A two-dimensional （2D） full band self-consistent ensemble Monte Carlo （MC） method for solving the quantum Boltzmann equation, including collision broadening and quantum potential corrections, is developed to exten...A two-dimensional （2D） full band self-consistent ensemble Monte Carlo （MC） method for solving the quantum Boltzmann equation, including collision broadening and quantum potential corrections, is developed to extend the MC method to the study of nano-scale semiconductor devices with obvious quantum mechanical （QM） effects. The quantum effects both in real space and momentum space in nano-scale semiconductor devices can be simulated. The effective mobility in the inversion layer of n and p channel MOSFET is simulated and compared with experimental data to verify this method. With this method 50nm ultra thin body silicon on insulator MOSFET are simulated. Results indicate that this method can be used to simulate the 2D QM effects in semiconductor devices including tunnelling effect.展开更多
Characteristic finite difference fractional step schemes are put forward. The electric potential equation is described by a seven-point finite difference scheme, and the electron and hole concentration equations are t...Characteristic finite difference fractional step schemes are put forward. The electric potential equation is described by a seven-point finite difference scheme, and the electron and hole concentration equations are treated by a kind of characteristic finite difference fractional step methods. The temperature equation is described by a fractional step method. Thick and thin grids are made use of to form a complete set. Piecewise threefold quadratic interpolation, symmetrical extension, calculus of variations, commutativity of operator product, decomposition of high order difference operators and prior estimates are also made use of. Optimal order estimates in l2 norm are derived to determine the error of the approximate solution. The well-known problem is thorongley and completely solred.展开更多
The effect of nitric oxide（NO） annealing on charge traps in the oxide insulator and transition layer in n-type4H–Si C metal–oxide–semiconductor（MOS） devices has been investigated using the time-dependent bias s...The effect of nitric oxide（NO） annealing on charge traps in the oxide insulator and transition layer in n-type4H–Si C metal–oxide–semiconductor（MOS） devices has been investigated using the time-dependent bias stress（TDBS）,capacitance–voltage（C–V）,and secondary ion mass spectroscopy（SIMS）.It is revealed that two main categories of charge traps,near interface oxide traps（Nniot） and oxide traps（Not）,have different responses to the TDBS and C–V characteristics in NO-annealed and Ar-annealed samples.The Nniotare mainly responsible for the hysteresis occurring in the bidirectional C–V characteristics,which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor.However,Not is mainly responsible for the TDBS induced C–V shifts.Electrons tunneling into the Not are hardly released quickly when suffering TDBS,resulting in the problem of the threshold voltage stability.Compared with the Ar-annealed sample,Nniotcan be significantly suppressed by the NO annealing,but there is little improvement of Not.SIMS results demonstrate that the Nniotare distributed within the transition layer,which correlated with the existence of the excess silicon.During the NO annealing process,the excess Si atoms incorporate into nitrogen in the transition layer,allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot.展开更多
The transient behavior of a semiconductor device consists of a Poisson equation for the electric potential and of two nonlinear parabolic equations for the electron density and hole density. The electric potential equ...The transient behavior of a semiconductor device consists of a Poisson equation for the electric potential and of two nonlinear parabolic equations for the electron density and hole density. The electric potential equation is discretized by a mixed finite element method. The electron and hole density equations are treated by implicit-explicit multistep finite element methods. The schemes are very efficient. The optimal order error estimates both in time and space are derived.展开更多
The numerical simulation of a three-dimensional semiconductor device is a fundamental problem in information science. The mathematical model is defined by an initialboundary nonlinear system of four partial differenti...The numerical simulation of a three-dimensional semiconductor device is a fundamental problem in information science. The mathematical model is defined by an initialboundary nonlinear system of four partial differential equations: an elliptic equation for electric potential, two convection-diffusion equations for electron concentration and hole concentration, and a heat conduction equation for temperature. The first equation is solved by the conservative block-centered method. The concentrations and temperature are computed by the block-centered upwind difference method on a changing mesh, where the block-centered method and upwind approximation are used to discretize the diffusion and convection, respectively. The computations on a changing mesh show very well the local special properties nearby the P-N junction. The upwind scheme is applied to approximate the convection, and numerical dispersion and nonphysical oscillation are avoided. The block-centered difference computes concentrations, temperature, and their adjoint vector functions simultaneously.The local conservation of mass, an important rule in the numerical simulation of a semiconductor device, is preserved during the computations. An optimal order convergence is obtained. Numerical examples are provided to show efficiency and application.展开更多
