TEM characterization of SiGeC material system

1994 ◽  
Vol 52 ◽  
pp. 840-841
Author(s):  
D. Chandrasekhar ◽  
David J. Smith ◽  
J. Kouvetakis ◽  
McD. Robinson
Keyword(s):  
Energy Gap ◽  
Compressive Strain ◽  
Compositional Analysis ◽  
Chemical Vapor ◽  
Standard Technique ◽  
Material System ◽  
Ion Milling ◽  
Bandgap Engineering ◽  
Si Substrates

The IV-IV material system, specifically Si1-xGex/Si, has generated considerable interest in the scientific community in recent years. The built-in compressive strain and composition of pseudomorphic Si1-xGex epilayers on Si substrates affect the band structure and energy gap, which are fundamental to bandgap engineering. This property has been used in demonstrating a heterojunction bipolar transistor with SiGe base, resulting in improved high-frequency performance over conventional transistors with Si bases. However, the thermal instability and lower critical thickness of Si1-xGex layers limits applications, in turn prompting investigation of the Si1-x-yGexCy system. Substitutional carbon incorporation in Si1-xGex is expected to relieve the strain in the epilayer and increase the energy gap, the latter being an important consideration in revolutionizing transistor technology. Recently, growth and characterization of pseudomorphic Si1-x-yGexCy and its photoluminescence properties have been reported.In our present study, we have characterized Si1-x-yGexCy samples grown on Si substrates by chemical vapor deposition. Different precursors and flow rates were used tovary the relative elemental compositions. Rutherford backscattering and secondary ion mass spectroscopy techniques were employed for compositional analysis and transmission electron microscopy was used to determine microstructure. Electron transparent specimens were prepared in cross-section by a standard technique, involving mechanical grinding, dimpling and argon ion-milling. TEM observations were made with JEOL 2000FX and JEOL 4000EX microscopes. Selected area diffraction patterns and optical diffractograms were used in determining the structure and lattice constants.

Characterization of GaAs films grown on Si substrates by molecular beam epitaxy

1988 ◽  
Vol 46 ◽  
pp. 896-897
Author(s):  
J.B. Posthill ◽  
J. Tarn ◽  
T.P. Humphreys ◽  
K. Das ◽  
J.J. Wortman ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Lattice Mismatch ◽  
Chemical Vapor ◽  
Antiphase Domain ◽  
Ex Situ ◽  
Material System ◽  
Bulk Gaas ◽  
Si Substrates

Because of several potential applications and advantages afforded by the heteroepitaxial GaAs-on-Silicon material system, several groups world-wide are attempting to grow device-quality GaAs on Si substrates.eg.1 Both metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) growth techniques have been widely utilized to achieve heteroepitaxial growth. However, certain fundamental materials and growth problems have thus far prevented any group from achieving heteroepitaxial GaAs of a quality similar to that obtainable from bulk GaAs crystals. A high density of threading dislocations, microtwins/stacking faults, antiphase domain boundaries (APBs) and microfissures can form under non-ideal conditions. These defects result, in part, from stresses generated due to the ∼4% lattice mismatch and the different coefficients of thermal expansion between GaAs and Si.2 Ex-situ characterization of this materials system is essential to assess the material quality and to provide direction for future growth experiments. This contribution describes the TEM characterization methodology that we employ to analyze our GaAs grown on Si substrates by MBE.

Characterization of Sil-ycy Alloy Layers Incorporating Si4c Building Blocks

1997 ◽  
Vol 3 (S2) ◽  
pp. 457-458
Author(s):  
D. Chandrasekhar ◽  
David J. Smith ◽  
J. Kouvetakis
Keyword(s):  
Band Gap ◽  
High Vacuum ◽  
Chemical Vapor ◽  
Building Blocks ◽  
Solubility Limit ◽  
Group Iv ◽  
Ultra High Vacuum ◽  
Material System ◽  
Si Substrates

Group IV based alloys have received considerable attention in recent years, because of the possibility to tailor the band gap of the material system with respect to that of Si. Significant results have already been achieved with Si-Ge system, where the band gap of pseudomorphic Si1-xGex alloys is smaller than that of Si. Introduction of C onto substitutional lattice sites in Si has been proposed as a possible alternate method for tailoring the electronic properties of Si. Carbon incorporation into Si substitutionally could result in alloys whose band gap would be a function of carbon concentration and lie between the values for silicon (E =1.1 eV) and β-SiC (Eg = 2.3 eV). However, due to the low-equilibrium solubility limit of C in Si, 3.5x1017cm−3 at the eutectic temperature, highly supersaturated and metastable layers are essential to significantly alter strain and electrical properties of the alloys.In our present study, we have synthesized and characterized Si1-yCy (0.04 < y < 0.20) films grown on (001) Si substrates by ultra-high vacuum chemical vapor deposition at 625°C.

