Relationship between the hole concentration at room temperature and the Mg doping concentration in p-GaN grown by MOCVD after sufficient annealing was studied in this paper.Different annealing conditions were applied ...Relationship between the hole concentration at room temperature and the Mg doping concentration in p-GaN grown by MOCVD after sufficient annealing was studied in this paper.Different annealing conditions were applied to obtain sufficient activation for p-GaN samples with different Mg doping ranges.Hole concentration,resistivity and mobility were characterized by room-temperature Hall measurements.The Mg doping concentration and the residual impurities such as H,C,O and Si were measured by secondary ion mass spectroscopy,confirming negligible compensations by the impurities.The hole concentration,resistivity and mobility data are presented as a function of Mg concentration,and are compared with literature data.The appropriate curve relating the Mg doping concentration to the hole concentration is derived using a charge neutrality equation and the ionized-acceptor-density[N-(A)^(-)](cm^(−3))dependent ionization energy of Mg acceptor was determined asE_(A)^(Mg)=184−2.66×10^(−5)×[N_(A)^(-)]1/3 meV.展开更多
In this paper, based upon the basic solution of sink, the approximate solution of single drain hole in finite elements is derived by use of the superposition principle. Then, the theoretical solution is extended to th...In this paper, based upon the basic solution of sink, the approximate solution of single drain hole in finite elements is derived by use of the superposition principle. Then, the theoretical solution is extended to the case of some drain holes in one finite element, and the method is used in seepage control analysis with quick convergence and high accuracy. On the other hand, if the positions of the drain holes are changed, only some control factors of drain holes are changed, but the finite element grid need not to be reformed. Therefore, the method is more suitable in optimal research of seepage control.展开更多
This study proposes a parameterized model of a uniaxial symmetry non-circular hole, to improve conventional circular bolt clearance holes on turbine disks. The profile of the model consists of eight smoothly connected...This study proposes a parameterized model of a uniaxial symmetry non-circular hole, to improve conventional circular bolt clearance holes on turbine disks. The profile of the model consists of eight smoothly connected arcs, the radiuses of which are determined by 5 design variables.By changing the design variables, the profile of the non-circular hole can be transformed to accommodate different load ratios, thereby improving the stress concentration of the area near the hole and that of the turbine disk. The uniaxial symmetry non-circular hole is optimized based on finite element method(FEM), in which the maximum first principal stress is taken as the objective function. After optimization, the stress concentration is evidently relieved; the maximum first principal stress and the maximum von Mises stress on the critical area are reduced by 30.39% and 25.34%respectively, showing that the uniaxial symmetry non-circular hole is capable of reducing the stress level of bolt clearance holes on the turbine disk.展开更多
The impact of the fraction of germanium on the carrier performance of two-dimensional strained silicon, which embraces both the non-degenerate and degenerate regimes,is developed.In this model,the Fermi integral of or...The impact of the fraction of germanium on the carrier performance of two-dimensional strained silicon, which embraces both the non-degenerate and degenerate regimes,is developed.In this model,the Fermi integral of order zero is employed.The impact of the fraction of germanium on the relaxed Si_(1-x)Ge_x substrate(x),carrier concentration and temperature is reported.It is revealed that the effect of x on the hole concentration is dominant for a normalized Fermi energy of more than three,or in other words the non-degenerate regime.On the contrary, the x gradient has less influence in the degenerate regime.Furthermore,by increasing x there is an increase in the intrinsic velocity,particularly with high carrier concentration and temperature.展开更多
Thermoelectric properties of spark-plasma-sintering prepared bulk materials EuxNay□zSn1–x–y–zTe above room temperature were investigated. The implementation of Eu and Na into the SnTe lattice was monitored by refi...Thermoelectric properties of spark-plasma-sintering prepared bulk materials EuxNay□zSn1–x–y–zTe above room temperature were investigated. The implementation of Eu and Na into the SnTe lattice was monitored by refinement of lattice parameters as well as energy dispersive X-ray spectroscopy(EDXS). The binary SnTe achieved the highest ZT value of 0.63 at 786 K, and showed a hole concentration of 4.6′10^19 cm^–3 at 300 K. In comparison with pristine SnTe, the samples containing Eu had lower carrier mobility but higher Hall carrier concentration. For Eu- and Na-substituted samples, the increased hole concentration was unfavorable for the improvement of thermoelectric properties.展开更多
基金supported by the National Natural Science Foundation of China(62150710548,61834008,U21A20493)the National Key Research and Development Program of China(2022YFB2802801)+2 种基金the Key Research and Development Program of Jiangsu Province(BE2021008-1)the Suzhou Key Laboratory of New-type Laser Display Technology(SZS2022007)the Natural Science Foundation of Jiangsu Province(BK20232042).
