We have investigated homoepitaxy of Al N films grown by molecular beam epitaxy(MBE)on Al N/sapphire templates.The MBE epitaxy of Al N at the low temperature range,which is suitable for Al Ga N,encounters significant c...We have investigated homoepitaxy of Al N films grown by molecular beam epitaxy(MBE)on Al N/sapphire templates.The MBE epitaxy of Al N at the low temperature range,which is suitable for Al Ga N,encounters significant challenge in preventing Al droplet and pits,since the migration and desorption rate of Al atom are very low.In contrast,by elevating the growth temperature,such a difficulty can be effectively overcome,and we were able to grow Al N films with much improved surface morphology and obtained step flow growth mode without any Al droplets and pits.The cathodoluminescence spectroscopy indicate that the impurity incorporation and defect generation in the Al N epilayers was suppressed by elevating the growth temperature.A systematic investigation on the influence of Al beam flux and growth temperature in a very wide range on the Al N films has been conducted,and a comprehensive growth diagram of MBE Al N has been obtained.展开更多
Polarization-induced two-dimensional hole gases(2DHG)in GaN/AlGaN/GaN heterostructures offer a promising pathway for advancing p-channel transistors.This work investigates the impact of p-GaN thickness on hole distrib...Polarization-induced two-dimensional hole gases(2DHG)in GaN/AlGaN/GaN heterostructures offer a promising pathway for advancing p-channel transistors.This work investigates the impact of p-GaN thickness on hole distribution and transport through temperature-dependent Hall measurements and TCAD simulations.It is demonstrated that the p-channel is composed of holes both in the p-GaN layer and in the 2DHG at the GaN/AlGaN heterointerface at 300 K,whereas at 77 K,the p-channel conduction is dominated solely by the 2DHG at the GaN/AlGaN heterointerface.The results also reveal the formation of a polarization-induced 2DHG at the GaN/AlGaN interface,exhibiting a high sheet density of 2.2×10^(13)cm^(-2)and a mobility of 16.2 cm^(2)·V^(-1)·s^(-1)at 300 K.The 2DHG sheet density remains nearly independent of p-GaN thickness when the p-GaN layer exceeds 30 nm.However,for p-GaN layers thinner than 30 nm,the 2DHG sheet density strongly depends on the p-GaN thickness,which is attributed to the gradual extension of the depletion region toward the GaN/AlGaN interface under the influence of surface trap states.展开更多
A p-i-i-n type AlG a N heterostructure avalanche photodiodes(APDs)is proposed to decrease the avalanche breakdown voltage and to realize higher gain by using high-Al-content AlG aN layer as multiplication layer and lo...A p-i-i-n type AlG a N heterostructure avalanche photodiodes(APDs)is proposed to decrease the avalanche breakdown voltage and to realize higher gain by using high-Al-content AlG aN layer as multiplication layer and low-Al-content AlG aN layer as absorption layer.The calculated results show that the designed APD can significantly reduce the breakdown voltage by almost 30%,and about sevenfold increase of maximum gain compared to the conventional Al GaN APD.The noise in designed APD is also less than that in conventional APD due to its low dark current at the breakdown voltage point.Moreover,the one-dimensional(1D)dual-periodic photonic crystal(PC)with anti-reflection coating filter is designed to achieve the solar-blind characteristic and cutoff wavelength of 282 nm is obtained.展开更多
The AlGaN/GaN p-n junction has received extensive attention due to its capability of rapid photogenerated carrier separation in photodetection devices.The AlGaN/GaN heterojunction nanowires(NWs)have been especially en...The AlGaN/GaN p-n junction has received extensive attention due to its capability of rapid photogenerated carrier separation in photodetection devices.The AlGaN/GaN heterojunction nanowires(NWs)have been especially endowed with new life for distinctive transport characteristics in the photoelectrochemical(PEC)detection field.A self-powered PEC ultraviolet photodetector(PEC UV PD)based on the p-AlGaN/n-GaN heterojunction NW is reported in this work.The n-GaN NW layer plays a crucial role as a current flow hub to regulate carrier transport,which mainly acts as a light absorber under 365 nm and carrier recombination layer under 255 nm illumination,which can effectively modulate photoresponsivity at different wavelengths.Furthermore,by designing the thicknesses of the NW layer,the photocurrent polarity reversal was successfully achieved in the constructed AlGaN/GaN NW PEC UV PD at two different light wavelengths.In addition,by combining with platinum decoration,the photoresponse performance could be further enhanced.Our work provides insight into transport mechanisms in the AlGaN/GaN NW PEC system,and offers a feasible and comprehensive strategy for further exploration of multifunctional optoelectronic devices.展开更多
Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a per...Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a perfect cavity structure for such resonance to occur.Here we report GaN-based microdisks with different diameters,based on a standard blue LED wafer on a Si substrate.A confocal photoluminescence spectroscopy is performed to analyze the properties of all microdisks.Then,we systematically study the effects of radial modes and axial modes of these microdisks on photon-electron coupling efficiency by using three-dimensional finite-difference time-domain simulations.For thick microdisks,photon-electron coupling efficiency is found to greatly depend on the distributions of both the radial modes and the axial modes,and the inclined sidewalls make significant influences on the axial mode distributions.These results are important for realization of high-efficiency resonant emission in GaN-based microcavity devices.展开更多
By introducing a thin p-type layer between the Schottky metal and n-GaN layer, this work presents a Schottky-pn junction diode(SPND) configuration for the GaN rectifier fabrication. Specific unipolar carrier conductio...By introducing a thin p-type layer between the Schottky metal and n-GaN layer, this work presents a Schottky-pn junction diode(SPND) configuration for the GaN rectifier fabrication. Specific unipolar carrier conduction characteristic is demonstrated by the verification of temperature-dependent current–voltage(I–V) tests and electroluminescence spectra.Meanwhile, apparently advantageous forward conduction properties as compared to the pn diode fabricated on the same wafer have been achieved, featuring a lower turn-on voltage of 0.82 V. Together with the analysis model established in the GaN SPND for a wide-range designable turn-on voltage, this work provides an alternative method to the GaN rectifier strategies besides the traditional solution.展开更多
In this work,a 4H-SiC-based soft X-ray single photon detector with photon energy resolution capability is demonstrated.The 4H-SiC p-i-n detector with an 80-μm-thick epi-layer and low intrinsic doping exhibits a low l...In this work,a 4H-SiC-based soft X-ray single photon detector with photon energy resolution capability is demonstrated.The 4H-SiC p-i-n detector with an 80-μm-thick epi-layer and low intrinsic doping exhibits a low leakage current of∼1.8 pA at−180 V,guaranteeing superior dark current performance for single photon detection with low electronic noise.An amplification strategy employing an active switch in the charge-sensitive amplifier has also been developed,where feedback-resistance-related thermal noise has been well eliminated,contributing to lower electronic noise in the amplification stage.By tuning the shaping time in the analog-to-digital circuit for precise signal processing,an optimal photon energy resolution has been achieved with a duration time within 6.4µs,achieving an energy analysis standard deviation below 5.7%.Ultimately,superior linearity has been obtained between the output pulse amplitude and the characteristic photon energy by utilizing a series of different metal targets,opening a new opportunity for advanced soft X-ray detection technology based on wide bandgap semiconductors.展开更多