Black phosphorus （BP）, an attractive two-dimensional （2D） semiconductor, is widely used in the fields of optoelec- tronic devices, biomedicine, and chemical sensing. Silver ion （Ag＋）, a commonly used additive i...Black phosphorus （BP）, an attractive two-dimensional （2D） semiconductor, is widely used in the fields of optoelec- tronic devices, biomedicine, and chemical sensing. Silver ion （Ag＋）, a commonly used additive in food industry, can sterilize and keep food fresh. But excessive intake of Ag＋ will harm human health. Therefore, high sensitive, fast and simple Ag＋ detection method is significant. Here, a high-performance BP field effect transistor （FET） sensor is fabricated for Ag＋ detection with high sensitivity, rapid detection speed, and wide detection concentration range. The detection limit for Ag＋ is 10 l0 mol/L. Testing time for each sample by this method is 60 s. Besides, the mechanism of BP-FET sensor for Ag＋ detection is investigated systematically. The simple BP-FET sensor may inspire some relevant research and potential applications, such as providing an effective method for the actual detection of Ag＋, especially in wimessed inspections field of food.展开更多
In these days,the increasing massive data are being produced and demanded to be processed with the rapid growth of information technology.It is difficult to rely solely on the shrinking of semiconductor devices and sc...In these days,the increasing massive data are being produced and demanded to be processed with the rapid growth of information technology.It is difficult to rely solely on the shrinking of semiconductor devices and scale-up of the integrated circuits(ICs)again in the foreseeable future.Exploring new materials,new-principle semiconductor devices and new computing architectures is becoming an urgent topic in this field.Ambipolar two-dimensional(2D)semiconductors,possessing excellent electrostatic field controllability and flexibly modulated major charge carriers,offer a possibility to construct reconfigurable devices and enable the ICs with new functions,showing great potential in computing capacity,energy efficiency,time delay and cost.This review focuses on the recent significant advancements in reconfigurable electronic and optoelectronic devices of ambipolar 2D semiconductors,and demonstrates their potential approach towards ICs,like reconfigurable circuits and neuromorphic chips.It is expected to help readers understand the device design principle of ambipolar 2D semiconductors,and push forward exploring more new-principle devices and new-architecture computing circuits,and even their product applications.展开更多
Metal-tip/Pr0.7Ca0.3MnO3/Pt devices possess two types of I-V hysteresis： clockwise vs counter clockwise depending on the tip materials. The criteria for categorization of these two types of devices can be simply base...Metal-tip/Pr0.7Ca0.3MnO3/Pt devices possess two types of I-V hysteresis： clockwise vs counter clockwise depending on the tip materials. The criteria for categorization of these two types of devices can be simply based on whether the Gibbs free energy of oxidation for the metal tip is lower or higher than that of PCMO, respectively. While the clockwise hysteresis can be attributed to electric field induced oxidation/reduction, the counter clockwise hysteresis can be explained by oxygen vacancy migration in an electrical field. Alternating-current conductance spectra also reveal distinct hopping barriers between these two categories of devices at high resistive states.展开更多
Semiconductor quantum dot structure provides a promising basis for quantum information processing, within which to reveal the quantum phase and charge transport is one of the most important issues. In this paper, by m...Semiconductor quantum dot structure provides a promising basis for quantum information processing, within which to reveal the quantum phase and charge transport is one of the most important issues. In this paper, by means of the numerical renormalization group technique, we study the quantum phase transition and the charge transport for a parallel triple dot device in the strongly correlated limit, focusing on the effect of inter-dot hopping t beyond the Kondo regime. We find the quantum behaviors depend closely on the initial electron number on the dots, and the present model may map to single,double, and side-coupled impurity models in different parameter spaces. An orbital spin-1/2 Kondo effect between the conduction leads and the bonding orbital, and several magnetic-frustration phases are demonstrated when t is adjusted to different regimes. To understand these phenomena, a canonical transformation of the energy levels is given, and important physical quantities with respect to increasing t and necessary theoretical discussions are shown.展开更多
