Trap-assisted tunneling（TAT） has attracted more and more attention, because it seriously affects the sub-threshold characteristic of tunnel field-effect transistor（TFET）. In this paper, we assess subthreshold perf...Trap-assisted tunneling（TAT） has attracted more and more attention, because it seriously affects the sub-threshold characteristic of tunnel field-effect transistor（TFET）. In this paper, we assess subthreshold performance of double gate TFET（DG-TFET） through a band-to-band tunneling（BTBT） model, including phonon-assisted scattering and acoustic surface phonons scattering. Interface state density profile（D_（it）） and the trap level are included in the simulation to analyze their effects on TAT current and the mechanism of gate leakage current.展开更多
Trap-assisted charge recombination is one of the primary limitationsof restricting the performance of organic solar cells. However, effectivelyreducing the presence of traps in the photoactive layer remains challengin...Trap-assisted charge recombination is one of the primary limitationsof restricting the performance of organic solar cells. However, effectivelyreducing the presence of traps in the photoactive layer remains challenging.Herein, wide bandgap polymer donor PTzBI-dF is demonstrated as an effectivemodulator for enhancing the crystallinity of the bulk heterojunction active layerscomposed of D18 derivatives blended with Y6, leading to dense and orderedmolecular packings, and thus, improves photoluminescence quenching properties.As a result, the photovoltaic devices exhibit reduced trap-assisted charge recombinationlosses, achieving an optimized power conversion efficiency of over 19%.Besides the efficiency enhancement, the devices comprised of PTzBI-dF as athird component simultaneously attain decreased current leakage, improved chargecarrier mobilities, and suppressed bimolecular charge recombination, leading toreduced energy losses. The advanced crystalline structures induced by PTzBI-dFand its characteristics, such as well-aligned energy level, and complementaryabsorption spectra, are ascribed to the promising performance improvements.Our findings suggest that donor phase engineering is a feasible approach to tuning the molecular packings in the active layer, providingguidelines for designing effective morphology modulators for high-performance organic solar cells.展开更多
Semiconductor-cocatalyst interfacial electron transfer has widely been considered as a fast step occurring on picosecond-microsecond timescale in photocatalytic reaction.However,the formed potential barriers severely ...Semiconductor-cocatalyst interfacial electron transfer has widely been considered as a fast step occurring on picosecond-microsecond timescale in photocatalytic reaction.However,the formed potential barriers severely slow this interfacial electronic process by thermionic emission.Although trap-assisted charge recombination can transfer electrons from semiconductor to cocatalyst and can even be evident under weak illumination,the parallel connection with thermionic emission makes the photocatalytic photon utilization encounter a minimum along the variation of light intensity.By this cognition,the light-intensity-dependent photocatalytic behaviors can be predicted by simulating the photoinduced semiconductor-cocatalyst interfacial electron transfer that mainly determines the reaction rate.We then propose a(photo)electrochemical method to evaluate the time constants for occurring this interfacial electronic process in actual photocatalytic reaction without relying on extremely high photon flux that is required to generate discernible optical signal in common instrumental methods based on ultrafast pulse laser.The evaluated decisecond-second timescale can accurately guide us to develop certain strategies to facilitate this rate-determining step to improve photon utilization.展开更多
