Excitation-dependent photoluminescence in Ge∕Si Stranski-Krastanov nanostructures

Kamenev, B. V.; Lee, Eun Kyu; Chang, H.-Y.; Han, Hui; Grebel, Haim; Tsybeskov, L.; Kamins, Theodore I.

doi:10.1063/1.2361198

Cited by 26 publications

(27 citation statements)

References 27 publications

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“…The PL efficiencies in MBE and CVD grown samples are comparable (≥1% at low excitation intensity). The same sub-linear (close to square root) dependence on excitation intensity (on a log-log plot) for PL associated with Ge-rich SiGe clusters has been found in nearly all 3D Si/SiGe NSs grown by both CVD and MBE [13]. The PL spectra in 3D Si/SiGe NSs, which is similar to that in III-V quantum wells with type II energy band alignment, exhibit a blue shift as the excitation intensity increases.…”

Section: Invited Articlesupporting

confidence: 67%

“…We suggest that in 3D Si/SiGe multilayer NSs with thin Si layers at low excitation intensity, the electron-hole separation and non-radiative carrier recombination are mainly controlled by hole tunneling between SiGe clusters. Due to significant variations in SiGe cluster size, shape and chemical composition, the process of hole tunneling could be assisted by phonon emission and/or absorption [13]. Therefore, the observed PL thermal quenching activation energy is close to the Si TO phonon energy.…”

Section: Invited Articlementioning

confidence: 82%

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Self‐assembled silicon‐germanium nanostructures for CMOS compatible light emitters

Lockwood

Tsybeskov

2011

Phys. Status Solidi C

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To be commercially valuable, light emitters based on SiGe nanostructures should be efficient, fast, operational at room temperature, and be compatible with the CMOS technology. Also, the emission wavelength should match the optical waveguide low‐loss spectral region of 1.3–1.6 μm. Among other approaches, epitaxially‐grown Si/SiGe quantum dot/quantum well complexes produce efficient photoluminescence and electroluminescence in the required spectral range. Until recently, the major roadblocks for practical applications of these devices were strong thermal quenching of the luminescence quantum efficiency and a long carrier radiative lifetime. The latest progress in the understanding of physics of carrier recombination in Si/SiGe nanostructures is reviewed, and a new route toward CMOS compatible light emitters for on‐chip optical interconnects is proposed. © Her Majesty the Queen in Right of Canada [2011]. Reproduced with the permission of the Minister of Industry

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Section: Invited Articlesupporting

confidence: 67%

Section: Invited Articlementioning

confidence: 82%

Self‐assembled silicon‐germanium nanostructures for CMOS compatible light emitters

Lockwood

Tsybeskov

2011

Phys. Status Solidi C

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“…In type II band alignment, the electrons and holes are spatially separated, with in this case the electrons localized in Si and the holes located in the SiGe NS, which explains the experimentally observed long lifetime of the photoluminescence (PL) in Si/SiGe NSs (Kamenev et al, 2005(Kamenev et al, , 2006Tsybeskov and Lockwood, 2009;Mala et al, 2013). The SiGe NS PL saturates quickly, as the slow radiative recombination cannot compete with the faster Auger recombination even for modest carrier concentrations (Kamenev et al, 2005(Kamenev et al, , 2006Tsybeskov and Lockwood, 2009;Mala et al, 2013). For these reasons, it is necessary to produce Si/Si1−xGex heterostructures with good control over their composition and interface abruptness to enable the production of the sought after fast and efficient PL at 0.8-0.9 eV.…”

mentioning

confidence: 97%

“…However, the long carrier radiative lifetimes observed in such Si/Si1−xGex NSs hinder the development of efficient light-emitting devices and, thereby, the construction of lasers (Sturm et al, 1991;Zheng et al, 1994;Lu et al, 1995;Lockwood, 1998;Pavesi et al, 2000;Tsybeskov and Lockwood, 2009). The usual model for radiative recombination in Si/Si1−xGex NSs is based on a type II heterointerface energy band alignment (see Figure 1) (Kamenev et al, 2006;Mala et al, 2013). In type II band alignment, the electrons and holes are spatially separated, with in this case the electrons localized in Si and the holes located in the SiGe NS, which explains the experimentally observed long lifetime of the photoluminescence (PL) in Si/SiGe NSs (Kamenev et al, 2005(Kamenev et al, , 2006Tsybeskov and Lockwood, 2009;Mala et al, 2013).…”

mentioning

confidence: 99%

“…The usual model for radiative recombination in Si/Si1−xGex NSs is based on a type II heterointerface energy band alignment (see Figure 1) (Kamenev et al, 2006;Mala et al, 2013). In type II band alignment, the electrons and holes are spatially separated, with in this case the electrons localized in Si and the holes located in the SiGe NS, which explains the experimentally observed long lifetime of the photoluminescence (PL) in Si/SiGe NSs (Kamenev et al, 2005(Kamenev et al, , 2006Tsybeskov and Lockwood, 2009;Mala et al, 2013). The SiGe NS PL saturates quickly, as the slow radiative recombination cannot compete with the faster Auger recombination even for modest carrier concentrations (Kamenev et al, 2005(Kamenev et al, , 2006Tsybeskov and Lockwood, 2009;Mala et al, 2013).…”

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confidence: 99%

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

Lockwood

Baribeau

et al. 2016

Front. Mater.

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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.

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Three-Dimensional Silicon–Germanium Nanostructures for CMOS-Compatible Light Emitters

Lockwood

Tsybeskov

2010

Nanotechnology for Electronics, Photonics, and Renewable Energy

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Excitation-dependent photoluminescence in Ge∕Si Stranski-Krastanov nanostructures

Cited by 26 publications

References 27 publications

Self‐assembled silicon‐germanium nanostructures for CMOS compatible light emitters

Self‐assembled silicon‐germanium nanostructures for CMOS compatible light emitters

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

Three-Dimensional Silicon–Germanium Nanostructures for CMOS-Compatible Light Emitters

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