The fabrication and characterization of strained-Si material grown on a relaxed Si0.79 Ge0.21/graded Si1-x- Gex/Si virtual substrate, using reduced pressure chemical vapor deposition, are presented. The Ge concentrati...The fabrication and characterization of strained-Si material grown on a relaxed Si0.79 Ge0.21/graded Si1-x- Gex/Si virtual substrate, using reduced pressure chemical vapor deposition, are presented. The Ge concentration of the constant composition SiGe layer and the grading rate of the graded SiGe layer are estimated with double-crystal X-ray diffraction and further confirmed by SIMS measurements. The surface root mean square roughness of the strained Si cap layer is 2.36nm,and the strain is about 0.83% as determined by atomic force microscopy and Raman spectra, respectively. The threading dislocation density is on the order of 4 × 10^4cm^-2. Furthermore, it is found that the stress in the strained Si cap layer is maintained even after the high thermal budget process, nMOSFET devices are fabricated and measured in strained-Si and unstrained bulk-Si channels. Compared to the co-processed bulk-Si MOSFETs at room temperature,a significant low vertical field mobility enhancement of about 85% is observed in the strained-Si devices.展开更多
An analytical model of electron mobility for strained-silicon channel nMOSFETs is proposed in this paper. The model deals directly with the strain tensor,and thus is independent of the manufacturing process. It is sui...An analytical model of electron mobility for strained-silicon channel nMOSFETs is proposed in this paper. The model deals directly with the strain tensor,and thus is independent of the manufacturing process. It is suitable for （100〉/ 〈110） channel nMOSFETs under biaxial or （100〉/〈 110 ） uniaxial stress and can be implemented in conventional device simulation tools .展开更多
The process parameters are adjusted and the process procedure is simplified on the basis of precursor's work and the strained Si channel SiGe n MOSFET is fabricated successfully.This n MOSFET takes the strained...The process parameters are adjusted and the process procedure is simplified on the basis of precursor's work and the strained Si channel SiGe n MOSFET is fabricated successfully.This n MOSFET takes the strained Si layer(which is deposited on the relaxed SiGe buffer layer) as current channel and can provide a 48 5% improvement in electron mobility while keeping the gate voltage as 1V.展开更多
The strain Lv（1- z） isolated from the Henan bauxite was characterized by morphological observation, biochemical and physiological identification, and 16S rDNA sequence analysis. The influences of temperature, initia...The strain Lv（1- z） isolated from the Henan bauxite was characterized by morphological observation, biochemical and physiological identification, and 16S rDNA sequence analysis. The influences of temperature, initial pH value, the volume of medium, shaking speed and illite concentration on the desilicating ability of the strain Lv（1- z） were investigated. The results show that the bacterium is a Gram-negative rod-shaped bacterium with oval endspores and thick capsule, but without flagellum. The biochemical and physiological tests indicate that the strain Lv（1- z） is similar to Bacillus rnucilaginosus. In GenBank the 16S rDNA sequence similarity of the strain Lv（1- z） and the B. rnucilaginosus YNUCC0001（AY571332） is more than 99%. Based on the above results, the strain Lv（1- z） is identified as B. rnucilaginosus. The optimum conditions for the strain L（1- z） to remove silicon from illite are as follows., temperature is 30℃ ;initial pH value is 7.5; medium volume in 200 mL bottle is 60 mL; shaking speed of rotary shaker is 220 r/m ; illite concentration is 1%.展开更多
Doped micro-crystalline silicon films are deposited at temperatures as low as 400 ℃ by the catalytic chemical vapor deposition method using a silane and hydrogen gas mixture. Electrical properties such as the carrier...Doped micro-crystalline silicon films are deposited at temperatures as low as 400 ℃ by the catalytic chemical vapor deposition method using a silane and hydrogen gas mixture. Electrical properties such as the carrier concentration and the Hall mobility are investigated for various measuring temperatures. It is found that the grains of micro-crystalline silicon are preferentially oriented along the (220) direction , and that the Hall mobility is larger than 8 cm 2·V -1 ·s -1 , the carrier concentration is about 1×10 17 cm -1 ～1×10 19 cm -3 at room temperature.展开更多