As semiconductor devices,the terahertz quantum-cascade laser is a coherent source based on intersubband transitions of unipolar carriers while the terahertz quantum-well photodetector is a kind of detector which match...As semiconductor devices,the terahertz quantum-cascade laser is a coherent source based on intersubband transitions of unipolar carriers while the terahertz quantum-well photodetector is a kind of detector which matches the laser frequency.They are solid-state,electrically operated,and can be easily integrated with other components.This paper reviews the state of the art for the design,working performance,and future directions of the two devices.Their applications in photoelectric characterization and imaging are also discussed.展开更多
Inductive energy storage systems （IES）require opening switches which are technically much more difficult to realize than closing switches. Institute of Advanced Technology （ IAT ） puts forward a meat grinder with ...Inductive energy storage systems （IES）require opening switches which are technically much more difficult to realize than closing switches. Institute of Advanced Technology （ IAT ） puts forward a meat grinder with an inductive pulse power topology called slow transfer of energy through capacitive hybrid （STRETCH）. In this topology, an integrated gate-commutated thyristor （IGCT） is capable of breaking the charging currents on the order of 4 kA, and it may encounter difficulties in expanding to higher energy systems. German-French Institute of Saint Louis （ISL） has developed a high-power opening switch based on standard high-power thyristors by using their so-called inverse current commutation with semiconductor devices （ICCOS） countercurrent commutation principle. Two topologies of the STRETCH meat grinder with ICCOS are analyzed. And they are compared based on the voltage across the main switch, the current multiplication factor and other aspects by u- sing Matlab simulations. The advantages and disadvantages of the two topologies are shown through the comparisons. Therefore a more suitable topology can be chosen for realistic applications accord- ing to their performances.展开更多
Electrically pumped high power terahertz （THz） emitters that operated above room temperature in a pulse mode were fabricated from nitrogen-doped n-type 6H-SiC. The emission spectra had peaks centered on 5 THz and 12...Electrically pumped high power terahertz （THz） emitters that operated above room temperature in a pulse mode were fabricated from nitrogen-doped n-type 6H-SiC. The emission spectra had peaks centered on 5 THz and 12 THz （20 meV and 50 meV） that were attributed to radiative transitions of excitons bound to nitrogen donor impurities. Due to the relatively deep binding energies of the nitrogen donors, above 100 meV, and the high thermal conductivity of the SiC substrates, the THz output power and operating temperature were significantly higher than previous dopant based emitters. With peak applied currents of a few amperes, and a top surface area of 1 mm2, the device emitted up to 0.5 mW at liquid nitrogen temperature （77 K）, and tens of microwatts up to 333 K. This result is the highest temperature of THz emission reported from impurity-based emitters.展开更多
The effects of channel length and width on the degradation of negative bias temperature instability （NBTI） are studied. With the channel length decreasing, the NBTI degradation increases. As tile channel edges have ...The effects of channel length and width on the degradation of negative bias temperature instability （NBTI） are studied. With the channel length decreasing, the NBTI degradation increases. As tile channel edges have more damage and latent damage for the process reasons, the device can be divided into three parts： the gate and source overlap region, the middle channel region, and the gate and drain overlap region. When the NBTI stress is applied, the non-uniform distribution of the generated defects in the three parts will be generated due to the inhomogeneous degradation. With tile decreasing channel length, tile channel edge regions will take up a larger ratio to the middle channel region and the degradation of NBTI is enhanced. The channel width also plays an important role in the degradation of NBTI. There is an inflection point during the decreasing channel width. There are two particular factors： the lower vertical electric field effect for the thicker gate oxide thickness of the sha/low trench isolation （STI） edge and the STI mechanical stress effecting on the NBTI degradation. The former reduces and the latter intensifies the degradation. Under the mutual compromise of the both factors, when the effect of the STI mechanical stress starts to prevail over the lower vertical electric field effect with the channel width decreasing, the inflection point comes into being.展开更多
We have fabricated ZnO-based thin-film transistors （TFTs） by low-cost ultrasonic spray pyrolysis. The devices exhibit high saturation mobility of about 0. 6 cm2 /Vs and on-off current ratio of 10^5. The electrical c...We have fabricated ZnO-based thin-film transistors （TFTs） by low-cost ultrasonic spray pyrolysis. The devices exhibit high saturation mobility of about 0. 6 cm2 /Vs and on-off current ratio of 10^5. The electrical characteristics of ZnO-based TFTs show that ultrasonic spray pyrolysis technique can be used as a promising approach to attain high-performance electronic devices. Furthermore, the deposition techniques make the operating process attractive for flexible electronics.展开更多
