Emission and capture characteristics of a deep hole trap(H1)in n-GaN Schottky barrier diodes(SBDs)have been investigated by optical deep level transient spectroscopy(ODLTS).Activation energy(Eemi)and capture cross-sec...Emission and capture characteristics of a deep hole trap(H1)in n-GaN Schottky barrier diodes(SBDs)have been investigated by optical deep level transient spectroscopy(ODLTS).Activation energy(Eemi)and capture cross-section(σ_(p))of H1 are determined to be 0.75 eV and 4.67×10^(−15)cm^(2),respectively.Distribution of apparent trap concentration in space charge region is demonstrated.Temperature-enhanced emission process is revealed by decrease of emission time constant.Electricfield-boosted trap emission kinetics are analyzed by the Poole−Frenkel emission(PFE)model.In addition,H1 shows point defect capture properties and temperature-enhanced capture kinetics.Taking both hole capture and emission processes into account during laser beam incidence,H1 features a trap concentration of 2.67×10^(15)cm^(−3).The method and obtained results may facilitate understanding of minority carrier trap properties in wide bandgap semiconductor material and can be applied for device reliability assessment.展开更多
Kelvin probe force microscopy(KPFM) could identify the local work function of surface at nanoscale with high-resolution on the basis of simultaneous visualization of surface topography, which provides a unique route t...Kelvin probe force microscopy(KPFM) could identify the local work function of surface at nanoscale with high-resolution on the basis of simultaneous visualization of surface topography, which provides a unique route to in-situ study of the surface information like the composition and electronic states. Currently, as a non-destructive detection protocol, KPFM demonstrates the unique potential to probe the basic nature of perovskite materials that is extremely sensitive to water, oxygen and electron beam irradiation. This paper systematically introduces the fundamentals and working mode of KPFM, and elaborates the promising applications in perovskite solar cells for energy band structures and carrier transport dynamics, trap states, crystal phases, as well as ion migration explorations. The comprehensive understanding of such potential detection engineering may provide novel and effective approaches for unraveling the unique properties of perovskite solar cells.展开更多
The emerging wide bandgap semiconductorβ-Ga_(2)O_(3) has attracted great interest due to its promising applications for high-power electronic devices and solar-blind ultraviolet photodetectors.Deep-level defects inβ...The emerging wide bandgap semiconductorβ-Ga_(2)O_(3) has attracted great interest due to its promising applications for high-power electronic devices and solar-blind ultraviolet photodetectors.Deep-level defects inβ-Ga_(2)O_(3) have been intensively studied towards improving device performance.Deep-level signatures E_(1),E_(2),and E_(3) with energy positions of 0.55–0.63,0.74–0.81,and 1.01–1.10 eV below the conduction band minimum have frequently been observed and extensively investigated,but their atomic origins are still under debate.In this work,we attempt to clarify these deep-level signatures from the comparison of theoretically predicted electron capture cross-sections of suggested candidates,Ti and Fe substituting Ga on a tetrahedral site(Ti_(GaI) and Fe_(GaI))and an octahedral site(Ti_(GaII) and Fe_(GaII)),to experimentally measured results.The first-principles approach predicted electron capture cross-sections of Ti_(GaI) and Ti_(GaII) defects are 8.56×10^(–14) and 2.97×10^(–13) cm^(2),in good agreement with the experimental values of E_(1) and E_(3) centers,respectively.We,therefore,confirmed that E_(1) and E_(3) centers are indeed associated with Ti_(GaI) and Ti_(GaII) defects,respectively.Whereas the predicted electron capture cross-sections of Fe_(Ga) defect are two orders of magnitude larger than the experimental value of the E_(2),indicating E_(2) may have other origins like C_(Ga) and Ga_(i),rather than common believed Fe_(Ga).展开更多
