Raman spectra of intrinsic and doped hydrogenated nanocrystalline silicon films

Wei, Wensheng; Xu, Guo‐Bo; Wang, Jinliang; Wang, Tianmin

doi:10.1016/j.vacuum.2006.09.006

Cited by 90 publications

(53 citation statements)

References 23 publications

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“…This effect has also been experimentally observed in nanocrystalline 14 and polycrystalline 15 Si films. The following expression was developed in the case of n-type bulk Si: 13…”

Section: Applied Physics Letters 92 233506 ͑2008͒supporting

confidence: 67%

Constraints on micro-Raman strain metrology for highly doped strained Si materials

O'Reilly

Horan

McNally

et al. 2008

Applied Physics Letters

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Ultraviolet ͑UV͒, low penetration depth, micro-Raman spectroscopy, and high-resolution x-ray diffraction ͑HRXRD͒ are utilized as complementary, independent stress characterization tools for a range of strained Si samples doped by low energy ͑2 keV͒ Sb ion implantation. Following dopant implantation, good agreement is found between the magnitudes of strain measured by the two techniques. However, following dopant activation by annealing, strain relaxation is detected by HRXRD but not by micro-Raman. This discrepancy mainly arises from an anomalous redshift in the Si Raman peak position originating from the high levels of doping achieved in the samples. This has serious implications for the use of micro-Raman spectroscopy for strain characterization of highly doped strained Si complementary metal-oxide semiconductor devices and structures therein. We find a direct correlation between the Si Raman shift and peak carrier concentration measured by the differential Hall technique, which indicates that UV micro-Raman may become a useful tool for nondestructive dopant characterization for ultrashallow junctions in these Si-based materials. The enhancement of carrier mobilities through the introduction of strain in the channel region of metal-oxide semiconductor field effect transistors is an important option in order to maintain historical complementary metal-oxide semiconductor ͑CMOS͒ performance trends. 1 The production of ultrashallow junctions for the source/drain extension region using low energy ion implantation will be required for future CMOS devices. Biaxial tensile strain reduces the sheet resistance ͑R S ͒ of highly doped n type layers created by As or Sb implantation. The effect can be stronger for Sb, when R s lowering results not only from strain enhanced mobility, but also from an improvement in Sb metastable solubility in the presence of strain. 2 This makes Sb an interesting alternative to As for ultrashallow junctions in strain-engineered CMOS devices. Since an early study by Anastassakis et al., 3 Raman scattering has been widely used as a strain characterization technique in the semiconductor industry 4-6 and is often utilized for strain metrology in strained Si films. 7,8 Our results show that there are practical difficulties associated with the use of micro-Raman as a strain characterization technique for highly doped ultrashallow junction Si CMOS device structures.Experiments were performed on two types of tensilestrained Si wafers each grown on Si 1−x Ge x relaxed buffer layers with x = 0.2 and x = 0.17, and strained Si thicknesses of 43 and 17.5 nm, respectively. Each wafer was implanted with a 2 keV Sb ion dose of between 1 ϫ 10 14 and 1 ϫ 10 15 cm −2 creating a junction at a depth of around 10 nm.Nominally unstrained control samples were prepared using conventional p-type Si wafers for comparison. The implanted dose was confirmed by medium-energy ion scattering ͑MEIS͒. Dopant activation was achieved by rapid thermal annealing ͑RTA͒ wafer pieces for 10 s in N 2 in the range of 600-800°C. Room ...

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“…This effect has also been experimentally observed in nanocrystalline 14 and polycrystalline 15 Si films. The following expression was developed in the case of n-type bulk Si: 13…”

Section: Applied Physics Letters 92 233506 ͑2008͒supporting

confidence: 67%

Constraints on micro-Raman strain metrology for highly doped strained Si materials

O'Reilly

Horan

McNally

et al. 2008

Applied Physics Letters

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“…The proportion of the crystalline-to-amorphousphase in c-Si is about 96%, as calculated from the relative intensity of the two peaks. [25][26][27] The average grain size of the c-Si, estimated from the peak shift of the TO phonon mode from that of single crystalline Si, is about 10 nm, suggesting that the c-Si thin film is well crystallized after SPC. Under the same SPC conditions, i-cSi-o shows both the amorphous and crystalline Si peaks at 478 cm À1 and at 512 cm À1 (Fig.…”

mentioning

confidence: 99%

Tailoring the Electrical Properties of Inverse Silicon Opals ‐ A Step Towards Optically Amplified Silicon Solar Cells