The effect of In composition on two-dimensional electron gas in wurtzite AlGaN/InGaN heterostructures is theoretically investigated. The sheet carrier density is shown to increase nearly linearly with In mole fraction...The effect of In composition on two-dimensional electron gas in wurtzite AlGaN/InGaN heterostructures is theoretically investigated. The sheet carrier density is shown to increase nearly linearly with In mole fraction x, due to the increase in the polarization charge at the AlGaN/InGaN interface. The electron sheet density is enhanced with the doping in the AlGaN layer. The sheet carrier density is as high as 3.7×1013 cm^-2 at the donor density of 10×1018 cm^-3 for the HEMT structure with x=0.3. The contribution of additional donor density on the electron sheet density is nearly independent of the In mole fraction.展开更多
Flexible vanadyl-phthalocyanine （VOPc） thin-film transistors are fabricated by the weak epitaxy growth （WEG） method. The devices show a mobility of 0.5 cm2/Vs, an on/off ratio of 105 and a low leakage current of 1...Flexible vanadyl-phthalocyanine （VOPc） thin-film transistors are fabricated by the weak epitaxy growth （WEG） method. The devices show a mobility of 0.5 cm2/Vs, an on/off ratio of 105 and a low leakage current of 10-9 A. The performances exhibit strong dependence on bending conditions and reversible change can be found when the bending strain is less than 1.5%. This results from the change of the trap density calculated by subthreshold slopes. The results indicate that VOPc films fabricated by the WEG method have good durability to flexing and possess great potential in flexible electronics.展开更多
Effects of dopant properties on microstructures and the electrical characteristics of poly （3-hexylthiophene） （P3HT） films are studied by doping 0.1 wt% 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane （F4？T...Effects of dopant properties on microstructures and the electrical characteristics of poly （3-hexylthiophene） （P3HT） films are studied by doping 0.1 wt% 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane （F4？TCNQ）, 6,6-phenyl-C61butyric acid methyl ester （PCBM） and N,N＇？Diphenyl-N,N＇-（m-tolyl）-benzidine （TPD） into P3HT, respectively. The introductions of various dopants in small quantities increase the field-effect mobility and the I on/Ioff ratio of P3HT thin-film transistors. However, each of dopants shows various effects on the crystalline order and the molecular orientation of P3HT films and the performance of P3HT thin-film transistors. These can be attributed to the various size, shape and energy-level properties of the dopants.展开更多
Characteristics of single- and multi-finger mesa InGaAs/InP double heterojunction bipolar transistors （DHBTs） are compared. The current gain decreases with the increasing number nf of the emitter fingers due to the ...Characteristics of single- and multi-finger mesa InGaAs/InP double heterojunction bipolar transistors （DHBTs） are compared. The current gain decreases with the increasing number nf of the emitter fingers due to the mutual thermal interaction between the fingers. The Kirk current can be as high as 150mA for four-finger DHBT. No degradation of the peak of the current gain cutoff frequency ft is found for multi-finger DHBTs. The peak of the maximum oscillation frequency fmax decreases with an increase of nf due to the increasing parasitic resistance of the base. The results are very helpful for applications of the common-base DHBTs in power amplifiers operating at very high frequencies.展开更多
InAs infrared-sensitive solar cells are fabricated by using the films grown by the liquid phase epitaxy technique. The film microstructures are characterized by x-ray diffraction and scanning electronic microscopy. Th...InAs infrared-sensitive solar cells are fabricated by using the films grown by the liquid phase epitaxy technique. The film microstructures are characterized by x-ray diffraction and scanning electronic microscopy. The current-voltage characteristics of the solar cells in the dark and under AM1.5 illumination at 300 K and 77 K are discussed. The conversion efficiency of p-InAs/n-sub InAs cells decreases when the thickness of the p-type film changes from 1.7 μm to 3.5 μm, which is caused by the reduced effective photons near p？n junction. The p-InAs/n-InAs/n-sub InAs solar cell with the conversion efficiency of 7.43% in 1-2.5 μm under AM1.5 at 77 K is obtained. The short circuit current density increases dramatically with decreasing temperature due to the weakened effect of phonon scattering.展开更多
We report a self-collimating demonstration in planar photonic crystals （PhCs） fabricated in silicon-on-insulator （SOI） wafers using 0.18 μm silicon complimentary metal oxide semiconductor （CMOS） techniques. The...We report a self-collimating demonstration in planar photonic crystals （PhCs） fabricated in silicon-on-insulator （SOI） wafers using 0.18 μm silicon complimentary metal oxide semiconductor （CMOS） techniques. The emphasis was on demonstrating the self-collimation effect by using the standard CMOS equipment and process development of an optical test chip using a high-volume manufacturing facility. The PhCs are designed on the 230-nm-top-Si layer using a square lattice of air holes 280 nm in diameter. The lattice constant of the PhCs is 380 nm. The experimentally obtained wavelengths for self-collimation are in excellent agreement with theory.展开更多
基金Project supported by the Special Foundation for State Major Basic Research Program of China （Grant No G2000035602） and the National Natural Science Foundation of China （Grant No 90307006）.
