Photoluminescence in short-period Si/Ge strained-layer superlattices

Zachai, R.; Eberl, K.; Abstreiter, G.; Kasper, E.; Kibbel, H.

doi:10.1103/physrevlett.64.1055

Cited by 200 publications

(43 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…50 It has been shown that in superlattices of an indirect band gap material with a periodicity smaller than the electron mean free path, Brillouin zone folding and band mixing leads to quasi-direct transitions close to the indirect band gap. [51][52][53][54] Considering the present aggregates locally as supercrystals the increased absorption in the red could be understood as such quasi-direct transitions. In addition, the zone folding also modifies the phonon band structure, 55 which additionally may influence the transition probabilities for phonon-assisted indirect transitions.…”

Section: Tunable Optical Properties Of Dispersions and Thin Filmsmentioning

confidence: 99%

Pyrite nanocrystals: shape-controlled synthesis and tunable optical properties via reversible self-assembly

Döblinger

Vaneski

et al. 2011

J. Mater. Chem.

View full text Add to dashboard Cite

Nanocrystals from non-toxic, earth abundant materials have recently received great interest for their potential large-scale application in photovoltaics and photocatalysis. Here, we report for the first time on the shape-controlled and scalable synthesis of phase-pure pyrite (FeS 2 ) nanocrystals employing the simple, inexpensive, thermal reaction of iron-oleylamine complexes with sulfur in oleylamine. Either dendritic nanocrystals (nanodendrites) or nanocubes are obtained by adjusting the iron-oleylamine concentration and thereby controlling the nucleus concentration and kinetics of the nanocrystal growth. Pyrite nanodendrites are reversibly assembled by washing with toluene and redispersed by adding the ligand oleylamine. The assembly-redispersion-process is accompanied by an increased absorption in the red/near-infrared spectral region for the aggregated state. This increased low-energy absorption is due to interactions between the closed-packed nanocrystals. High-concentration nanodendrite dispersions are used to prepare pyrite thin films with strong broadband extinction in the visible and near-infrared. These films are attractive candidates for light harvesting in all inorganic solar cells based on earth abundant, non-toxic materials as well as for photocatalytic applications.

show abstract

Section: Tunable Optical Properties Of Dispersions and Thin Filmsmentioning

confidence: 99%

Pyrite nanocrystals: shape-controlled synthesis and tunable optical properties via reversible self-assembly

Döblinger

Vaneski

et al. 2011

J. Mater. Chem.

View full text Add to dashboard Cite

show abstract

“…For interested readers this has been summarised in many reviews on the subject [14]. Other approaches attempted include the use of silicon-germanium superlattice structures with a periodicity designed to fold the indirect gap in to centre of the Brillouin zone to create a quasi-direct semiconductor system [15]. However, insufficient enhancement of the matrix element for the quasi-direct transition was achieved to make this a viable approach for efficient LEDs.…”

Section: State Of the Art And Future Challenges For Silicon Leds And mentioning

confidence: 99%

Crystalline-silicon-based infra-red LEDs and routes to laser diodes

Lourenço

Homewood

2011

Thin Solid Films

View full text Add to dashboard Cite

“…Electroreflectance measurements of Si4Ge4 superlattices grown on (001)-oriented Si substrates (Pearsall et al, 1987) provided the first experimental evidence of the anticipated modifications to the Si and Ge band structures in such superlattices. It was not until later, when strain-symmetrized SimGen superlattices were first grown on strain-relaxed thick Si1−xGex alloy buffer layers on Si, that indications of the expected enhancement of the PL intensity and a smaller energy gap were obtained (Zachai et al, 1990;Kasper and Schäffler, 1991). Further improvements in the crystal growth conditions led to a positive identification of both of these novel features (Menczigar et al, 1993).…”

Section: Quantum Wellsmentioning

confidence: 99%

Si/SiGe Heterointerfaces in One-, Two-, and Three-Dimensional Nanostructures: Their Impact on SiGe Light Emission

Lockwood

Baribeau

et al. 2016

Front. Mater.

View full text Add to dashboard Cite

Fast optical interconnects together with an associated light emitter that are both compatible with conventional Si-based complementary metal-oxide-semiconductor (CMOS) integrated circuit technology is an unavoidable requirement for the next-generation microprocessors and computers. Self-assembled Si/Si1−xGex nanostructures (NSs), which can emit light at wavelengths within the important optical communication wavelength range of 1.3-1.55 μm, are already compatible with standard CMOS practices. However, the expected long carrier radiative lifetimes observed to date in Si and Si/Si1−xGex NSs have prevented the attainment of efficient light-emitting devices, including the desired lasers. Thus, the engineering of Si/ Si1−xGex heterostructures having a controlled composition and sharp interfaces is crucial for producing the requisite fast and efficient photoluminescence (PL) at energies in the range of 0.8-0.9 eV. In this paper, we assess how the nature of the interfaces between SiGe NSs and Si in heterostructures strongly affects carrier mobility and recombination for physical confinement in three dimensions (corresponding to the case of quantum dots), two dimensions (corresponding to quantum wires), and one dimension (corresponding to quantum wells). The interface sharpness is influenced by many factors, such as growth conditions, strain, and thermal processing, which in practice can make it difficult to attain the ideal structures required. This is certainly the case for NS confinement in one dimension. However, we demonstrate that axial Si/Ge nanowire (NW) heterojunctions (HJs) with a Si/ Ge NW diameter in the range 50-120 nm produce a clear PL signal associated with bandto-band electron-hole recombination at the NW HJ that is attributed to a specific interfacial SiGe alloy composition. For three-dimensional confinement, the experiments outlined here show that two quite different Si1−xGex NSs incorporated into a Si0.6Ge0.4 wavy superlattice structure display PL of high intensity while exhibiting a characteristic decay time that is up to 1000 times shorter than that found in conventional Si/SiGe NSs. The non-exponential PL decay found experimentally in Si/SiGe NSs can be interpreted as resulting from variations in the separation distance between electrons and holes at the Si/SiGe heterointerface. The results demonstrate that a sharp Si/SiGe heterointerface acts to reduce the carrier radiative recombination lifetime and increase the PL quantum efficiency, which makes these SiGe NSs favorable candidates for future light-emitting device applications in CMOS technology.

show abstract

Photoluminescence in short-period Si/Ge strained-layer superlattices

Cited by 200 publications

References 21 publications

Pyrite nanocrystals: shape-controlled synthesis and tunable optical properties via reversible self-assembly

Pyrite nanocrystals: shape-controlled synthesis and tunable optical properties via reversible self-assembly

Crystalline-silicon-based infra-red LEDs and routes to laser diodes

Si/SiGe Heterointerfaces in One-, Two-, and Three-Dimensional Nanostructures: Their Impact on SiGe Light Emission

Contact Info

Product

Resources

About