force microscopy as well as by high resolution x-ray diffraction studies. From the quantitative evaluation of the x-ray diffraction data a mean Ge content of about 60% in the quantum dots was obtained and an rms. deviation from ideal lattice sites of about 3 nm was found. A simulation of the eigenenergies based on the nextnano(3) simulation package was used to interpret the measured photoluminescence data.