文摘A two-dimensional （2D） full band self-consistent ensemble Monte Carlo （MC） method for solving the quantum Boltzmann equation, including collision broadening and quantum potential corrections, is developed to extend the MC method to the study of nano-scale semiconductor devices with obvious quantum mechanical （QM） effects. The quantum effects both in real space and momentum space in nano-scale semiconductor devices can be simulated. The effective mobility in the inversion layer of n and p channel MOSFET is simulated and compared with experimental data to verify this method. With this method 50nm ultra thin body silicon on insulator MOSFET are simulated. Results indicate that this method can be used to simulate the 2D QM effects in semiconductor devices including tunnelling effect.
基金This work is supported by the Major State Basic Research Program of China (19990328), the National Tackling Key Problem Program, the National Science Foundation of China (10271066 and 0372052), and the Doctorate Foundation of the Ministry of Education of China (20030422047).
文摘Characteristic finite difference fractional step schemes are put forward. The electric potential equation is described by a seven-point finite difference scheme, and the electron and hole concentration equations are treated by a kind of characteristic finite difference fractional step methods. The temperature equation is described by a fractional step method. Thick and thin grids are made use of to form a complete set. Piecewise threefold quadratic interpolation, symmetrical extension, calculus of variations, commutativity of operator product, decomposition of high order difference operators and prior estimates are also made use of. Optimal order estimates in l2 norm are derived to determine the error of the approximate solution. The well-known problem is thorongley and completely solred.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61404098 and 61274079)the Doctoral Fund of Ministry of Education of China(Grant No.20130203120017)+2 种基金the National Key Basic Research Program of China(Grant No.2015CB759600)the National Grid Science&Technology Project,China(Grant No.SGRI-WD-71-14-018)the Key Specific Project in the National Science&Technology Program,China(Grant Nos.2013ZX02305002-002 and 2015CB759600)
文摘The effect of nitric oxide（NO） annealing on charge traps in the oxide insulator and transition layer in n-type4H–Si C metal–oxide–semiconductor（MOS） devices has been investigated using the time-dependent bias stress（TDBS）,capacitance–voltage（C–V）,and secondary ion mass spectroscopy（SIMS）.It is revealed that two main categories of charge traps,near interface oxide traps（Nniot） and oxide traps（Not）,have different responses to the TDBS and C–V characteristics in NO-annealed and Ar-annealed samples.The Nniotare mainly responsible for the hysteresis occurring in the bidirectional C–V characteristics,which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor.However,Not is mainly responsible for the TDBS induced C–V shifts.Electrons tunneling into the Not are hardly released quickly when suffering TDBS,resulting in the problem of the threshold voltage stability.Compared with the Ar-annealed sample,Nniotcan be significantly suppressed by the NO annealing,but there is little improvement of Not.SIMS results demonstrate that the Nniotare distributed within the transition layer,which correlated with the existence of the excess silicon.During the NO annealing process,the excess Si atoms incorporate into nitrogen in the transition layer,allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot.
文摘The transient behavior of a semiconductor device consists of a Poisson equation for the electric potential and of two nonlinear parabolic equations for the electron density and hole density. The electric potential equation is discretized by a mixed finite element method. The electron and hole density equations are treated by implicit-explicit multistep finite element methods. The schemes are very efficient. The optimal order error estimates both in time and space are derived.
基金supported the Natural Science Foundation of Shandong Province(ZR2016AM08)Natural Science Foundation of Hunan Province(2018JJ2028)National Natural Science Foundation of China(11871312).
文摘The numerical simulation of a three-dimensional semiconductor device is a fundamental problem in information science. The mathematical model is defined by an initialboundary nonlinear system of four partial differential equations: an elliptic equation for electric potential, two convection-diffusion equations for electron concentration and hole concentration, and a heat conduction equation for temperature. The first equation is solved by the conservative block-centered method. The concentrations and temperature are computed by the block-centered upwind difference method on a changing mesh, where the block-centered method and upwind approximation are used to discretize the diffusion and convection, respectively. The computations on a changing mesh show very well the local special properties nearby the P-N junction. The upwind scheme is applied to approximate the convection, and numerical dispersion and nonphysical oscillation are avoided. The block-centered difference computes concentrations, temperature, and their adjoint vector functions simultaneously.The local conservation of mass, an important rule in the numerical simulation of a semiconductor device, is preserved during the computations. An optimal order convergence is obtained. Numerical examples are provided to show efficiency and application.
