Abstract
Here, SiGeSn nanostructures were grown via molecular beam epitaxy on a Si (111) substrate with the assistance of Sn droplets. Owing to the thermal effect and the compressive strain induced by a lattice mismatch, Si and Sn atoms were successfully incorporated into the Ge matrix during the Sn-guided Ge deposition process. A low growth temperature of 350 °C produced a variety of SiGeSn nanostructures of different sizes, attributed to the variation of the initial Sn droplet size. Using energy-dispersive X-ray spectroscopy, the Sn, Si and Ge contents of a defect-free SiGeSn nanoisland were approximately determined to be 0.05, 0.09 and 0.86, respectively. Furthermore, as the growth temperature increased past 600 °C, the growth direction of the nanostructure was changed thermally from out-of-plane to in-plane. Meanwhile, the stacked SiGeSn nanowires grown along the 〈112〉 direction remained defect-free, though some threading dislocations were observed in the smooth SiGeSn nanowires along the 〈110〉 direction. These results offer a novel method to grow Si-based SiGeSn nanostructures while possessing important implications for fabricating further optoelectronic devices.
Highlights
Silicon-based photonics has attracted great interest because of its potential to achieve the monolithic integration of photonic devices with state-of-the-art Si electronic circuits, thereby enabling an oncoming Si-based optoelectronic revolution.[1,2,3,4,5,6] While the development of various components for integrated Si photonics is advancing rapidly, there remain many important disadvantages of Si-based photonic devices
Three different SiGeSn nanostructures were obtained with the assistance of Sn droplets, as shown in Fig. 1a: (i) rounded SiGeSn nanobumps; (ii) SiGeSn islands with a at top surface; (iii) SiGeSn islands with a convex top surface
To clarify the formation mechanism of the nanostructures found on sample A, another two reference samples, including sample AS3 (Si deposition on Si (111) with Sn droplets) and sample AS4 (Ge virtual substrate is introduced between the Sn droplet and Si substrate), were grown. No nanostructures such as those on sample A were observed on sample AS3 except for Sn droplets on the surface, as shown in Fig. S3.† The Si deposition produced a thin lm on the Si (111) surface owing to the perfect lattice match
Summary
Silicon-based photonics has attracted great interest because of its potential to achieve the monolithic integration of photonic devices with state-of-the-art Si electronic circuits, thereby enabling an oncoming Si-based optoelectronic revolution.[1,2,3,4,5,6] While the development of various components for integrated Si photonics is advancing rapidly, there remain many important disadvantages of Si-based photonic devices.
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