共查询到20条相似文献,搜索用时 31 毫秒
1.
Zhongying Xue Xing WeiBo Zhang Aimin WuMiao Zhang Xi Wang 《Applied Surface Science》2011,257(11):5021-5024
A fully relaxed Si0.75Ge0.25 film with low dislocation densities is fabricated by epitaxial growth on SOI substrate without depositing graded buffers. The relaxation mechanism of the SiGe layer directly grown on SOI substrate is also analyzed. For SiGe grown on SOI with low Ge content, the strain is redistributed between SiGe and the top Si of SOI substrate, and the strain residing in SiGe layer can be fully relaxed by the formation and expansion of dislocation half-loops near the SiGe/Si interface. The surface morphology and crystal quality of all samples are analyzed by optical microscopy and transmission electron microscopy (TEM), respectively. Compared to the Si0.75Ge0.25 layer epitaxially grown on graded buffer, the Si0.75Ge0.25 directly grown on SOI substrate appears good surface morphology and perfect crystal quality. 相似文献
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R. Turan B. Aslan O. Nur M.Y.A. Yousif M. Willander 《Applied Physics A: Materials Science & Processing》2001,72(5):587-593
We have studied the effect of the strain relaxation on the band-edge alignments in a Pt/p-Si1-xGex Schottky junction with x=0.14 by internal photoemission spectroscopy and current–voltage measurements. We have shown that
the variations in the band-edge alignments can be observed directly by measuring the optical and electrical properties of
a simple Schottky junction. The strain in the Si1-xGex layer has been partially relaxed by thermal treatments at two different temperatures. The degree of relaxation and other
structural changes have been determined by a high-resolution X-ray diffractometer. Both optical and electrical techniques
have shown that the barrier height of the Pt/Si0.86Ge0.14 junction increases with the amount of relaxation in the Si1-xGex layer. This shows that the valence-band edge of the Si1-xGex layer moves away from the Fermi level of the Pt/Si1-xGex junction. The band-edge movement results from the increase in the band gap of the Si1-xGex layer after the strain relaxation. This result agrees with the theoretical predictions for the strain-induced effects on
the Si1-xGex band structure.
Received: 18 October 2000 / Accepted: 19 December 2000 / Published online: 23 March 2001 相似文献
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M.F. Fyhn J. Lundsgaard Hansen J. Chevallier A. Nylandsted Larsen 《Applied Physics A: Materials Science & Processing》1999,68(2):259-262
1-x Snx (0.01≤x≤0.04) layers on Si(001) and relaxed Si-Ge substrates. The Si1-xSnx layers were investigated using Rutherford backscattering spectrometry, atomic force microscopy, transmission electron microscopy
and preferential-etching experiments. The investigation of surfactant-mediated growth of epitaxial Si1-xSnx was motivated by a possible use of relatively higher growth temperatures without relaxation by surface precipitation. It
is demonstrated that higher growth temperatures are attainable when Bi is used as surfactant if the surface-segregated Sn
layer is relatively small, equivalent to Si1-xSnx layers of low strain. The increase in growth temperature leads to a significant improvement in the crystalline quality of
these Si1-xSnx layers.
Received: 4 December 1998/Accepted: 9 December 1998 相似文献
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x Si1-x/Si heterostructures have been obtained. Here the chemical effects seem to be of less importance. The Fermi-level effect determines
the ionized boron solubilities in GexSi1-x and in Si, as well as the thermal equilibrium concentration of the singly-positively-charged crystal self-interstitials I+ which governs the boron diffusion process. The junction carrier concentration affects the concentration of I+ and solubility of B in the region and hence controls B diffusion across the heterojunction.
Received: 20 August 1998/Accepted: 23 September 1998 相似文献
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The electronic structure of silicon carbide with increasing germanium content have been examined using first principles calculations based on density functional theory. The structural stability is analysed between two different phases, namely, cubic zinc blende and hexagonal phases. The zinc blende structure is found to be the stable one for all the Si1-xGexC semiconducting carbides at normal pressure. Effect of substitution of Ge for Si in SiC on electronic and mechanical properties is studied. It is observed that cubic SiC is a semiconductor with the band gap value 1.243?eV. The band gap value of SiC is increased due to the substitution of Ge and the band gap values of Si 0.75 Ge 0.25 C, Si 0.50 Ge 0.50 C, Si 0.25 Ge 0.75 C and GeC are 1.322 eV, 1.413 eV, 1.574 eV and 1.657?eV respectively. As the pressure is increased, it is found that the energy gap gets decreased for Si1-x GexC (X?=?0, 0.25, 0.50, 0.75, 1). The elastic constants satisfy the Born – Huang elastic stability criteria. The bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio are also calculated and compared with the other available results. 相似文献
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This work deals with the optoelectronic properties of heterostructures built
on type II Si1-xGex/Si strained quantum wells grown on relaxed
Si1-yGey/Si (001) pseudo-substrates. To limit the intrinsic
problem due to the real-space indirect nature of the interface, we propose
and model three heterostructures having three different potential profiles
of the valence and conduction bands which consist in various arrangements of
Si and Si1-xGex barriers of different Ge contents. The proposed
stacks are designed in a pragmatic way for a pseudomorphic growth on relaxed
Si1-yGey assuming individual layer thickness being smaller than
the known critical thickness and an overall compensation of the strain.