基金Project support by the National Natural Science Foundation of China(Grant Nos.61605131 and 61435010)the Shenzhen Science and Technology Research Fund,China(Grant No.JCYJ20150324141711624)
文摘Black phosphorus （BP）, an attractive two-dimensional （2D） semiconductor, is widely used in the fields of optoelec- tronic devices, biomedicine, and chemical sensing. Silver ion （Ag＋）, a commonly used additive in food industry, can sterilize and keep food fresh. But excessive intake of Ag＋ will harm human health. Therefore, high sensitive, fast and simple Ag＋ detection method is significant. Here, a high-performance BP field effect transistor （FET） sensor is fabricated for Ag＋ detection with high sensitivity, rapid detection speed, and wide detection concentration range. The detection limit for Ag＋ is 10 l0 mol/L. Testing time for each sample by this method is 60 s. Besides, the mechanism of BP-FET sensor for Ag＋ detection is investigated systematically. The simple BP-FET sensor may inspire some relevant research and potential applications, such as providing an effective method for the actual detection of Ag＋, especially in wimessed inspections field of food.
基金Project supported by the National Natural Science Foundation of China (Grant No.62274037)the National Key Research and Development Program of China (Grant No.2018YFA0703703)+1 种基金the Ministry of Science and Technology of China (Grant No.2018YFE0118300)the State Key Laboratory of ASIC&System (Grant No.2021MS003)。
文摘In these days,the increasing massive data are being produced and demanded to be processed with the rapid growth of information technology.It is difficult to rely solely on the shrinking of semiconductor devices and scale-up of the integrated circuits(ICs)again in the foreseeable future.Exploring new materials,new-principle semiconductor devices and new computing architectures is becoming an urgent topic in this field.Ambipolar two-dimensional(2D)semiconductors,possessing excellent electrostatic field controllability and flexibly modulated major charge carriers,offer a possibility to construct reconfigurable devices and enable the ICs with new functions,showing great potential in computing capacity,energy efficiency,time delay and cost.This review focuses on the recent significant advancements in reconfigurable electronic and optoelectronic devices of ambipolar 2D semiconductors,and demonstrates their potential approach towards ICs,like reconfigurable circuits and neuromorphic chips.It is expected to help readers understand the device design principle of ambipolar 2D semiconductors,and push forward exploring more new-principle devices and new-architecture computing circuits,and even their product applications.
基金Supported by the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KJCX2-SW-W26, and the National Natural Science Foundation of China under Grant Nos 90406017 and 10427402.
文摘Metal-tip/Pr0.7Ca0.3MnO3/Pt devices possess two types of I-V hysteresis： clockwise vs counter clockwise depending on the tip materials. The criteria for categorization of these two types of devices can be simply based on whether the Gibbs free energy of oxidation for the metal tip is lower or higher than that of PCMO, respectively. While the clockwise hysteresis can be attributed to electric field induced oxidation/reduction, the counter clockwise hysteresis can be explained by oxygen vacancy migration in an electrical field. Alternating-current conductance spectra also reveal distinct hopping barriers between these two categories of devices at high resistive states.
基金Project supported by the National Natural Science Foundation of China(Grant No.11504102)the Scientific Research Items Foundation of Hubei Educational Committee(Grant Nos.Q20161803 and D20171803)the Doctoral Scientific Research Foundation of Hubei University of Automotive Technology(Grant No.BK201407)
文摘Semiconductor quantum dot structure provides a promising basis for quantum information processing, within which to reveal the quantum phase and charge transport is one of the most important issues. In this paper, by means of the numerical renormalization group technique, we study the quantum phase transition and the charge transport for a parallel triple dot device in the strongly correlated limit, focusing on the effect of inter-dot hopping t beyond the Kondo regime. We find the quantum behaviors depend closely on the initial electron number on the dots, and the present model may map to single,double, and side-coupled impurity models in different parameter spaces. An orbital spin-1/2 Kondo effect between the conduction leads and the bonding orbital, and several magnetic-frustration phases are demonstrated when t is adjusted to different regimes. To understand these phenomena, a canonical transformation of the energy levels is given, and important physical quantities with respect to increasing t and necessary theoretical discussions are shown.