This study investigates the gate leakage mechanisms of AlN/GaN metal–insulator–semiconductor high-electronmobility transistors(MIS-HEMTs)fabricated on silicon substrate with Al_(2)O_(3)/SiN as stacked gate dielectri...This study investigates the gate leakage mechanisms of AlN/GaN metal–insulator–semiconductor high-electronmobility transistors(MIS-HEMTs)fabricated on silicon substrate with Al_(2)O_(3)/SiN as stacked gate dielectrics,analyzing behaviors across high and low temperature conditions.In the high-temperature reverse bias region(T>275 K,V_(G)<0 V),Poole–Frenkel emission(PFE)dominates at low electric fields,while trap-assisted tunneling(TAT)is the primary mechanism at medium to high electric fields.The shift from PFE to TAT as the dominant conduction mechanism is due to the increased tunneling effect of electrons as the electric field strength rises.Additionally,TAT is found to be the main gate leakage mechanism under low-temperature reverse bias(T<275 K,V_(G)<0 V).At lower temperatures,the reduction in electron energy causes the emission process to rely more on electric field forces.Furthermore,under forward bias conditions at both high and low temperatures(225 K<T<375 K,V_(G)>0 V),conduction is primarily dominated by defect-assisted tunneling(DAT).展开更多
The demand for lightweight, flexible, and high-performance portable power sources urgently requires high-efficiency and stable flexible solar cells. In the case of perovskite solar cells(PSCs), most of the common elec...The demand for lightweight, flexible, and high-performance portable power sources urgently requires high-efficiency and stable flexible solar cells. In the case of perovskite solar cells(PSCs), most of the common electron transport layer(ETL) needs to be annealed for improving the optoelectronic properties,while conventional flexible substrates could barely stand the high temperature. Herein, a vacuumassisted annealing SnO_(2) ETL at low temperature(100℃) is utilized in flexible PSCs and achieved high efficiency of 20.14%. Meanwhile, the open-circuit voltage(V_(oc)) increases from 1.07 V to 1.14 V. The flexible PSCs also show robust bending stability with 86.8% of the initial efficiency is retained after 1000 bending cycles at a bending radius of 5 mm. X-ray photoelectron spectroscopy(XPS), atomic force microscopy(AFM), and contact angle measurements show that the density of oxygen vacancies, the surface roughness of the SnO_(2) layer, and film hydrophobicity are significantly increased, respectively. These improvements could be due to the oxygen-deficient environment in a vacuum chamber, and the rapid evaporation of solvents. The proposed vacuum-assisted low-temperature annealing method not only improves the efficiency of flexible PSCs but is also compatible and promising in the large-scale commercialization of flexible PSCs.展开更多
The conduction mechanism of stress induced leakage current （SILC） through 2nm gate oxide is studied over a gate voltage range between 1.7V and stress voltage under constant voltage stress （CVS）. The simulation res...The conduction mechanism of stress induced leakage current （SILC） through 2nm gate oxide is studied over a gate voltage range between 1.7V and stress voltage under constant voltage stress （CVS）. The simulation results show that the SILC is formed by trap-assisted tunnelling （TAT） process which is dominated by oxide traps induced by high field stresses. Their energy levels obtained by this work are approximately 1.9eV from the oxide conduction band, and the traps are believed to be the oxygen-related donor-like defects induced by high field stresses. The dependence of the trap density on stress time and oxide electric field is also investigated.展开更多
The effects of gate oxide traps on gate leakage current and device performance of metal–oxide–nitride–oxide–silicon(MONOS)-structured NAND flash memory are investigated through Sentaurus TCAD. The trap-assisted tu...The effects of gate oxide traps on gate leakage current and device performance of metal–oxide–nitride–oxide–silicon(MONOS)-structured NAND flash memory are investigated through Sentaurus TCAD. The trap-assisted tunneling(TAT)model is implemented to simulate the leakage current of MONOS-structured memory cell. In this study, trap position, trap density, and trap energy are systematically analyzed for ascertaining their influences on gate leakage current, program/erase speed, and data retention properties. The results show that the traps in blocking layer significantly enhance the gate leakage current and also facilitates the cell program/erase. Trap density ~10^(18) cm^(-3) and trap energy ~ 1 eV in blocking layer can considerably improve cell program/erase speed without deteriorating data retention. The result conduces to understanding the role of gate oxide traps in cell degradation of MONOS-structured NAND flash memory.展开更多
