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1.
Based on the analysis of vertical electric potential distribution across the dual-channel strained p-type Si/strained Si 1-x Ge x /relaxd Si 1-y Ge y (s-Si/s-SiGe/Si 1-y Ge y) metal-oxide-semiconductor field-effect transistor (PMOSFET),an-alytical expressions of the threshold voltages for buried channel and surface channel are presented.And the maximum allowed thickness of s-Si is given,which can ensure that the strong inversion appears earlier in the buried channel (compressive strained SiGe) than in the surface channel (tensile strained Si),because the hole mobility in the buried channel is higher than that in the surface channel.Thus they offer a good accuracy as compared with the results of device simulator ISE.With this model,the variations of threshold voltage and maximum allowed thickness of s-Si with design parameters can be predicted,such as Ge fraction,layer thickness,and doping concentration.This model can serve as a useful tool for p-channel s-Si/s-SiGe/Si 1-y Ge y metal-oxide-semiconductor field-effect transistor (MOSFET) designs. 相似文献
2.
《Superlattices and Microstructures》1988,4(2):173-180
In this paper, the results of Hg1−xZnxTeCdTe strained layer superlattices grown by MBE are reported, and compared to Hg1−xCdxTeCdTe superlattices. Both Type III and Type I Hg1−xZnxTeCdTe superlattices with different strain have been grown on CdTe(111)B/GaAs(100) and CdTe(100)/GaAs(100) substrates and characterized by electron, X-ray diffraction, infrared transmission and Hall measurements. The values of hole mobility between 5×103 up to 2×104cm2v−1s−1 at T = 23K along (111)B growth orientation and up to 4.9×104cm2v−1s−1 at T = 5K along (100) growth orientation are obtained for Type III superlattices whereas in Type I superlattices, the hole mobility is between 200–300cm2v−1s−1. This drastic change in the hole mobility between Type III and Type I superlattices along with the role of the strain are discussed in this paper. 相似文献
3.
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
4.
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
5.
《Solid State Ionics》1988,26(4):279-286
In the solid solutions of Na3+3x−yY1−xSi3−yPyO9, new fast Na+ -conductors were obtained. The ionic conductivity, σ, and the activation energy, E, of the most conductive material, Na4.425Y0.375Si2.55P0.45O9 were 5 × 10−3 S/cm at 300°C and 10 kcal/mol, respectively. Those values were strongly dependent upon the composition. With an increase of Na concentration, [Na], σ increased and E decreased. Accommodation of higher [Na] in the structure was madefeasible by decreasing [Y] and increasing [P]. Based on the crystal structure assumed for Na3+3x−yY1−xSi3−yPyO9 and on the above results, a conduction model was presented. The structural consideration revealed that a conduction path is formed along the 〈1 1 1 〉 direction, where Y3+ ions locate in the way of Na+ ions. 相似文献
6.
N. V. Vostokov Yu. N. Drozdov Z. F. Krasil’nik O. A. Kuznetsov A. V. Novikov V. A. Perevoshchikov M. V. Shaleev 《Physics of the Solid State》2005,47(1):42-45
Relaxed step-graded buffer layers of Si1?xGex/Si(001) heterostructures with a low density of threading dislocations are grown through chemical vapor deposition at atmospheric pressure. The surface of the Si1?xGex/Si(001) (x ~ 25%) buffer layers is subjected to chemical mechanical polishing. As a result, the surface roughness of the layers is decreased to values comparable to the surface roughness of the Si(001) initial substrates. It is demonstrated that Si1?xGex/Si(001) buffer layers with a low density of threading dislocations and a small surface roughness can be used as artificial substrates for growing SiGe/Si heterostructures of different types through molecular-beam epitaxy. 相似文献
7.
8.
We present the formation of single-phase Si1−xGex (x=0.2, 0.4, 0.6, and 0.8) alloy nanocrystals dispersed in a SiO2 matrix. The studied samples were prepared by co-sputtering with excess Si1−xGex in SiO2 of approximately 33 at%. Upon heat treatment, crystallization of Si1−xGex alloys was examined by using X-ray diffraction and high-resolution transmission electron microscopy measurements. Single structure of face-centered cubic nanocrystals in a space group Fd-3m was concluded. The average nanocrystal size (from 2 nm to 10 nm) and the lattice constant a of the single-phase Si1−xGex nanocrystals were found to increase with the Ge composition parameter x. Density functional theory-generalized gradient approximation calculation showed the replacement of Ge into the Si sites and vice versa. 相似文献
9.