et al. 2009

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It has been just over two decades since John and Yablonovitch theoretically predicted the existence of a complete photonic band gap in 3D silicon photonic crystals, a range of wavelengths for which light is forbidden to propagate in all three spatial dimensions.[1] This breakthrough inspired global research activity to transform the idea into practice, at the time driven mainly by the field of optical telecommunications.[2] Since then, several studies have demonstrated the potential advantages of photonic crystals for other applications, such as light emitting diodes, [3] lasers, [4,5] wave guides, [6,7] photocatalysts, [8] displays, [9,10] and solar cells. [11][12][13] In particular, the inverse silicon opal (i-Si-o) with a high refractive-index contrast has attracted attention because of its demonstrated complete photonic band gap at 1.5 mm and the possibility of large-scale synthesis.[14] While the optical properties of i-Si-o have been thoroughly investigated, [15,16] little research has been focused on its electrical behaviour, knowledge that would underpin the development of any kind of electro-optical device based on i-Si-o. It can be envisioned that the electrical properties of i-Si-o with its 3D open-framework microstructure could be very different from that of Si thin films, similar to the different behaviour observed for electrochemically etched porous silicon.[17] It is therefore our opinion that the electrical properties of i-Si-o need to be elucidated, as this data will be critical for applications such as optically amplified silicon solar cells. [18] The purpose of the work described herein is to understand the electrical properties of i-Si-o, focusing in particular on the influence of the photonic-crystal lattice constant and the effect of crystallinity and hydrogen-plasma passivation of Si on the electrical conductivity of i-Si-o, and how these material properties correlate with the optical properties of i-Si-o.To reach our objectives, we fabricated i-Si-o by infiltrating the voids of a silica-opal template with Si using chemical vapor deposition (CVD), and subsequently etching the silica spheres with hydrofluoric acid (HF).[19] Accurate measurements of the dc electrical dark conductivities (s d ) require electrodes and electrical contacts on the i-Si-o films. Therefore, instead of using glass substrates, which are most commonly employed, we prepared all samples on sapphire substrates due to their high stability against HF etching. Note that the i-Si-o fabricated on glass substrates usually gets detached and becomes free-standing after HF etching, while high-quality intact i-Si-o films can be achieved on sapphire substrates.The as-deposited Si obtained by CVD in the interstitial voids of silica opals is amorphous. We denote them inverse amorphoussilicon opals (i-aSi-os). In order to integrate i-aSi-o in optical, electro-optical, or electrical devices, it is important to achieve inverse crystalline-silicon opals (i-cSi-o), because crystalline silicon has a much higher conductivity than amorphous s...

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“…Meanwhile, the C TO decreases with decreasing hydrogen content in thin films [10]. The TA mode intensity at about 150 cm -1 is considered to be proportional to the density of dihedral angle fluctuations, reflecting the medium-range order (MRO) of amorphous network [12]. The existence of coordination defects is necessary for the presence of the LA band at 300 cm -1 and the LO band at 410 cm -1 [13].…”

Section: Amorphous Networkmentioning

confidence: 99%

Structure and electronic states in a-Si:H thin films

et al. 2012

J Mater Sci

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The hydrogenated amorphous silicon (a-Si:H) thin films were prepared by plasma enhanced chemical vapor deposition at various substrate temperatures. This paper examined the relationship between structural evolution and electronic states of the tested thin films. Raman spectroscopy was used to evaluate the structural evolution in amorphous network. Meanwhile, Fourier transform infrared spectroscopy was applied to explore the change of hydrogen in thin films. Results show that the order of network on short and intermediate scales, the content and bonding mode of bonded hydrogen, as well as the intrinsic stress and silicon coordination defects, and closed rings in the thin films, vary with the deposition temperature. The dielectric spectra of samples were measured using SE850 spectra ellipsometer. The density of electronic band states (DOS) in both valence band and conduction band for a-Si:H thin films was obtained by fitting the measured dielectric spectra. The results, verified by optical measurement, reveal that the effect of hydrogenation on band edge DOS is predominant in comparison with that of network relaxation.

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Raman spectra of intrinsic and doped hydrogenated nanocrystalline silicon films

Cited by 90 publications

References 23 publications

Constraints on micro-Raman strain metrology for highly doped strained Si materials

Constraints on micro-Raman strain metrology for highly doped strained Si materials

Tailoring the Electrical Properties of Inverse Silicon Opals ‐ A Step Towards Optically Amplified Silicon Solar Cells

Structure and electronic states in a-Si:H thin films

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