基金the National Key R&D Program of China(Grant No.2017YFA0701005)the National Natural Science Foundation of China(Grant Nos.61927813,61775229,61704181,and 61991432)the Shanghai International Cooperation Project,China(Grant No.18590780100).
文摘As semiconductor devices,the terahertz quantum-cascade laser is a coherent source based on intersubband transitions of unipolar carriers while the terahertz quantum-well photodetector is a kind of detector which matches the laser frequency.They are solid-state,electrically operated,and can be easily integrated with other components.This paper reviews the state of the art for the design,working performance,and future directions of the two devices.Their applications in photoelectric characterization and imaging are also discussed.
文摘Inductive energy storage systems （IES）require opening switches which are technically much more difficult to realize than closing switches. Institute of Advanced Technology （ IAT ） puts forward a meat grinder with an inductive pulse power topology called slow transfer of energy through capacitive hybrid （STRETCH）. In this topology, an integrated gate-commutated thyristor （IGCT） is capable of breaking the charging currents on the order of 4 kA, and it may encounter difficulties in expanding to higher energy systems. German-French Institute of Saint Louis （ISL） has developed a high-power opening switch based on standard high-power thyristors by using their so-called inverse current commutation with semiconductor devices （ICCOS） countercurrent commutation principle. Two topologies of the STRETCH meat grinder with ICCOS are analyzed. And they are compared based on the voltage across the main switch, the current multiplication factor and other aspects by u- sing Matlab simulations. The advantages and disadvantages of the two topologies are shown through the comparisons. Therefore a more suitable topology can be chosen for realistic applications accord- ing to their performances.
基金supported by the NSF Award No.DMR-0601920ONR Contract No.N0001-4-00-1-0834
文摘Electrically pumped high power terahertz （THz） emitters that operated above room temperature in a pulse mode were fabricated from nitrogen-doped n-type 6H-SiC. The emission spectra had peaks centered on 5 THz and 12 THz （20 meV and 50 meV） that were attributed to radiative transitions of excitons bound to nitrogen donor impurities. Due to the relatively deep binding energies of the nitrogen donors, above 100 meV, and the high thermal conductivity of the SiC substrates, the THz output power and operating temperature were significantly higher than previous dopant based emitters. With peak applied currents of a few amperes, and a top surface area of 1 mm2, the device emitted up to 0.5 mW at liquid nitrogen temperature （77 K）, and tens of microwatts up to 333 K. This result is the highest temperature of THz emission reported from impurity-based emitters.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60890191 and 60736033, the National Key Science and Technology Special Project under Grant No 2008ZX01002-002, and the National Key Technology R ＆ D Program under Grant No 2007BAK25B03.
文摘The effects of channel length and width on the degradation of negative bias temperature instability （NBTI） are studied. With the channel length decreasing, the NBTI degradation increases. As tile channel edges have more damage and latent damage for the process reasons, the device can be divided into three parts： the gate and source overlap region, the middle channel region, and the gate and drain overlap region. When the NBTI stress is applied, the non-uniform distribution of the generated defects in the three parts will be generated due to the inhomogeneous degradation. With tile decreasing channel length, tile channel edge regions will take up a larger ratio to the middle channel region and the degradation of NBTI is enhanced. The channel width also plays an important role in the degradation of NBTI. There is an inflection point during the decreasing channel width. There are two particular factors： the lower vertical electric field effect for the thicker gate oxide thickness of the sha/low trench isolation （STI） edge and the STI mechanical stress effecting on the NBTI degradation. The former reduces and the latter intensifies the degradation. Under the mutual compromise of the both factors, when the effect of the STI mechanical stress starts to prevail over the lower vertical electric field effect with the channel width decreasing, the inflection point comes into being.
基金Support from the National Basic Research Program of China under Grant No 2009CB930600, the National Natural Science Foundation of China under Grant Nos 20704023, 60876010, 60706017 and 20774043, the Key Project of the Ministry of Education of China （Nos 208050, 707032, NCET-07-0446）, the Natural Science Foundation of Jiangsu Province （No 07KJB150082, BK2008053, 08KJB510013, SJ209003 and TJ207035）, the Research Fund for Postgraduate Innovation Project of Jiangsu Province （CX08B_083Z） and STTTP （No 2009120）.
文摘We have fabricated ZnO-based thin-film transistors （TFTs） by low-cost ultrasonic spray pyrolysis. The devices exhibit high saturation mobility of about 0. 6 cm2 /Vs and on-off current ratio of 10^5. The electrical characteristics of ZnO-based TFTs show that ultrasonic spray pyrolysis technique can be used as a promising approach to attain high-performance electronic devices. Furthermore, the deposition techniques make the operating process attractive for flexible electronics.