《Superlattices and Microstructures》1994,16(2):121
The local atomic structure and lattice dynamics are studied for strain compensated Si1-x-yGexCy layers grown by molecular beam epitaxy on Si (001) substrates. The layers were characterized by transmission electron microscopy, x-ray diffraction, and Raman scattering and modeled using a valence-force field model. For a [Ge]/[C] ratio of approximately ten, the lattice constant in the growth direction is equal to that of the substrate, indicating an absence of macroscopic strain. Experimental and theoretical results are compatible with Vegard's rule. To handle the large bond length distortions near C atoms properly, the valence-force field model used includes anharmonic effects via bond-length-dependent interatomic force constants which were determined from ab initio density-functional calculations. The dependence of the Raman spectra on strain and composition of Si1-x-yGexCy layers can be explained by the model calculations. 相似文献
10.
《Superlattices and Microstructures》1999,25(1-2):301-306
To fabricate high quality SiGe/Si heterostructures, control of intermixing between Si and Ge is essential during crystal growth. This paper describes the recent progress of ‘intermixing-controlled epitaxy’. A combined method of MBE (molecular beam epitaxy) and SPE (solid-phase epitaxy) was developed and used to fabricate a new heterostructure (n-Si0.8Ge0.2/Si channel/Si1 − xGexbuffer layer/Si substrate). Observation by TEM demonstrated that the hetero-interface obtained by SPE was atomically flat. This interface provides the ultrahigh mobility of a two-dimensional electron gas (2DEG). In addition, the influence of atomic-hydrogen irradiation during MBE on Ge dispersion in the SiGe mixed crystal is examined. Results indicate that the number of Ge–Ge pairings was decreased by hydrogen irradiation. Such a decrease deformed the local symmetry of the Si–Ge bond from tetrahedral symmetry. As a result, photoluminescence intensity was sucessfully increased. 相似文献
11.
《Surface science》1989,223(3):L920-L926
We simulate the epitaxial growth and annealing of GexSi1−x alloys on a Si(001) substrate using a stochastic Monte Carlo technique. Initiation of phase segregation into Si(001) and Ge(001) layers is obtained in our simulation. This results from the kinetically more active nature of Ge atoms as compared to Si atoms, together with an effect arising from the compressive strain in the alloy layers. We discuss our results in the light of the existing experimental data. 相似文献
12.
《Solid State Communications》1986,57(4):235-236
The stoichiometric thin films of SiO have been studied by Raman scattering. The spectra indicate three main peaks at 444 cm−1, 454 cm−1 and 502 cm−1 which may correspond to an atomic arrangement of tetrahedra of the type SiSiyO4−y where y ≠ 0 and y ≠ 1. The results contradict the mixture model (Si+SiO2) and show that the SiO oxide cannot be considered as a mixture of Si and SiO2. 相似文献
13.
基于Fermi黄金法则及Boltzmann方程碰撞项近似理论, 推导建立了(001)弛豫Si1-xGex衬底外延四方晶系应变Si空穴散射几率与应力及能量的理论关系模型, 包括离化杂质、声学声子、非极性光学声子及总散射概率(能量40 meV时)模型. 结果表明: 当Ge组分(x)低于0.2时, 应变Si/(001)Si1-xGex材料空穴总散射概率随应力显著减小. 之后, 其随应力的变化趋于平缓. 与立方晶系未应变Si材料相比, 四方晶系应变Si材料空穴总散射概率最多可减小66%. 应变Si材料空穴迁移率增强与其散射概率的减小密切相关, 本文所得量化模型可为应变Si空穴迁移率及PMOS器件的研究与设计提供理论参考. 相似文献
14.
Y.H. Luo J.L. Liu G. Jin J. Wan K.L. Wang 《Applied Physics A: Materials Science & Processing》2002,74(5):699-702
An effective compliant substrate for Si1-xGex growth is presented. A silicon-on-insulator substrate was implanted with B and O forming 20 wt % borosilicate glass within
the SiO2. The addition of the borosilicate glass to the buried oxide acted to reduce the viscosity at the growth temperature of Si1-xGex, promoting the in situ elastic deformation of the thin Si (∼20 nm) layer on the insulator. The sharing of the misfit between
the Si and the Si1-xGex layers was observed and quantified by double-axis X-ray diffraction. In addition, the material quality was assessed using
cross-sectional transmission electron microscopy, photoluminescence and etch pit density measurements. No misfit dislocations
were observed in the partially relaxed 150-nm Si0.75Ge0.25 sample as-grown on a 20% borosilicate glass substrate. The threading dislocation density was estimated at 2×104 cm-2 for 500-nm Si0.75Ge0.25 grown on the 20% borosilicate glass substrate. This method may be used to prepare compliant substrates for the growth of
low-dislocation relaxed SiGe layers.