Variation of thickness and compositions (x>y) permits to optimize i) the
quantum confinement of electrons and heavy-hole levels and ii) the wave
function's overlap and the out-of-plane oscillator strength. The optimum
parameters satisfy a fundamental emission at a key 1.55 μm wavelength
below the absorption edge of each layer constitutive of the stacks. A
comparison between the characteristics of the three heterostructures brings
out the superior advantages of the W architecture. 相似文献
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《Superlattices and Microstructures》1988,4(3):391-394
The development of Si and Si1−xGex layer growth by molecular beam epitaxy has enabled heterostructures and HEMT devices to be made with Group IV semiconductors. Strain is very important in determining the electronic behaviour of this system and as an initial step towards understanding mobility in SiGe HEMT structures a Monte Carlo technique has been used to simulate electron transport in bulk Si, strained by commensurate growth on a (001) Si1−yGey buffer. The in-plane mobility initially increases with increasing strain but then falls at higher strains and fields. Results are presented for both undoped and 1017 cm−3 n-type Si, fields of 102 to 104 Vcm−1 and strain levels up to the equivalence of growth on a Si0.25Ge0.75 buffer. The results are explained by the splitting of the degenerate conduction band minimum and the transition probability between the two-fold and four-fold split minima. 相似文献
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在Si(100)衬底上用分子束外延在不同的温度下生长了不同组份的GexSi1-x/Si应变层超晶格。用反射式高能电子衍射、X射线双晶衍射、卢瑟福背散射、透射电子显微镜以及Raman。散射等测试方法研究了GexSi1-x/Si超晶格的生长及其结构特性。结果表明,对不同合金组份的超晶格,其最佳生长温度不同。x值小,生长温度高;反之,则要求生长温度低。对于x为0.1—0.6,在400—600℃的生长温度范围能够长成界面平整、
关键词: 相似文献
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E. Kasper H. J. Herzog H. Kibbel 《Applied Physics A: Materials Science & Processing》1975,8(3):199-205
One-dimensional SiGe superlattices with periods ranging from 100 to 800 Å have been deposited on Si substrates by periodically varying the Ge content of a mixed Si1-x Ge x multilayer structure fromx=0 tox=0.15. The deposition was successful, employing and UHV evaporation technique at a substrate temperature of 750°C fulfilling the four conditions: Single crystal growth, no interdiffusion, two-dimensional growth, and pseudomorphic growth. It is shown that mismatch above 8 · 10?3 favours growth by three-dimensional nucleation. The experimentally determined spacing of misfit dislocations is compared with theoretical results obtained by van der Merwe. The pseudomorphic growth behaviour of layers thinner than a critical thickness could be confirmed. 相似文献
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High mobility metal-oxide-semiconductor-field-effect-transistors (MOSFETs) are demonstrated on high quality epitaxial Si0.75Ge0.25 films selectively grown on Si (100) substrates. With a Si cap processed on Si0.75Ge0.25 channels, HfSiO2 high-k gate dielectrics exhibited low C–V hysteresis (<10 mV), interface trap density (7.5 × 1010), and gate leakage current (∼10−2A/cm2 at an EOT of 13.4 Å), which are comparable to gate stack on Si channels. The mobility enhancement afforded intrinsically by the Si0.75Ge0.25 channel (60%) is further increased by a Si cap (40%) process, resulting in a combined ∼100% enhancement over Si channels. The Si cap process also mitigates the low potential barrier issues of Si0.75Ge0.25 channels, which are major causes of the high off-state current of small band gap energy Si0.75Ge0.25 pMOSFETs, by improving gate control over the channel. 相似文献
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High-quality relaxed SiGe films on Si (0 0 1) have been demonstrated with a buffer layer containing modified SiGe (m-SiGe) islands in ultra-high vacuum chemical vapor deposition (UHV/CVD) system. The m-SiGe islands are smoothened by capping an appropriate amount of Si and the subsequent annealing for 10 min. This process leads to the formation of a smooth buffer layer with non-uniform Ge content. With the m-SiGe-dot multilayer as a buffer layer, the 500-nm-thick uniform Si0.8Ge0.2 layers were then grown. These m-SiGe islands can serve as effective nucleation centers for misfit dislocations to relax the SiGe overlayer. Surface roughness, strain relaxation, and crystalline quality of the relaxed SiGe overlayer were found to be a function of period's number of the m-SiGe-dot multilayer. By optimizing period number in the buffer, the relaxed Si0.8Ge0.2 film on the 10-period m-SiGe-dot multilayer was demonstrated to have a threading dislocation density of 2.0 × 105 cm−2 and a strain relaxation of 89%. 相似文献