文摘Relationship between the hole concentration at room temperature and the Mg doping concentration in p-GaN grown by MOCVD after sufficient annealing was studied in this paper.Different annealing conditions were applied to obtain sufficient activation for p-GaN samples with different Mg doping ranges.Hole concentration,resistivity and mobility were characterized by room-temperature Hall measurements.The Mg doping concentration and the residual impurities such as H,C,O and Si were measured by secondary ion mass spectroscopy,confirming negligible compensations by the impurities.The hole concentration,resistivity and mobility data are presented as a function of Mg concentration,and are compared with literature data.The appropriate curve relating the Mg doping concentration to the hole concentration is derived using a charge neutrality equation and the ionized-acceptor-density[N-(A)^(-)](cm^(−3))dependent ionization energy of Mg acceptor was determined asE_(A)^(Mg)=184−2.66×10^(−5)×[N_(A)^(-)]1/3 meV.
文摘In this paper, based upon the basic solution of sink, the approximate solution of single drain hole in finite elements is derived by use of the superposition principle. Then, the theoretical solution is extended to the case of some drain holes in one finite element, and the method is used in seepage control analysis with quick convergence and high accuracy. On the other hand, if the positions of the drain holes are changed, only some control factors of drain holes are changed, but the finite element grid need not to be reformed. Therefore, the method is more suitable in optimal research of seepage control.
基金co-supported by Aeronautical Science Foundation of China (No. 2012ZB52028)the Fundamental Research Funds for the Central Universities of China (No. NZ2012105)
文摘This study proposes a parameterized model of a uniaxial symmetry non-circular hole, to improve conventional circular bolt clearance holes on turbine disks. The profile of the model consists of eight smoothly connected arcs, the radiuses of which are determined by 5 design variables.By changing the design variables, the profile of the non-circular hole can be transformed to accommodate different load ratios, thereby improving the stress concentration of the area near the hole and that of the turbine disk. The uniaxial symmetry non-circular hole is optimized based on finite element method(FEM), in which the maximum first principal stress is taken as the objective function. After optimization, the stress concentration is evidently relieved; the maximum first principal stress and the maximum von Mises stress on the critical area are reduced by 30.39% and 25.34%respectively, showing that the uniaxial symmetry non-circular hole is capable of reducing the stress level of bolt clearance holes on the turbine disk.
基金the financial support from the National Science Foundation(NSF) grant of the Ministry of Higher Education(MOHE),Malaysia
文摘The impact of the fraction of germanium on the carrier performance of two-dimensional strained silicon, which embraces both the non-degenerate and degenerate regimes,is developed.In this model,the Fermi integral of order zero is employed.The impact of the fraction of germanium on the relaxed Si_(1-x)Ge_x substrate(x),carrier concentration and temperature is reported.It is revealed that the effect of x on the hole concentration is dominant for a normalized Fermi energy of more than three,or in other words the non-degenerate regime.On the contrary, the x gradient has less influence in the degenerate regime.Furthermore,by increasing x there is an increase in the intrinsic velocity,particularly with high carrier concentration and temperature.
基金supported by Young Eastern Scholar Project of Shanghai Municipal Education Commission(QD2015031)
文摘Thermoelectric properties of spark-plasma-sintering prepared bulk materials EuxNay□zSn1–x–y–zTe above room temperature were investigated. The implementation of Eu and Na into the SnTe lattice was monitored by refinement of lattice parameters as well as energy dispersive X-ray spectroscopy(EDXS). The binary SnTe achieved the highest ZT value of 0.63 at 786 K, and showed a hole concentration of 4.6′10^19 cm^–3 at 300 K. In comparison with pristine SnTe, the samples containing Eu had lower carrier mobility but higher Hall carrier concentration. For Eu- and Na-substituted samples, the increased hole concentration was unfavorable for the improvement of thermoelectric properties.