Carrier lifetime is one of the most fundamental physical parameters that characterizes the average time of carrier recombination in any material.The control of carrier lifetime is the key to optimizing the device func...Carrier lifetime is one of the most fundamental physical parameters that characterizes the average time of carrier recombination in any material.The control of carrier lifetime is the key to optimizing the device function by tuning the electro-optical conversion quantum yield,carrier diffusion length,carrier collection process,etc.Till now,the prevailing modulation methods are mainly by defect engineering and temperature control,which have limitations in the modulation direction and amplitude of the carrier lifetime.Here,we report an effective modulation on the ultrafast dynamics of photoexcited carriers in two-dimensional(2D)MoS2 monolayer by uniaxial tensile strain.The combination of optical ultrafast pump-probe technique and time-resolved photoluminescence(PL)spectroscopy reveals that the carrier dynamics through Auger scattering,carrier-phonon scattering,and radiative recombination keep immune to the strain.But strikingly,the uniaxial tensile strain weakens the trapping of photoexcited carriers by defects and therefore prolongs the corresponding carrier lifetime up to 440%per percent applied strain.Our results open a new avenue to enlarge the carrier lifetime of 2D MoS2,which will facilitate its applications in high-efficient optoelectronic and photovoltaic devices.展开更多
Interface traps generated under hot carrier (HC) stress in LDD nMOST's are monitored by the direct current current voltage (DCIV) measurement technique and charge pumping (CP) technique.The measured and analyzed...Interface traps generated under hot carrier (HC) stress in LDD nMOST's are monitored by the direct current current voltage (DCIV) measurement technique and charge pumping (CP) technique.The measured and analyzed results show that the D peak in DCIV spectrum,which related to the drain region,is affected by a superfluous drain leakage current.The band trap band tunneling current is dominant of this current.展开更多
基金supported by ShanghaiTech University Startup Fund 2017F0203-000-14the National Natural Science Foundation of China(Grant No.52131303)+1 种基金Natural Science Foundation of Shanghai(Grant No.22ZR1442300)in part by CAS Strategic Science and Technology Program(Grant No.XDA18000000).
文摘Emission and capture characteristics of a deep hole trap(H1)in n-GaN Schottky barrier diodes(SBDs)have been investigated by optical deep level transient spectroscopy(ODLTS).Activation energy(Eemi)and capture cross-section(σ_(p))of H1 are determined to be 0.75 eV and 4.67×10^(−15)cm^(2),respectively.Distribution of apparent trap concentration in space charge region is demonstrated.Temperature-enhanced emission process is revealed by decrease of emission time constant.Electricfield-boosted trap emission kinetics are analyzed by the Poole−Frenkel emission(PFE)model.In addition,H1 shows point defect capture properties and temperature-enhanced capture kinetics.Taking both hole capture and emission processes into account during laser beam incidence,H1 features a trap concentration of 2.67×10^(15)cm^(−3).The method and obtained results may facilitate understanding of minority carrier trap properties in wide bandgap semiconductor material and can be applied for device reliability assessment.
基金supported by the National Key Research and Development Program of China (2016YFA0202701)the Overseas Expertise Introduction Projects for Discipline Innovation (111 project, B14003)+4 种基金the National Natural Science Foundation of China (51527802, 51232001, 51702014 and 51372020)the National Major Research Program of China (2013CB932602)Beijing Municipal Science & Technology Commission (Z161100002116027)the State Key Laboratory for Advanced Metals and Materialsthe Fundamental Research Funds for the Central Universities (FRF-TP-18-042A1)
文摘Kelvin probe force microscopy(KPFM) could identify the local work function of surface at nanoscale with high-resolution on the basis of simultaneous visualization of surface topography, which provides a unique route to in-situ study of the surface information like the composition and electronic states. Currently, as a non-destructive detection protocol, KPFM demonstrates the unique potential to probe the basic nature of perovskite materials that is extremely sensitive to water, oxygen and electron beam irradiation. This paper systematically introduces the fundamentals and working mode of KPFM, and elaborates the promising applications in perovskite solar cells for energy band structures and carrier transport dynamics, trap states, crystal phases, as well as ion migration explorations. The comprehensive understanding of such potential detection engineering may provide novel and effective approaches for unraveling the unique properties of perovskite solar cells.
基金This work was supported by the National Key Research and Development Program of China under Grant No.2018YFB2200105the Key Research Program of Frontier Sciences,CAS under Grant No.ZDBS-LY-JSC019the National Natural Science Foundation of China(NSFC)under Grant Nos.11925407 and 61927901.