Biaxial strain technology is a promising way to improve the mobility of both electrons and holes, while （100） channel direction appears as to be an effective booster of hole mobility in particular. In this work, the...Biaxial strain technology is a promising way to improve the mobility of both electrons and holes, while （100） channel direction appears as to be an effective booster of hole mobility in particular. In this work, the impact of biaxial strain together with （100） channel orientation on hole mobility is explored. The biaxial strain was incorporated by the growth of a relaxed SiGe buffer layer,serving as the template for depositing a Si layer in a state of biaxial tensile strain. The channel orientation was implemented with a 45^o rotated design in the device layout,which changed the channel direction from （110） to （100） on Si （001） surface. The maximum hole mobility is enhanced by 30% due to the change of channel direction from （110） to （100） on the same strained Si （s-Si） p-MOSFETs,in addition to the mobility enhancement of 130% when comparing s-Si pMOS to bulk Si pMOS both along （110） channels. Discussion and analysis are presented about the origin of the mobility enhancement by channel orientation along with biaxial strain in this work.展开更多
The carrier mobility of Si material can be enhanced under strain,and the stress magnitude can be measured by the Raman spectrum.In this paper,we aim to study the penetration depths into biaxially-strained Si materials...The carrier mobility of Si material can be enhanced under strain,and the stress magnitude can be measured by the Raman spectrum.In this paper,we aim to study the penetration depths into biaxially-strained Si materials at various Raman excitation wavelengths and the stress model corresponding to Raman spectrum in biaxially-strained Si.The experimental results show that it is best to use 325 nm excitation to measure the material stress in the top strained Si layer,and that one must pay attention to the distortion of the buffer layers on measuring results while 514 nm excitation is also measurable.Moreover,we established the stress model for Raman spectrum of biaxially-strained Si based on the Secular equation.One can obtain the stress magnitude in biaxially-strained Si by the model,as long as the results of the Raman spectrum are given.Our quantitative results can provide valuable references for stress analysis on strained materials.展开更多
Metamorphic Al0.50In0.50As/Ga0.47In0.53As high electron mobility transistors (mHEMTs) grown by Metal Organic ChemicalVapor Deposition (MOCVD) on n-type silicon substrates with introduction of a novel multi-stage buffe...Metamorphic Al0.50In0.50As/Ga0.47In0.53As high electron mobility transistors (mHEMTs) grown by Metal Organic ChemicalVapor Deposition (MOCVD) on n-type silicon substrates with introduction of a novel multi-stage buffering stack scheme havebeen fabricated for the first time. 1.0- m-gate-length depletion-mode mHEMTs with maximum transconductance up to 613mS/mm are achieved. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) are 36.9 and55.6 GHz, respectively. This device has the highest fTyet reported for 1.0- m-gate-length HEMTs grown on silicon byMOCVD. Also, this performance is comparable to that of similar GaAs-based mHEMTs. These are encouraging initial resultsleading to the manufacturing potential of integrated high-speed metamorphic devices for logic applications on silicon sub-strates by MOCVD.展开更多
The effect of ground granulated blast-furnace slag(GGBFS) and silica fume(SF) on the chloride migration through concrete subjected to repeated loading was examined.Portland cement was replaced by 20%,30%,40% GGBFS and...The effect of ground granulated blast-furnace slag(GGBFS) and silica fume(SF) on the chloride migration through concrete subjected to repeated loading was examined.Portland cement was replaced by 20%,30%,40% GGBFS and 5%,10% SF,respectively.Five times repeated loadings were applied to specimens,the maximum loadings were 40% and 80% of the axial cylinder compressive strength(f′c),respectively.Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured.The results indicate that the transport number of chloride through concrete containing 20% and 30% GGBFS replacements and 5% and 10% SF replacements is lower than that of the control concrete,but 40% GGBFS replacement increases the transport number of chloride.Five loadings at 40% f′cor 80% f′c increase the transport number of chloride for all mixes investigated in this study.5% SF replacement has a very close effect on the chloride permeability of concrete with 20% GGBFS when concrete is subjected to 40% f′cor 80% f′c.展开更多