The reverse gate leakage mechanism of W-gate and Ti N-gate AlGaN/GaN high-electron-mobility transistors(HEMTs)with N2plasma surface treatment is investigated using current–voltage(I–V)and capacitance–voltage(C–V)c...The reverse gate leakage mechanism of W-gate and Ti N-gate AlGaN/GaN high-electron-mobility transistors(HEMTs)with N2plasma surface treatment is investigated using current–voltage(I–V)and capacitance–voltage(C–V)characteristics and theoretical calculation analysis.It is found that the main reverse gate leakage mechanism of both devices is the trapassisted tunneling(TAT)mechanism in the entire reverse bias region(-30 V to 0 V).It is also found that the reverse gate leakage current of the W-gate Al GaN/GaN HEMTs is smaller than that of the TiN gate at high reverse gate bias voltage.Moreover,the activation energies of the extracted W-gate and Ti N-gate AlGaN/GaN HEMTs are 0.0551 e V–0.127 eV and0.112 eV–0.201 eV,respectively.展开更多
Solution-processed fluorescent organic light-emitting diodes(OLEDs)are believed to be favorable for low-cost,large-area,and flexible displays but still suffer from the limited external quantum efficiency(EQE)below 5%....Solution-processed fluorescent organic light-emitting diodes(OLEDs)are believed to be favorable for low-cost,large-area,and flexible displays but still suffer from the limited external quantum efficiency(EQE)below 5%.Herein,we demonstrate the EQE breakthrough by introducing a donor–acceptor type thermally activated delayed fluorescence(TADF)polymer as the sensitizer for the typical green-emitting fluorescent dopants.Benefitting from their matched energy alignment,the unwanted trap-assisted recombination directly on fluorescent dopant is prevented to avoid the additional loss of triplet excitons.Indeed,triplet excitons are mainly formed on the polymeric TADF sensitizer via a Langevin recombination and then spin-flipped to singlet excitons due to the good upconversion capability.Followed by an efficient Förster energy transfer,both singlet and triplet excitons can be harvested by fluorescent dopants,leading to a promising solution-processed green hyperfluorescence with a record-high EQE of 21.2%(72.2cd/A,59.7lm/W)and Commission Internationale de L'Eclairage coordinates of(0.32,0.59).The results clearly highlight the great potential of solution-processed fluorescent OLEDs based on TADF polymers as the sensitizer.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61574109 and 61204092)
文摘Trap-assisted tunneling（TAT） has attracted more and more attention, because it seriously affects the sub-threshold characteristic of tunnel field-effect transistor（TFET）. In this paper, we assess subthreshold performance of double gate TFET（DG-TFET） through a band-to-band tunneling（BTBT） model, including phonon-assisted scattering and acoustic surface phonons scattering. Interface state density profile（D_（it）） and the trap level are included in the simulation to analyze their effects on TAT current and the mechanism of gate leakage current.
基金support from the National Natural Science Foundation of China(62275057)the Guangxi Natural Science Foundation(2023GXNSFFA026004 and 2022GXNSFDA035066)+2 种基金the Innovation Project of Guangxi Graduate Education(YCBZ2024034)Natural Science Foundation of Ningbo under grant(2022J149)Natural Science Foundation of Ningbo under grant(2022A-230-G)
文摘Trap-assisted charge recombination is one of the primary limitationsof restricting the performance of organic solar cells. However, effectivelyreducing the presence of traps in the photoactive layer remains challenging.Herein, wide bandgap polymer donor PTzBI-dF is demonstrated as an effectivemodulator for enhancing the crystallinity of the bulk heterojunction active layerscomposed of D18 derivatives blended with Y6, leading to dense and orderedmolecular packings, and thus, improves photoluminescence quenching properties.As a result, the photovoltaic devices exhibit reduced trap-assisted charge recombinationlosses, achieving an optimized power conversion efficiency of over 19%.Besides the efficiency enhancement, the devices comprised of PTzBI-dF as athird component simultaneously attain decreased current leakage, improved chargecarrier mobilities, and suppressed bimolecular charge recombination, leading toreduced energy losses. The advanced crystalline structures induced by PTzBI-dFand its characteristics, such as well-aligned energy level, and complementaryabsorption spectra, are ascribed to the promising performance improvements.Our findings suggest that donor phase engineering is a feasible approach to tuning the molecular packings in the active layer, providingguidelines for designing effective morphology modulators for high-performance organic solar cells.