scholarly journals Surface passivation and optical characterization of Al2O3/a-SiCx stacks on c-Si substrates

2013 ◽  
Vol 4 ◽  
pp. 726-731 ◽  
Author(s):  
Gema López ◽  
Pablo R Ortega ◽  
Cristóbal Voz ◽  
Isidro Martín ◽  
Mónica Colina ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Surface Passivation ◽  
Crystalline Silicon ◽  
Surface Recombination ◽  
Chemical Vapor ◽  
Optical Characterization ◽  
Surface Recombination Velocity ◽  
Carrier Injection ◽  
Si Substrates

The aim of this work is to study the surface passivation of aluminum oxide/amorphous silicon carbide (Al2O3/a-SiCx) stacks on both p-type and n-type crystalline silicon (c-Si) substrates as well as the optical characterization of these stacks. Al2O3 films of different thicknesses were deposited by thermal atomic layer deposition (ALD) at 200 °C and were complemented with a layer of a-SiCx deposited by plasma-enhanced chemical vapor deposition (PECVD) to form anti-reflection coating (ARC) stacks with a total thickness of 75 nm. A comparative study has been carried out on polished and randomly textured wafers. We have experimentally determined the optimum thickness of the stack for photovoltaic applications by minimizing the reflection losses over a wide wavelength range (300–1200 nm) without compromising the outstanding passivation properties of the Al2O3 films. The upper limit of the surface recombination velocity (S eff,max) was evaluated at a carrier injection level corresponding to 1-sun illumination, which led to values below 10 cm/s. Reflectance values below 2% were measured on textured samples over the wavelength range of 450–1000 nm.

Fabrication/Characterization of a Pseudomorphic Ga0.1In0.9P/InP MESFET

1993 ◽  
Vol 300 ◽  
Author(s):  
M. S. Feng ◽  
Y. M. Hsin ◽  
C. H. Wu
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Metalorganic Chemical Vapor Deposition ◽  
Energy Gap ◽  
Chemical Vapor ◽  
Drain Current ◽  
Low Pressure ◽  
Inp Substrate ◽  
Metalorganic Chemical

ABSTRACTA pseudomorphic Ga0.1In0.9P/InP MESFET grown by low pressure metalorganic chemical vapor deposition(LP-MOCVD) has been fabricated and characterized. The results indicated a transconductance of 66.7 ms/mm and a saturation drain current (Idss) of 55.6 mA have been achieved; furthermore, the Schottky barrier on InGaP as high as 0.67eV can be obtained using Pt2Si as the gate material. For comparison, a conventional InP MESFET with 5μm gate length has also been fabricated on InP epitaxial layer grown by low pressure metalorganic chemical vapor deposition on Fe-doped semi-insulating InP substrate. The transconductance and Idss were found to be 46.7 mS/mm and 43.1 mA at zero gate, respectively, for the depletion mode n-channel MESFET with Au as the gate metal; whereas, for the MESFET using Pt2Si as the gate metal, a transconductance of 40.3 mS/mm and a saturation drain current of 41.1 mA at zero gate bias have been obtained. The results indicated that Ga0.1In0.9P/lnP MESFET has better performance than InP MESFET because of higher energy gap of Ga0.1In0.9P.

Migration-Enhanced Molecular Beam Epitaxial Growth and Characterization of GaAs on Si Substrates

1988 ◽  
Vol 144 ◽  
Author(s):  
J.H. Kim ◽  
S. Sakai ◽  
J.K. Liu ◽  
G. Raohakrishnan ◽  
S.S. Chang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Organic Chemical ◽  
Cross Sectional ◽  
Light Emitting ◽  
Si Substrates ◽  
Molecular Beam Epitaxial