The hole mobility of strained silicon along the <110> orientation on (001) Si1?xGex is obtained by solving collision term in the Boltzmann transport equation. The analytical model is proposed that considers the ...The hole mobility of strained silicon along the <110> orientation on (001) Si1?xGex is obtained by solving collision term in the Boltzmann transport equation. The analytical model is proposed that considers the effect of strain-induced splitting at valence band valleys in silicon, doping dependence and three scattering mechanisms, i.e., ionized impurity scattering, acoustic phonon scattering and non-polar optical phonon scattering. The hole occupancy at top band indicates a non-monotonic variation under biaxial tensile strain at low temperature (77 K). What's more, a non-monotonic variation of hole mobility at room temperature (300 K) is presented. Compared with the room temperature hole mobility, the low temperature hole mobility is affected greatly by ionized impurity scattering at lower impurity concentration. At the same time, the room temperature hole mobility is lower than that of electron with the same germanium content and doping concentration. If the parameters are correctly chosen, the model can also be used to calculate the hole mobility of other crystal faces with arbitrary orientation. So, it lays a useful foundation for strained silicon devices and circuits.展开更多
We present an InGaAs metamorphic high electron mobility transistor （mHEMT） grown using Metalorganic Chemical Vapor Deposition （MOCVD） on an n-type silicon substrate with the introduction of an effective multi-stag...We present an InGaAs metamorphic high electron mobility transistor （mHEMT） grown using Metalorganic Chemical Vapor Deposition （MOCVD） on an n-type silicon substrate with the introduction of an effective multi-stage buffering scheme. Fabrication and performance of a high-frequency 0.3μm gate-length depletion-mode A10.s0In0.s0As/Ga0.47In0.53As mHEMT is re- ported for the first time. Using a combined optical and e-beam photolithography technology, submicron mHEMT devices on Si have been achieved. The non-alloyed ohmic contact resistance Rc was as low as 0.065 Ω-mm. A maximum transconductance up to 761 mS/ram was measured. The unity current gain cut-off frequency （fT） and the maximum oscillation frequency （fmax） were 72.8 and 74.5 GHz, respectively. This device has the highest fw yet reported for a 0.3-μm gate-length Si-based mHEMT grown using MOCVD. A high voltage gain, gm/gds, of 40.6 is observed in the device.展开更多
文摘The fabrication and characterization of strained-Si material grown on a relaxed Si0.79 Ge0.21/graded Si1-x- Gex/Si virtual substrate, using reduced pressure chemical vapor deposition, are presented. The Ge concentration of the constant composition SiGe layer and the grading rate of the graded SiGe layer are estimated with double-crystal X-ray diffraction and further confirmed by SIMS measurements. The surface root mean square roughness of the strained Si cap layer is 2.36nm,and the strain is about 0.83% as determined by atomic force microscopy and Raman spectra, respectively. The threading dislocation density is on the order of 4 × 10^4cm^-2. Furthermore, it is found that the stress in the strained Si cap layer is maintained even after the high thermal budget process, nMOSFET devices are fabricated and measured in strained-Si and unstrained bulk-Si channels. Compared to the co-processed bulk-Si MOSFETs at room temperature,a significant low vertical field mobility enhancement of about 85% is observed in the strained-Si devices.
文摘An analytical model of electron mobility for strained-silicon channel nMOSFETs is proposed in this paper. The model deals directly with the strain tensor,and thus is independent of the manufacturing process. It is suitable for （100〉/ 〈110） channel nMOSFETs under biaxial or （100〉/〈 110 ） uniaxial stress and can be implemented in conventional device simulation tools .