文摘Semiconductor-cocatalyst interfacial electron transfer has widely been considered as a fast step occurring on picosecond-microsecond timescale in photocatalytic reaction.However,the formed potential barriers severely slow this interfacial electronic process by thermionic emission.Although trap-assisted charge recombination can transfer electrons from semiconductor to cocatalyst and can even be evident under weak illumination,the parallel connection with thermionic emission makes the photocatalytic photon utilization encounter a minimum along the variation of light intensity.By this cognition,the light-intensity-dependent photocatalytic behaviors can be predicted by simulating the photoinduced semiconductor-cocatalyst interfacial electron transfer that mainly determines the reaction rate.We then propose a(photo)electrochemical method to evaluate the time constants for occurring this interfacial electronic process in actual photocatalytic reaction without relying on extremely high photon flux that is required to generate discernible optical signal in common instrumental methods based on ultrafast pulse laser.The evaluated decisecond-second timescale can accurately guide us to develop certain strategies to facilitate this rate-determining step to improve photon utilization.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62188102,62174125,and 62131014).
文摘This study investigates the gate leakage mechanisms of AlN/GaN metal–insulator–semiconductor high-electronmobility transistors(MIS-HEMTs)fabricated on silicon substrate with Al_(2)O_(3)/SiN as stacked gate dielectrics,analyzing behaviors across high and low temperature conditions.In the high-temperature reverse bias region(T>275 K,V_(G)<0 V),Poole–Frenkel emission(PFE)dominates at low electric fields,while trap-assisted tunneling(TAT)is the primary mechanism at medium to high electric fields.The shift from PFE to TAT as the dominant conduction mechanism is due to the increased tunneling effect of electrons as the electric field strength rises.Additionally,TAT is found to be the main gate leakage mechanism under low-temperature reverse bias(T<275 K,V_(G)<0 V).At lower temperatures,the reduction in electron energy causes the emission process to rely more on electric field forces.Furthermore,under forward bias conditions at both high and low temperatures(225 K<T<375 K,V_(G)>0 V),conduction is primarily dominated by defect-assisted tunneling(DAT).
基金supported by the National Natural Science Foundation of China(61774046)。
文摘The demand for lightweight, flexible, and high-performance portable power sources urgently requires high-efficiency and stable flexible solar cells. In the case of perovskite solar cells(PSCs), most of the common electron transport layer(ETL) needs to be annealed for improving the optoelectronic properties,while conventional flexible substrates could barely stand the high temperature. Herein, a vacuumassisted annealing SnO_(2) ETL at low temperature(100℃) is utilized in flexible PSCs and achieved high efficiency of 20.14%. Meanwhile, the open-circuit voltage(V_(oc)) increases from 1.07 V to 1.14 V. The flexible PSCs also show robust bending stability with 86.8% of the initial efficiency is retained after 1000 bending cycles at a bending radius of 5 mm. X-ray photoelectron spectroscopy(XPS), atomic force microscopy(AFM), and contact angle measurements show that the density of oxygen vacancies, the surface roughness of the SnO_(2) layer, and film hydrophobicity are significantly increased, respectively. These improvements could be due to the oxygen-deficient environment in a vacuum chamber, and the rapid evaporation of solvents. The proposed vacuum-assisted low-temperature annealing method not only improves the efficiency of flexible PSCs but is also compatible and promising in the large-scale commercialization of flexible PSCs.