Received: 4 January 2001 / Accepted: 30 May 2001 / Published online: 17 October 2001 相似文献
15.
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
16.
K. M. Gambaryan V. M. Aroutiounian A. K. Simonyan L. G. Movsesyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2012,47(4):173-180
The continuum elasticity model is applied to quantitatively investigate the growth features and nucleation mechanism of quantum dots (QDs), nanopits, and joint QDs-nanopits structures in SiGeC ternary systems. We determined the critical concentrations of carbon, x = 0.08 for Si1?x C x and y = 0.0033 for Si1?x?y Ge x C y at the concentration of germanium x = 0.467, when the growth mode changes from, respectively, nucleation of QDs to formation of nanopits. We have shown that the increase in the carbon concentration in a SiC binary system and of germanium concentration in a SiGeC ternary system leads to a decrease in the critical size of QD. The free energy of mixing for Si1?x?y Ge x C y ternary system was calculated and studied and its 3D sketch plotted. It is demonstrated that incorporation of carbon into Si and Ge up to background impurity concentration is energetically preferable, which explains the experimentally detected ??contamination?? of silicon and germanium crystals by carbon during the growth in the graphite crucible. 相似文献
17.
《Journal of magnetism and magnetic materials》2005,294(2):e151-e154
High-resolution X-ray diffraction patterns of Fe78.5Si20Ta1.5 and Fe80−xSi20Nbx (x=0.5, 3.0, 10) show the existence of a metastable hexagonal phase (NbFe2−xSix and TaFe2−xSix) together with bcc-Fe100−ySiy solid solution and an amorphous matrix. The grain size of the bcc-Fe100−ySiy phase decreases with increasing Nb content in Fe–Si compounds resulting in nanocrystalline materials. On the other side, the micro-strain, the lattice constant, coercivity and the Curie temperature increase with Nb concentration. Enhancements of the local strain and local magnetic anisotropy were also observed by means of NMR measurements. On the contrary, the addition of Cr causes a decrease in the coercivity and Curie temperature. 相似文献
18.
The electrical properties of p-type Ge, Ge1−ySny, and Si0.09Ge0.882Sn0.028 samples grown on n-type Si substrates using ultra-high vacuum chemical vapor deposition have been investigated as a function of temperature. Degenerate parallel conducting layers were found in all Ge/Si, Ge1−ySny/Si, and Si0.09Ge0.882Sn0.028/Si samples, which are believed to be associated with dislocation defects at the interface produced by the lattice mismatch between the two materials. These degenerate conducting layers affect the electrical properties of all the thin epitaxial films. Additionally, temperature dependent Hall-effect measurements show that these materials exhibit a conductivity type change from p to n at around 370–435 K. The mobilities of these samples are generally lower than that of bulk Ge due to carrier scattering near the interface between the epitaxial layer and the Si substrate and also due to alloy scattering. Detailed behavior of temperature-dependent conductivity of these samples is also discussed. 相似文献
19.
In the present paper, performance analysis of a resonant-cavity-enhanced Si/Si1–y
Ge
y
/Si multiple quantum well photodetector has been carried out. The effects of material parameters of active Si1–y
Ge
y
layers and carrier trapping by the potential barriers at the heterointerfaces of Si/Si1–y
Ge
y
/Si quantum wells on the bandwidth (BW) and Responsivity of the photodetector have been investigated using numerical simulation.
Results on possible optimum designs of the photodetector have been suggested to maximize BW-quantum efficiency product. 相似文献
20.
K. Koga 《Applied Physics A: Materials Science & Processing》1999,69(4):457-460
1-x-y GexCy have been grown on Si(100) substrates by rapid thermal chemical vapor deposition (RTCVD) using C2H4 as C source. The composition and microstructure of Si1-x-yGexCy films were characterized by Auger electron spectroscopy, Raman spectra and Fourier-transform infrared spectroscopy. The results
show that lower temperature and higher SiH4/C2H4 flow ratio are helpful in forming the substitutional C and improving the crystal quality. A possible mechanism for C incorporation
in Si1-x-yGexCy layers grown by RTCVD using C2H4 is proposed.
Received: 26 April 1998 / Accepted: 28 September 1998 / Published online: 24 February 1999 相似文献