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C. O'Raifeartaigh A. Nylandsted Larsen F. Cristiano P. L. F. Hemment 《Applied Physics A: Materials Science & Processing》1995,61(6):579-585
Supersaturated solid solutions of substitutional, electrically active Sb have been obtained by ion implantation of relaxed epitaxial Si1?xGex alloy layers grown on compositionally graded buffers. Substitutional and nonsubstitutional Sb fractions in relaxed Si0.85Ge0.15, Si0.65Ge0.35 and Si0.50Ge0.50 alloy layers implanted to a dose of 5×1015 Sb cm?2 and annealed isothermally at temperatures ranging from 400 to 850°C have been studied by Rutherford backscattering/channeling, transmission electron microscopy and Hall-effect and sheet resistivity measurements. A supersaturated solution of Sb corresponding to a peak carrier concentration of 4×1020 cm?3 and an electrically active fraction of 40% of the implanted dose is observed by Hall measurements for the case of Si0.85Ge0.15 and Si0.65Ge0.35 alloys annealed at 550°C. 相似文献
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Yu. B. Bolkhovityanov A. K. Gutakovskii A. S. Deryabin L. V. Sokolov 《Physics of the Solid State》2014,56(2):247-253
Heterostructures Ge/Ge x Si1 ? x /Si(001) grown by molecular beam epitaxy have been investigated using atomic scale high-resolution electron microscopy. A germanium film (with a thickness of 0.5–1.0 μm) grown at a temperature of 500°C is completely relaxed. An intermediate Ge0.5Si0.5 layer remains in a strained metastable state, even though its thickness is 2–4 times larger than the critical value for the introduction of 60° misfit dislocations. It is assumed that the Ge/GeSi interface is a barrier for the penetration of dislocations from a relaxed Ge layer into the GeSi layer. This barrier is overcome during annealing of the heterostructures for 30 min at a temperature of 700°C, after which dislocation networks having different degrees of ordering and consisting predominantly of edge misfit dislocations are observed in the Ge/GeSi and GeSi/Si(001) heteroboundaries. 相似文献
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Five-layered Si/SixGe1−x films on Si(1 0 0) substrate with single-layer thickness of 30 nm, 10 nm and 5 nm, respectively were prepared by RF helicon magnetron sputtering with dual targets of Si and Ge to investigate the feasibility of an industrial fabrication method on multi-stacked superlattice structure for thin-film thermoelectric applications. The fine periodic structure is confirmed in the samples except for the case of 5 nm in single-layer thickness. Fine crystalline SixGe1−x layer is obtained from 700 °C in substrate temperature, while higher than 700 °C is required for Si good layer. The composition ratio (x) in SixGe1−x is varied depending on the applied power to Si and Ge targets. Typical power ratio to obtain x = 0.83 was 7:3, Hall coefficient, p-type carrier concentration, sheet carrier concentration and mobility measured for the sample composed of five layers of Si (10 nm)/Si0.82Ge0.18 (10 nm) are 2.55 × 106 /°C, 2.56 × 1012 cm−3, 1.28 × 107 cm−2, and 15.8 cm−2/(V s), respectively. 相似文献
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《Superlattices and Microstructures》1994,16(1):105-108
Results are presented concerning the characterization of p-Si/Si1-xGex/Si quantum wells (QW) by space charge spectroscopy. Analysis of potential barriers at the QW enables us to determine the valence band offset from such measurements. Admittance spectroscopy data of QWs with 30 nm undoped spacers, acceptor concentration NA of about 1017cm-3 in the cap and buffer layers, x=0.25 and a QW thickness in the range from 1 to 5 nm are in fair agreement with the proposed theoretical model. A decrease of the effective potential barriers due to hole tunneling via shallow acceptor states in the barrier is experimentally confirmed for 5 nm QW structures without spacers. 相似文献