The porous NiO nanoplates modified with rGO nanosheets and SnO_(2)nanoparticles are developed for accurate and rapid ppb-level NO_(2)detection.The developed SnO_(2)/NiO/rGO sensor towards 50 ppm NO_(2)gas demonstrates...The porous NiO nanoplates modified with rGO nanosheets and SnO_(2)nanoparticles are developed for accurate and rapid ppb-level NO_(2)detection.The developed SnO_(2)/NiO/rGO sensor towards 50 ppm NO_(2)gas demonstrates an excellent gas-sensing response of 14.8 at 23℃,which is 3.03 times that of Ni O/rGO sensor(4.89)and 6.49 times that of NiO sensor(2.28),respectively.The developed SnO_(2)/NiO/rGO sensor exhibits faster response/recovery speed(12.7/32.8 s@5 ppm),with extra-low theoretical detection limit of 0.15 ppb at room temperature.More fascinatingly,our sensors indicate great sensitivity,outstanding repeatability and long-term stability for longer than 7 weeks.Additionally,it also suggests that 1℃and 1%relative humidity have the same effect on the SnO_(2)/NiO/rGO sensor signal as approximately 13 ppb and 7.0 ppb NO_(2)gas change,respectively.Such excellent properties are mainly attributed to the large surface-to-volume ratio,which provides active sites to NO_(2)gas spread,adsorption and diffusion on material surface in redox reaction.Moreover,the ternary heterojunctions formed by NiO,rGO and SnO_(2)may serve as highly conductive channels to accelerate carrier transfer and abundant oxygen vacancies to reduce the adsorption energy for O_(2)and NO_(2)gas,thus further improving performance of the sensors.展开更多
Solar-blind ultraviolet(UV)photodetectors(PDs)have attracted tremendous attention in the environmental,industrial,military,and biological fields.As a representative Ill-nitride material,AlGaN alloys have broad develop...Solar-blind ultraviolet(UV)photodetectors(PDs)have attracted tremendous attention in the environmental,industrial,military,and biological fields.As a representative Ill-nitride material,AlGaN alloys have broad development prospects in the field of solar-blind detection due to their superior properties,such as tunable wide bandgaps for intrinsic UV detection.In recent decades,a variety of AlGaN-based PDs have been developed to achieve high-precision solar-blind UV detection.As integrated optoelectronic technology advances,AlGaN-based focal plane arrays(FPAs)are manufactured and exhibit outsta nding solar-blind imaging capability.Con sidering the rapid development of AlGaN detection techniques,this paper comprehensively reviews the progress on AlGaN-based solar-blind UV PDs and FPAs.First,the basic physical properties of AlGaN are presented.The epitaxy and p-type doping problems of AlGaN alloys are then discussed.Diverse PDs,including photoconductors and Schottky,metal-semiconductor-metal(MSM),p-i-n,and avalanche photodiodes(APDs),are dem on strated,and the physical mechanisms are analyzed to improve device performance.Additionally,this paper summarizes imaging technologies used with AlGaN FPAs in recent years.Benefit!ng from the development of AlGaN materials and optoelectronic devices,solar-blind UV detection technology is greeted with significant revolutions.展开更多
We fabricated p-i-n tunnel junction(TJ)contacts for hole injection on c-plane green micro-light-emitting diodes(micro-LEDs)by a hybrid growth approach using plasma-assisted molecular beam epitaxy(PA-MBE)and metal–org...We fabricated p-i-n tunnel junction(TJ)contacts for hole injection on c-plane green micro-light-emitting diodes(micro-LEDs)by a hybrid growth approach using plasma-assisted molecular beam epitaxy(PA-MBE)and metal–organic chemical vapor deposition(MOCVD).The TJ was formed by an MBE-grown ultra-thin unintentionally doped In Ga N polarization layer and an n^(++)∕n^(+)-GaN layer on the activated p^(++)-Ga N layer prepared by MOCVD.This hybrid growth approach allowed for the realization of a steep doping interface and ultrathin depletion width for efficient inter-band tunneling.Compared to standard micro-LEDs,the TJ micro-LEDs showed a reduced device resistance,enhanced electroluminescence intensity,and a reduced efficiency droop.The size-independent J-V characteristics indicate that TJ could serve as an excellent current spreading layer.All these results demonstrated that hybrid TJ contacts contributed to the realization of high-performance micro-LEDs with long emission wavelengths.展开更多
The reverse leakage characteristics of AlGaNbased ultraviolet light-emitting diodes fabricated on sapphire substrate are studied by temperature-variable current–voltage(I–V)measurement from 300 to 450 K.At low-rever...The reverse leakage characteristics of AlGaNbased ultraviolet light-emitting diodes fabricated on sapphire substrate are studied by temperature-variable current–voltage(I–V)measurement from 300 to 450 K.At low-reverse bias range(0–0.5 V),the reverse leakage current exhibits tunneling characteristics.Meanwhile,under a more negative reverse bias range([0.5 V),the log(I)–log(V)plots exhibit close-to-linear dependency,which is in good agreement with the transport mechanism of space-charge limited current.A phenomenological leakage current model focusing on electron transmission primarily through continuous defect band formed by linear defects like dislocations is suggested to explain the reverse current–voltage characteristics.展开更多