文摘The effect of In composition on two-dimensional electron gas in wurtzite AlGaN/InGaN heterostructures is theoretically investigated. The sheet carrier density is shown to increase nearly linearly with In mole fraction x, due to the increase in the polarization charge at the AlGaN/InGaN interface. The electron sheet density is enhanced with the doping in the AlGaN layer. The sheet carrier density is as high as 3.7×1013 cm^-2 at the donor density of 10×1018 cm^-3 for the HEMT structure with x=0.3. The contribution of additional donor density on the electron sheet density is nearly independent of the In mole fraction.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50773079, 50803063 and 20621401, and the National Basic Research Program of China under Grant No 2009CB939702.
文摘Flexible vanadyl-phthalocyanine （VOPc） thin-film transistors are fabricated by the weak epitaxy growth （WEG） method. The devices show a mobility of 0.5 cm2/Vs, an on/off ratio of 105 and a low leakage current of 10-9 A. The performances exhibit strong dependence on bending conditions and reversible change can be found when the bending strain is less than 1.5%. This results from the change of the trap density calculated by subthreshold slopes. The results indicate that VOPc films fabricated by the WEG method have good durability to flexing and possess great potential in flexible electronics.
文摘Effects of dopant properties on microstructures and the electrical characteristics of poly （3-hexylthiophene） （P3HT） films are studied by doping 0.1 wt% 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane （F4？TCNQ）, 6,6-phenyl-C61butyric acid methyl ester （PCBM） and N,N＇？Diphenyl-N,N＇-（m-tolyl）-benzidine （TPD） into P3HT, respectively. The introductions of various dopants in small quantities increase the field-effect mobility and the I on/Ioff ratio of P3HT thin-film transistors. However, each of dopants shows various effects on the crystalline order and the molecular orientation of P3HT films and the performance of P3HT thin-film transistors. These can be attributed to the various size, shape and energy-level properties of the dopants.
文摘Characteristics of single- and multi-finger mesa InGaAs/InP double heterojunction bipolar transistors （DHBTs） are compared. The current gain decreases with the increasing number nf of the emitter fingers due to the mutual thermal interaction between the fingers. The Kirk current can be as high as 150mA for four-finger DHBT. No degradation of the peak of the current gain cutoff frequency ft is found for multi-finger DHBTs. The peak of the maximum oscillation frequency fmax decreases with an increase of nf due to the increasing parasitic resistance of the base. The results are very helpful for applications of the common-base DHBTs in power amplifiers operating at very high frequencies.
基金Supported by the National Basic Research Program of China under Grant No 2010CB933700, the National Natural Science Foundation of China under Grant Nos 10804117 and 60221502, the Natural Science Foundation of Shanghai under Grant No 08ZR1421900, and the Knowledge Innovation Project in Chinese Academy of Sciences.
文摘InAs infrared-sensitive solar cells are fabricated by using the films grown by the liquid phase epitaxy technique. The film microstructures are characterized by x-ray diffraction and scanning electronic microscopy. The current-voltage characteristics of the solar cells in the dark and under AM1.5 illumination at 300 K and 77 K are discussed. The conversion efficiency of p-InAs/n-sub InAs cells decreases when the thickness of the p-type film changes from 1.7 μm to 3.5 μm, which is caused by the reduced effective photons near p？n junction. The p-InAs/n-InAs/n-sub InAs solar cell with the conversion efficiency of 7.43% in 1-2.5 μm under AM1.5 at 77 K is obtained. The short circuit current density increases dramatically with decreasing temperature due to the weakened effect of phonon scattering.
基金Supported by the National Natural Science Foundation of China under Grant No 60721004, and the Shanghai Institute of Microsystern and Information Technology Fund for Young Scholars.
文摘We report a self-collimating demonstration in planar photonic crystals （PhCs） fabricated in silicon-on-insulator （SOI） wafers using 0.18 μm silicon complimentary metal oxide semiconductor （CMOS） techniques. The emphasis was on demonstrating the self-collimation effect by using the standard CMOS equipment and process development of an optical test chip using a high-volume manufacturing facility. The PhCs are designed on the 230-nm-top-Si layer using a square lattice of air holes 280 nm in diameter. The lattice constant of the PhCs is 380 nm. The experimentally obtained wavelengths for self-collimation are in excellent agreement with theory.