ABSTRACTWe first report on migration-enhanced molecular beam epitaxial (MEMBE) growth and characterization of the GaAs layers on Si substrates (GaAs/Si). Excellent surface morphology GaAs layers were successfully grown on (100) Sisubstrates misoriented 4 toward [110] direction. The MEMBE growth method isdescribed and material properties are compared with those of normal two-step MBE-grown or in-situ annealed layers. Micrographs of cross-sectional view transmission electron microscopy (TEM) and scanning surface electron microscopy (SEM) of MEMBE-grown GaAs/Si showed dislocation densities of 107 cm-2 over ten times lower than those of two-step MBE-grown or in-situ annealedlayers. AlGaAs/GaAs double heterostructure lasers and light-emitting diodeshave been successfully grown on MEMBE GaAs/Si by both metal organic chemical vapor deposition and liquid phase epitaxy. MOCVD-grown lasers showed peak output power as high as 184 mW/facet, pulsed threshold currents as low as150 mA at 300 K, and differential quantum efficiencies of up to 30 %. The LPE-grown light-emitting diodes showed output powers of 1.5 mW and external quantum efficiencies of 3.3 mW/A per facet.

scholarly journals Facile and Controllable Synthesis of Large-Area Monolayer WS2 Flakes Based on WO3 Precursor Drop-Casted Substrates by Chemical Vapor Deposition

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 578 ◽  
Author(s):  
Biao Shi ◽  
Daming Zhou ◽  
Shaoxi Fang ◽  
Khouloud Djebbi ◽  
Shuanglong Feng ◽  
...  
Keyword(s):  
Energy Gap ◽  
Growth Parameters ◽  
Fluorescence Emission ◽  
Chemical Vapor ◽  
Optical Microscope ◽  
Edge Length ◽  
Controllable Synthesis ◽  
Large Area ◽  
Si Substrates ◽  
Potential Applications

Monolayer WS2 (Tungsten Disulfide) with a direct-energy gap and excellent photoluminescence quantum yield at room temperature shows potential applications in optoelectronics. However, controllable synthesis of large-area monolayer WS2 is still challenging because of the difficulty in controlling the interrelated growth parameters. Herein, we report a facile and controllable method for synthesis of large-area monolayer WS2 flakes by direct sulfurization of powdered WO3 (Tungsten Trioxide) drop-casted on SiO2/Si substrates in a one-end sealed quartz tube. The samples were thoroughly characterized by an optical microscope, atomic force microscope, transmission electron microscope, fluorescence microscope, photoluminescence spectrometer, and Raman spectrometer. The obtained results indicate that large triangular monolayer WS2 flakes with an edge length up to 250 to 370 μm and homogeneous crystallinity were readily synthesized within 5 min of growth. We demonstrate that the as-grown monolayer WS2 flakes show distinctly size-dependent fluorescence emission, which is mainly attributed to the heterogeneous release of intrinsic tensile strain after growth.

Epitaxial Realignment of In-Situ Doped Polycrystalline Silicon for Advanced BiCMOS Technologies

1999 ◽  
Vol 587 ◽  
Author(s):  
K. Chang ◽  
S.G. Thomas ◽  
T-C. Lee ◽  
R.B. Gregory ◽  
D. O'meara ◽  
...  
Keyword(s):  
Polycrystalline Silicon ◽  
Chemical Vapor ◽  
Layer Growth ◽  
Native Oxide ◽  
Post Deposition Annealing ◽  
Si Substrates ◽  
Si Films ◽  
Post Deposition

AbstractIndustrial feasibility of an in-situ-doped (ISD) polycrystalline Si process using chemical vapor deposition for advanced BiCMOS technologies is presented. ISD As-doped amorphous and polycrystalline Si layers have been deposited on Si substrates at 610°C and 660°C, respectively, with the deposition rate varying from 120 to 128Å /minute. Samples are compared on the basis of having been subjected to a substrate preclean prior to deposition using an HF solution and an in-situ H2 bake. TEM micrographs reveal the presence of a thin (10-15 Å) native oxide at the deposited layer/substrate interface for samples not precleaned. This is confirmed for both the amorphous and polycrystalline Si depositions. However, for the 610°C-deposited samples given the substrate preclean, a polycrystalline structure with partial epitaxial layer growth is observed. Twins and stacking faults are found at the poly Si/single crystal Si interface, causing interfacial roughness. Post-deposition annealing of the Si films typically generates grain growth, but RBS-channeling characterization of the annealed Si provides evidence of some recrystallization, the extent of which is affected by the original growth condition. Analysis shows that the amorphous deposition at 610°C results in a mixture of epitaxial and polycrystalline Si. Epitaxial realignment of the polycrystalline Si film by post deposition annealing can result in significantly improved device performance.

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