In this work, a GaN p-i-n diode based on Mg ion implantation for visible-blind UV detection is demonstrated.With an optimized implantation and annealing process, a p-GaN layer and corresponding GaN p-i-n photodiode ar...In this work, a GaN p-i-n diode based on Mg ion implantation for visible-blind UV detection is demonstrated.With an optimized implantation and annealing process, a p-GaN layer and corresponding GaN p-i-n photodiode are achieved via Mg implantation. As revealed in the UV detection characterizations, these diodes exhibit a sharp wavelength cutoff at 365 nm, high UV/visible rejection ratio of 1.2 × 10~4, and high photoresponsivity of 0.35 A/W, and are proved to be comparable with commercially available GaN p-n photodiodes. Additionally, a localized states-related gain mechanism is systematically investigated, and a relevant physics model of electricfield-assisted photocarrier hopping is proposed. The demonstrated Mg ion-implantation-based approach is believed to be an applicable and CMOS-process-compatible technology for GaN-based p-i-n photodiodes.展开更多
Understanding detailed avalanche mechanisms is critical for design optimization of avalanche photodiodes(APDs).In this work,avalanche characteristics and single photon counting performance of 4H-SiC n-i-p and p-i-n AP...Understanding detailed avalanche mechanisms is critical for design optimization of avalanche photodiodes(APDs).In this work,avalanche characteristics and single photon counting performance of 4H-SiC n-i-p and p-i-n APDs are compared.By studying the evolution of breakdown voltage as a function of incident light wavelength,it is confirmed that at the deep ultraviolet(UV)wavelength region the avalanche events in 4H-SiC n-i-p APDs are mainly induced by hole-initiated ionization,while electron-initiated ionization is the main cause of avalanche breakdown in 4H-SiC p-i-n APDs.Meanwhile,at the same dark count rate,the single photon counting efficiency of n-i-p APDs is considerably higher than that of p-i-n APDs.The higher performance of n-i-p APDs can be explained by the larger impact ionization coefficient of holes in 4H-SiC.In addition,this is the first time,to the best of our knowledge,to report single photon detection performance of vertical 4H-SiC n-i-p-n APDs.展开更多
GaN power electronic devices,such as the lateral AlGaN/GaN Schottky barrier diode(SBD),have received significant attention in recent years.Many studies have focused on optimizing the breakdown voltage(BV)of the device...GaN power electronic devices,such as the lateral AlGaN/GaN Schottky barrier diode(SBD),have received significant attention in recent years.Many studies have focused on optimizing the breakdown voltage(BV)of the device,with a particular emphasis on achieving ultra-high-voltage(UHV,>10 kV)applications.However,another important question arises:can the device maintain a BV of 10 kV while having a low turn-on voltage(V_(on))?In this study,the fabrication of UHV AlGaN/GaN SBDs was demonstrated on sapphire with a BV exceeding 10 kV.Moreover,by utilizing a doublebarrier anode(DBA)structure consisting of platinum(Pt)and tantalum(Ta),a remarkably low Von of 0.36 V was achieved.This achievement highlights the great potential of these devices for UHV applications.展开更多
In this Letter, we demonstrate ultraviolet(UV) spot position measurement based on the 4 H-SiC quadrant photodetectors(QPDs). The 4 H-SiC QPD with an 8 mm × 8 mm active area exhibits high uniformity across four qu...In this Letter, we demonstrate ultraviolet(UV) spot position measurement based on the 4 H-SiC quadrant photodetectors(QPDs). The 4 H-SiC QPD with an 8 mm × 8 mm active area exhibits high uniformity across four quadrants, with a consistent low dark current of ~18 p A and a responsivity of 0.111 A/W at 275 nm. Based on the QPD, the prototype system shows high positioning capability with a slight inherent nonlinearity. Correspondingly, the measurement error is analyzed and a calibration method utilizing the Boltzmann function is developed for the error correction. Evident improvement in positioning accuracy of the measurement system has been realized, achieving a position resolution of 0.3 μm and a mean positioning error of ~28.5 μm.展开更多