文摘The conduction mechanism of stress induced leakage current （SILC） through 2nm gate oxide is studied over a gate voltage range between 1.7V and stress voltage under constant voltage stress （CVS）. The simulation results show that the SILC is formed by trap-assisted tunnelling （TAT） process which is dominated by oxide traps induced by high field stresses. Their energy levels obtained by this work are approximately 1.9eV from the oxide conduction band, and the traps are believed to be the oxygen-related donor-like defects induced by high field stresses. The dependence of the trap density on stress time and oxide electric field is also investigated.
基金Project supported by the San Disk Info Tech Shanghai,Chinathe Institute of Microelectronic Materials&Technology,School of Materials Science and Engineering,Shanghai Jiao Tong University,China。
文摘The effects of gate oxide traps on gate leakage current and device performance of metal–oxide–nitride–oxide–silicon(MONOS)-structured NAND flash memory are investigated through Sentaurus TCAD. The trap-assisted tunneling(TAT)model is implemented to simulate the leakage current of MONOS-structured memory cell. In this study, trap position, trap density, and trap energy are systematically analyzed for ascertaining their influences on gate leakage current, program/erase speed, and data retention properties. The results show that the traps in blocking layer significantly enhance the gate leakage current and also facilitates the cell program/erase. Trap density ~10^(18) cm^(-3) and trap energy ~ 1 eV in blocking layer can considerably improve cell program/erase speed without deteriorating data retention. The result conduces to understanding the role of gate oxide traps in cell degradation of MONOS-structured NAND flash memory.
文摘The reverse gate leakage mechanism of W-gate and Ti N-gate AlGaN/GaN high-electron-mobility transistors(HEMTs)with N2plasma surface treatment is investigated using current–voltage(I–V)and capacitance–voltage(C–V)characteristics and theoretical calculation analysis.It is found that the main reverse gate leakage mechanism of both devices is the trapassisted tunneling(TAT)mechanism in the entire reverse bias region(-30 V to 0 V).It is also found that the reverse gate leakage current of the W-gate Al GaN/GaN HEMTs is smaller than that of the TiN gate at high reverse gate bias voltage.Moreover,the activation energies of the extracted W-gate and Ti N-gate AlGaN/GaN HEMTs are 0.0551 e V–0.127 eV and0.112 eV–0.201 eV,respectively.
基金National Natural Science Foundation of China,Grant/Award Numbers:52273198,52173186,21961160720Yunnan Fundamental Research Projects,Grant/Award Numbers:202301BF070001-008,K264202230134+2 种基金The Yunling Scholar Project of“Yunnan Revitalization Talent Support Program”Natural Science Foundation of Jilin Province,Grant/Award Number:20230101358JCYouth Innovation Promotion Association。
文摘Solution-processed fluorescent organic light-emitting diodes(OLEDs)are believed to be favorable for low-cost,large-area,and flexible displays but still suffer from the limited external quantum efficiency(EQE)below 5%.Herein,we demonstrate the EQE breakthrough by introducing a donor–acceptor type thermally activated delayed fluorescence(TADF)polymer as the sensitizer for the typical green-emitting fluorescent dopants.Benefitting from their matched energy alignment,the unwanted trap-assisted recombination directly on fluorescent dopant is prevented to avoid the additional loss of triplet excitons.Indeed,triplet excitons are mainly formed on the polymeric TADF sensitizer via a Langevin recombination and then spin-flipped to singlet excitons due to the good upconversion capability.Followed by an efficient Förster energy transfer,both singlet and triplet excitons can be harvested by fluorescent dopants,leading to a promising solution-processed green hyperfluorescence with a record-high EQE of 21.2%(72.2cd/A,59.7lm/W)and Commission Internationale de L'Eclairage coordinates of(0.32,0.59).The results clearly highlight the great potential of solution-processed fluorescent OLEDs based on TADF polymers as the sensitizer.