文摘The process parameters are adjusted and the process procedure is simplified on the basis of precursor's work and the strained Si channel SiGe n MOSFET is fabricated successfully.This n MOSFET takes the strained Si layer(which is deposited on the relaxed SiGe buffer layer) as current channel and can provide a 48 5% improvement in electron mobility while keeping the gate voltage as 1V.
基金Project (50321402) supported by the National Natural Science Foundation of China project (2004CB619204) supportedby the National Basic Research Program
文摘The strain Lv（1- z） isolated from the Henan bauxite was characterized by morphological observation, biochemical and physiological identification, and 16S rDNA sequence analysis. The influences of temperature, initial pH value, the volume of medium, shaking speed and illite concentration on the desilicating ability of the strain Lv（1- z） were investigated. The results show that the bacterium is a Gram-negative rod-shaped bacterium with oval endspores and thick capsule, but without flagellum. The biochemical and physiological tests indicate that the strain Lv（1- z） is similar to Bacillus rnucilaginosus. In GenBank the 16S rDNA sequence similarity of the strain Lv（1- z） and the B. rnucilaginosus YNUCC0001（AY571332） is more than 99%. Based on the above results, the strain Lv（1- z） is identified as B. rnucilaginosus. The optimum conditions for the strain L（1- z） to remove silicon from illite are as follows., temperature is 30℃ ;initial pH value is 7.5; medium volume in 200 mL bottle is 60 mL; shaking speed of rotary shaker is 220 r/m ; illite concentration is 1%.
基金The National Science Foundation of China under Grant
文摘Doped micro-crystalline silicon films are deposited at temperatures as low as 400 ℃ by the catalytic chemical vapor deposition method using a silane and hydrogen gas mixture. Electrical properties such as the carrier concentration and the Hall mobility are investigated for various measuring temperatures. It is found that the grains of micro-crystalline silicon are preferentially oriented along the (220) direction , and that the Hall mobility is larger than 8 cm 2·V -1 ·s -1 , the carrier concentration is about 1×10 17 cm -1 ～1×10 19 cm -3 at room temperature.
文摘Biaxial strain technology is a promising way to improve the mobility of both electrons and holes, while （100） channel direction appears as to be an effective booster of hole mobility in particular. In this work, the impact of biaxial strain together with （100） channel orientation on hole mobility is explored. The biaxial strain was incorporated by the growth of a relaxed SiGe buffer layer,serving as the template for depositing a Si layer in a state of biaxial tensile strain. The channel orientation was implemented with a 45^o rotated design in the device layout,which changed the channel direction from （110） to （100） on Si （001） surface. The maximum hole mobility is enhanced by 30% due to the change of channel direction from （110） to （100） on the same strained Si （s-Si） p-MOSFETs,in addition to the mobility enhancement of 130% when comparing s-Si pMOS to bulk Si pMOS both along （110） channels. Discussion and analysis are presented about the origin of the mobility enhancement by channel orientation along with biaxial strain in this work.
基金supported by the Research Fund for the Doctoral Program of Higher Education of China(Grant No.JY0300122503)the NLAIC Research Fund(Grant No.P140c090303110c0904)
文摘The carrier mobility of Si material can be enhanced under strain,and the stress magnitude can be measured by the Raman spectrum.In this paper,we aim to study the penetration depths into biaxially-strained Si materials at various Raman excitation wavelengths and the stress model corresponding to Raman spectrum in biaxially-strained Si.The experimental results show that it is best to use 325 nm excitation to measure the material stress in the top strained Si layer,and that one must pay attention to the distortion of the buffer layers on measuring results while 514 nm excitation is also measurable.Moreover,we established the stress model for Raman spectrum of biaxially-strained Si based on the Secular equation.One can obtain the stress magnitude in biaxially-strained Si by the model,as long as the results of the Raman spectrum are given.Our quantitative results can provide valuable references for stress analysis on strained materials.