文摘The emerging wide bandgap semiconductorβ-Ga_(2)O_(3) has attracted great interest due to its promising applications for high-power electronic devices and solar-blind ultraviolet photodetectors.Deep-level defects inβ-Ga_(2)O_(3) have been intensively studied towards improving device performance.Deep-level signatures E_(1),E_(2),and E_(3) with energy positions of 0.55–0.63,0.74–0.81,and 1.01–1.10 eV below the conduction band minimum have frequently been observed and extensively investigated,but their atomic origins are still under debate.In this work,we attempt to clarify these deep-level signatures from the comparison of theoretically predicted electron capture cross-sections of suggested candidates,Ti and Fe substituting Ga on a tetrahedral site(Ti_(GaI) and Fe_(GaI))and an octahedral site(Ti_(GaII) and Fe_(GaII)),to experimentally measured results.The first-principles approach predicted electron capture cross-sections of Ti_(GaI) and Ti_(GaII) defects are 8.56×10^(–14) and 2.97×10^(–13) cm^(2),in good agreement with the experimental values of E_(1) and E_(3) centers,respectively.We,therefore,confirmed that E_(1) and E_(3) centers are indeed associated with Ti_(GaI) and Ti_(GaII) defects,respectively.Whereas the predicted electron capture cross-sections of Fe_(Ga) defect are two orders of magnitude larger than the experimental value of the E_(2),indicating E_(2) may have other origins like C_(Ga) and Ga_(i),rather than common believed Fe_(Ga).
基金Project supported by the Natural Science Foundation of Beijing,China(Grant No.JQ19004)the Excellent Talents Training Support Fund of Beijing,China(Grant No.2017000026833ZK11)+7 种基金the National Natural Science Foundation of China(Grant Nos.51991340 and 51991342)the National Key Research and Development Program of China(Grant Nos.2016YFA0300903 and 2016YFA0300804)the Key Research and Development Program of Guangdong Province,China(Grant Nos.2019B010931001,2020B010189001,2018B010109009,and 2018B030327001)the Science Fund from the Municipal Science&Technology Commission of Beijing,China(Grant No.Z191100007219005)the Graphene Innovation Program of Beijing,China(Grant No.Z181100004818003)the Fund from the Bureau of Industry and Information Technology of Shenzhen City,China(Graphene platform 201901161512)the Innovative and Entrepreneurial Research Team Program of Guangdong Province,China(Grant No.2016ZT06D348)the Fund from the Science,Technology,and Innovation Commission of Shenzhen Municipality,China(Grant No.KYTDPT20181011104202253).
文摘Carrier lifetime is one of the most fundamental physical parameters that characterizes the average time of carrier recombination in any material.The control of carrier lifetime is the key to optimizing the device function by tuning the electro-optical conversion quantum yield,carrier diffusion length,carrier collection process,etc.Till now,the prevailing modulation methods are mainly by defect engineering and temperature control,which have limitations in the modulation direction and amplitude of the carrier lifetime.Here,we report an effective modulation on the ultrafast dynamics of photoexcited carriers in two-dimensional(2D)MoS2 monolayer by uniaxial tensile strain.The combination of optical ultrafast pump-probe technique and time-resolved photoluminescence(PL)spectroscopy reveals that the carrier dynamics through Auger scattering,carrier-phonon scattering,and radiative recombination keep immune to the strain.But strikingly,the uniaxial tensile strain weakens the trapping of photoexcited carriers by defects and therefore prolongs the corresponding carrier lifetime up to 440%per percent applied strain.Our results open a new avenue to enlarge the carrier lifetime of 2D MoS2,which will facilitate its applications in high-efficient optoelectronic and photovoltaic devices.
文摘Interface traps generated under hot carrier (HC) stress in LDD nMOST's are monitored by the direct current current voltage (DCIV) measurement technique and charge pumping (CP) technique.The measured and analyzed results show that the D peak in DCIV spectrum,which related to the drain region,is affected by a superfluous drain leakage current.The band trap band tunneling current is dominant of this current.
