Reconfigurable Germanium Quantum-Dot Arrays for CMOS Integratable Quantum Electronic Devices

The amazing world of self-organized Ge quantum dots for Si photonics on SiN platforms

“…Our extensive experimental observations show that the Ge-QDs appear to not only facilitate the decomposition of proximal Si-containing layers such as SiO 2 , Si 3 N 4 , and Si, but also in turn, mediate the regrowth of SiO 2 [22], densification of Si 3 N 4 [27,28], and the generation of SiGe nanosheets on Si [27,32,39]. Such deconstruction-construction processes dynamically occur as a result of the exquisite interplay between Ge, Si, and O interstitials during the thermal-oxidation process, pointing to ultimately achieving the ability to form self-organized heterostructures of Ge-QD/SiO 2 -shell on Si 3 N 4 and Ge-QD/SiO 2 -shell/SiGe-nanosheet on Si with precise control of the Ge-QD sizes and at the desired spatial locations.…”

“…1). The Ge-QDs were created using the selective oxidation of poly-Si 1 − x Ge x lithographically patterned structures (for instance, pillars and islands) with specifically designed Si 3 N 4 layers on top [22][23][24] or at the sidewalls [25][26][27][28] of Si patterned structures. The proximal Si 3 N 4 layer is one of the key enablers for the formation of Ge spherical QDs and responsible for a unique phenomenon, namely, activating Ge-QD migration in the solid state within the already-formed SiO 2 layers during the thermal-oxidation process.…”

“…EELS mapping, Energy-Dispersive linescans, and spectral analysis (Fig. 4) showed that the densification of Si 3 N 4 is achieved by an increase in both Si and N concentrations with essentially no change in the stoichiometric ratios [35] as well as being accompanied by phase transition from the amorphous to the nanocrystalline state [27,28,35]. The latter phase transition effect was evidenced by the appearance of spotty diffraction rings within nanobeam diffraction (NBD) patterns and diffraction peaks corresponding to α-or β-phase states in X-ray diffraction (XRD) spectra [27,28].…”

“…4) showed that the densification of Si 3 N 4 is achieved by an increase in both Si and N concentrations with essentially no change in the stoichiometric ratios [35] as well as being accompanied by phase transition from the amorphous to the nanocrystalline state [27,28,35]. The latter phase transition effect was evidenced by the appearance of spotty diffraction rings within nanobeam diffraction (NBD) patterns and diffraction peaks corresponding to α-or β-phase states in X-ray diffraction (XRD) spectra [27,28]. Densified Si 3 N 4 is desired for the fabrication of Si 3 N 4 waveguides and related photonic devices due to the significant reduction in H-induced traps and the consequent reductions in absorption/propagation losses.…”

“…The key engineering advantages of our combined, lithographically patterned as well as self-organized Ge-QD/ SiO 2 approaches lie in controllably positioning size-tunable spherical Ge-QDs at desired locations [27,28,39]. In so doing, we have created a large parameter space for designing advanced photonic devices exploiting quantum electrodynamics effects.…”