文摘Metamorphic Al0.50In0.50As/Ga0.47In0.53As high electron mobility transistors (mHEMTs) grown by Metal Organic ChemicalVapor Deposition (MOCVD) on n-type silicon substrates with introduction of a novel multi-stage buffering stack scheme havebeen fabricated for the first time. 1.0- m-gate-length depletion-mode mHEMTs with maximum transconductance up to 613mS/mm are achieved. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) are 36.9 and55.6 GHz, respectively. This device has the highest fTyet reported for 1.0- m-gate-length HEMTs grown on silicon byMOCVD. Also, this performance is comparable to that of similar GaAs-based mHEMTs. These are encouraging initial resultsleading to the manufacturing potential of integrated high-speed metamorphic devices for logic applications on silicon sub-strates by MOCVD.
基金supported by the National Natural Science Foundation of China (Grant No.50808045)Natural Science Foundation of Beijing(Grant No.2112024)Fok Ying Tung Education Foundation (GrantNo.132016)
文摘The effect of ground granulated blast-furnace slag(GGBFS) and silica fume(SF) on the chloride migration through concrete subjected to repeated loading was examined.Portland cement was replaced by 20%,30%,40% GGBFS and 5%,10% SF,respectively.Five times repeated loadings were applied to specimens,the maximum loadings were 40% and 80% of the axial cylinder compressive strength(f′c),respectively.Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured.The results indicate that the transport number of chloride through concrete containing 20% and 30% GGBFS replacements and 5% and 10% SF replacements is lower than that of the control concrete,but 40% GGBFS replacement increases the transport number of chloride.Five loadings at 40% f′cor 80% f′c increase the transport number of chloride for all mixes investigated in this study.5% SF replacement has a very close effect on the chloride permeability of concrete with 20% GGBFS when concrete is subjected to 40% f′cor 80% f′c.
基金supported by the National Ministries and Commissions (Grant Nos. 51308040203, 9140A08060407DZ0103 and 6139801)
文摘The hole mobility of strained silicon along the <110> orientation on (001) Si1?xGex is obtained by solving collision term in the Boltzmann transport equation. The analytical model is proposed that considers the effect of strain-induced splitting at valence band valleys in silicon, doping dependence and three scattering mechanisms, i.e., ionized impurity scattering, acoustic phonon scattering and non-polar optical phonon scattering. The hole occupancy at top band indicates a non-monotonic variation under biaxial tensile strain at low temperature (77 K). What's more, a non-monotonic variation of hole mobility at room temperature (300 K) is presented. Compared with the room temperature hole mobility, the low temperature hole mobility is affected greatly by ionized impurity scattering at lower impurity concentration. At the same time, the room temperature hole mobility is lower than that of electron with the same germanium content and doping concentration. If the parameters are correctly chosen, the model can also be used to calculate the hole mobility of other crystal faces with arbitrary orientation. So, it lays a useful foundation for strained silicon devices and circuits.
基金supported by the CERG(Grant No. 615506) from the Research Grants Council of Hong Kong and Intel Corporation
文摘We present an InGaAs metamorphic high electron mobility transistor （mHEMT） grown using Metalorganic Chemical Vapor Deposition （MOCVD） on an n-type silicon substrate with the introduction of an effective multi-stage buffering scheme. Fabrication and performance of a high-frequency 0.3μm gate-length depletion-mode A10.s0In0.s0As/Ga0.47In0.53As mHEMT is re- ported for the first time. Using a combined optical and e-beam photolithography technology, submicron mHEMT devices on Si have been achieved. The non-alloyed ohmic contact resistance Rc was as low as 0.065 Ω-mm. A maximum transconductance up to 761 mS/ram was measured. The unity current gain cut-off frequency （fT） and the maximum oscillation frequency （fmax） were 72.8 and 74.5 GHz, respectively. This device has the highest fw yet reported for a 0.3-μm gate-length Si-based mHEMT grown using MOCVD. A high voltage gain, gm/gds, of 40.6 is observed in the device.