基金Project supported by the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0303400)the National Key Research and Development Program of China(Grant Nos.2022YFB3605602 and 2024YFE0205000)+1 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20243037)the Jiangsu Special Professorship,Collaborative Innovation Center of Solid-state Lighting and Energy-saving Electronics,Postdoctoral Fellowship Program of CPSF(Grant No.GZC20231098)。
文摘We have investigated homoepitaxy of Al N films grown by molecular beam epitaxy(MBE)on Al N/sapphire templates.The MBE epitaxy of Al N at the low temperature range,which is suitable for Al Ga N,encounters significant challenge in preventing Al droplet and pits,since the migration and desorption rate of Al atom are very low.In contrast,by elevating the growth temperature,such a difficulty can be effectively overcome,and we were able to grow Al N films with much improved surface morphology and obtained step flow growth mode without any Al droplets and pits.The cathodoluminescence spectroscopy indicate that the impurity incorporation and defect generation in the Al N epilayers was suppressed by elevating the growth temperature.A systematic investigation on the influence of Al beam flux and growth temperature in a very wide range on the Al N films has been conducted,and a comprehensive growth diagram of MBE Al N has been obtained.
基金supported by the National Key Research and Development Program of China(Grant No.2024YFE0205000)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20243037)+2 种基金the National Natural Science Foundation of China(Grant Nos.62074077 and 61921005)the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20231098)the Collab-orative Innovation Center of Solid State Lighting and Energy-Saving Electronics.
文摘Polarization-induced two-dimensional hole gases(2DHG)in GaN/AlGaN/GaN heterostructures offer a promising pathway for advancing p-channel transistors.This work investigates the impact of p-GaN thickness on hole distribution and transport through temperature-dependent Hall measurements and TCAD simulations.It is demonstrated that the p-channel is composed of holes both in the p-GaN layer and in the 2DHG at the GaN/AlGaN heterointerface at 300 K,whereas at 77 K,the p-channel conduction is dominated solely by the 2DHG at the GaN/AlGaN heterointerface.The results also reveal the formation of a polarization-induced 2DHG at the GaN/AlGaN interface,exhibiting a high sheet density of 2.2×10^(13)cm^(-2)and a mobility of 16.2 cm^(2)·V^(-1)·s^(-1)at 300 K.The 2DHG sheet density remains nearly independent of p-GaN thickness when the p-GaN layer exceeds 30 nm.However,for p-GaN layers thinner than 30 nm,the 2DHG sheet density strongly depends on the p-GaN thickness,which is attributed to the gradual extension of the depletion region toward the GaN/AlGaN interface under the influence of surface trap states.
基金supported by Anhui University Natural Science Research Project, China (KJ2015A153)Initial research fund from Chuzhou University, China (2014qd024)+1 种基金The Higher Education Excellent Youth Talents Foundation of Anhui Province (gxyqZ D2016329)the Anhui Provincial Natural Science Foundation of China under Grant (1708085MF149)
文摘A p-i-i-n type AlG a N heterostructure avalanche photodiodes(APDs)is proposed to decrease the avalanche breakdown voltage and to realize higher gain by using high-Al-content AlG aN layer as multiplication layer and low-Al-content AlG aN layer as absorption layer.The calculated results show that the designed APD can significantly reduce the breakdown voltage by almost 30%,and about sevenfold increase of maximum gain compared to the conventional Al GaN APD.The noise in designed APD is also less than that in conventional APD due to its low dark current at the breakdown voltage point.Moreover,the one-dimensional(1D)dual-periodic photonic crystal(PC)with anti-reflection coating filter is designed to achieve the solar-blind characteristic and cutoff wavelength of 282 nm is obtained.
