Silicon nitride engineering: Role of hydrogen-bonding in Ge quantum dot formation

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_xN_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_xN_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.