Transmission electron microscopy is used to study the morphology and the composition profile of “pure” Ge islands grown at high temperature on Si(001) by molecular beam epitaxy. An alloying process, involving mass transport from the substrate to the islands during the island growth, was identified. It was found that, as a result of Si mass transport to the Ge islands, the island/substrate interface moves towards the substrate, and trenches form on the substrate surface around the islands. Reduction of the misfit strain at the island/substrate interface is the driving force for this process.

A silicon light emitter in telecom-band based on a single germanium quantum dot precisely embedded in a silicon photonic crystal nanocavity is fabricated by a scalable method. A sharp resonant luminescence peak is observed at 1498.8 nm, which is enhanced by more than three orders of magnitude. The Purcell factor for the fundamental resonant mode is estimated from enhancement factor and increased collection efficiency. The cavity modes coupled to the ground state and excited state emission of germanium quantum dot are identified in the luminescence spectrum. Our devices provide a CMOS-compatible way of developing silicon-based low-power consuming light emitters, and are promising for realizing on-chip single photon sources.

Strong infrared photoluminescence (PL) was observed for the first time from black Si (b-Si) formed by femtosecond laser irradiation and treated by rapid thermal annealing. The PL peak energy changes from 0.78 to 0.84 eV (1.59 to 1.48 μm) when increasing the annealing temperature from 500°C to 1200°C, showing a tunable property. Compared to those after annealing at 1000°C, both the peak intensity and the peak energy change slightly after annealing at higher temperatures of 1100°C and 1200°C, showing a high thermal stability of their structures and PL properties. With the $x$-ray photoelectron spectroscopy (XPS) results from the b-Si before and after etching in KOH solution, the PL is attributed to dislocation-related (D1) luminescence rather than sulfur-related impurity center luminescence. The integrated intensity of D1 PL as a function of excitation power can be fitted by $I\propto P^m$ with $m$ of 0.58, suggesting that the PL of the b-Si sample originates from the recombination of bound-to-bound states. The high thermal activation energy of 75.2 meV suggests a high quenching temperature of D1 PL, showing a potential of application at room temperature. This work may promote the progress of research on b-Si in the area of Si-based optoelectronics.

Very small and compactly arranged GeSi nanowires could self-assembled on vicinal Si (001) substrates with ~8° off toward ⟨110⟩ during Ge deposition. The nanowires were all oriented along the miscut direction. The small ration of height over width of the nanowire indicated that the nanowires were bordered partly with {1 0 5} facets. These self-assembled small nanowires were remarkably influenced by the growth conditions and the miscut angle of substrates in comparison with large dome-like islands obtained after sufficient Ge deposition. These results proposed that the formation of the nanowire was energetically driven under growth kinetic assistance. Three-dimensionally self-assembled GeSi nanowires were first realized via multilayer Ge growth separated with Si spacers. These GeSi nanowires were readily embedded in Si matrix and compatible with the sophisticated Si technology, which suggested a feasible strategy to fabricate nanowires for fundamental studies and a wide variety of applications.PACS: 81.07.Gf, 81.16.Dn, 68.65.-k, 68.37.Ps