We report local nitride-stressor engineering in combination with quantum-size tunability in Ge quantum dots (QDs) for tailoring photoluminescence (PL) wavelength and exciton lifetime. Spherical-shaped Ge QDs with tunable diameters ranging from 25–90 nm embedded within layers of thermally-grown SiO2 and chemical-vapor-deposited Si3N4 were fabricated by thermal oxidation of lithographically-patterned poly-Si0.85Ge0.15 pillars on top of buffer layers of SiO2 and Si3N4, respectively, in a self-organization approach. The effects of local stressors and quantum confinement on the strain and optical properties of Ge QDs were systematically investigated using Raman and PL measurements. We observed that when Ge QD diameter gets smaller than 60 nm, quantum confinement sets in and has a predominant influence on PL wavelength and exciton lifetime. Our self-organized Ge QD/Si3N4 system provides a generic building block for the fabrication of active photonic devices on Si3N4 platform.

We report the lowering of the formation temperature of spherical-shaped Ge quantum dots (QDs) to 850 • C from our previously-reported 900 • C. This large reduction in QD formation temperature was achieved via the use of a hydrogenated, plasma-enhanced chemical-vapor deposited (PECVD) silicon nitride (SiN). The exquisite interplay between H, Ge, Si and O interstitials, controlling QD formation during the thermal oxidation of poly-SiGe layers deposited over PECVD-Si x N y : H, is further explored in order to understand the underlying mechanisms. We have experimentally observed that the high hydrogen content of the PECVD-Si x N y : H facilitates the lower-temperature (850 • C) oxidation of the nitride layer, while simultaneously being able to generate smaller diameter, fully coalesced Ge QDs within. Such heterostructures of SiN coupled-Ge QDs are a fundamental building block for the ultimate fabrication of active SiN-based Ge photonic devices. Keywords Si 3 N 4 , germanium, quantum dot, hydrogen

Effects of a cesium ion beam on GaAs. InP, and Si (7) On InP, on which very pronounced sprouting ofInP crystals from ion bombardment with argon and xenon was observed (to be published), the use of cesium instead of a noble gas was found to reduce (though notprevent) sprouting. It is conduded that the presence of cesium can have a subduing influence on microtopography development.The observations show cesium to be an excellent decorating material for mapping defect distributions by SEM in the vicinity of sputtered structures.