基金supported by the National Key R&D Program of China(Grant No.2022YFB3605403)the Natural Science Foundation of Jiangsu Province(Grant Nos.BK20200094 and BK20210577)+3 种基金the National Natural Science Foundation of China(Grant Nos.62004104 and 62104110)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.21KJB140020)the Jiangsu Provincial Double-Innovation Doctor Program(Grant No.JSSCBS20210529)the Natural Science Foundation of Jiangsu Province-Major Project(Grant No.BK20212012).
文摘The AlGaN/GaN p-n junction has received extensive attention due to its capability of rapid photogenerated carrier separation in photodetection devices.The AlGaN/GaN heterojunction nanowires(NWs)have been especially endowed with new life for distinctive transport characteristics in the photoelectrochemical(PEC)detection field.A self-powered PEC ultraviolet photodetector(PEC UV PD)based on the p-AlGaN/n-GaN heterojunction NW is reported in this work.The n-GaN NW layer plays a crucial role as a current flow hub to regulate carrier transport,which mainly acts as a light absorber under 365 nm and carrier recombination layer under 255 nm illumination,which can effectively modulate photoresponsivity at different wavelengths.Furthermore,by designing the thicknesses of the NW layer,the photocurrent polarity reversal was successfully achieved in the constructed AlGaN/GaN NW PEC UV PD at two different light wavelengths.In addition,by combining with platinum decoration,the photoresponse performance could be further enhanced.Our work provides insight into transport mechanisms in the AlGaN/GaN NW PEC system,and offers a feasible and comprehensive strategy for further exploration of multifunctional optoelectronic devices.
基金the National Key R&D Program of China(Grant Nos.2016YFB0400102 and 2016YFB0400602)the National Natural Science Foundation of China(Grant Nos.61674076,61422401 and 51461135002)+2 种基金the Collaborative Innovation Center of Solid State Lighting and Energy-Saving Electronics,Open Fund of the State Key Laboratory on Integrated Optoelectronics(Grant No.IOSKL2017KF03)the Natural Science Foundation for Young Scientists of Jiangsu Province of China(Grant No.BK20160376)the Research Funds from NJU-Yangzhou Institute of Opto-electronics,and the Research and Development Funds from State Grid Shandong Electric Power Company and Electric Power Research Institute.
文摘Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a perfect cavity structure for such resonance to occur.Here we report GaN-based microdisks with different diameters,based on a standard blue LED wafer on a Si substrate.A confocal photoluminescence spectroscopy is performed to analyze the properties of all microdisks.Then,we systematically study the effects of radial modes and axial modes of these microdisks on photon-electron coupling efficiency by using three-dimensional finite-difference time-domain simulations.For thick microdisks,photon-electron coupling efficiency is found to greatly depend on the distributions of both the radial modes and the axial modes,and the inclined sidewalls make significant influences on the axial mode distributions.These results are important for realization of high-efficiency resonant emission in GaN-based microcavity devices.
基金supported by the National Natural Science Foundation of China (Grant Nos. U2141241, 62004099, 61921005,and 91850112)。
文摘By introducing a thin p-type layer between the Schottky metal and n-GaN layer, this work presents a Schottky-pn junction diode(SPND) configuration for the GaN rectifier fabrication. Specific unipolar carrier conduction characteristic is demonstrated by the verification of temperature-dependent current–voltage(I–V) tests and electroluminescence spectra.Meanwhile, apparently advantageous forward conduction properties as compared to the pn diode fabricated on the same wafer have been achieved, featuring a lower turn-on voltage of 0.82 V. Together with the analysis model established in the GaN SPND for a wide-range designable turn-on voltage, this work provides an alternative method to the GaN rectifier strategies besides the traditional solution.
基金supported by the Innovation Program for Quantum Science and Technology(No.2021ZD0303400)the National Natural Science Foundation of China(Nos.62374084,61921005,62104102,U2141241,and U21A20496)+1 种基金the Jiangsu Provincial Key Research and Development Program(No.BE2023018)the Fundamental Research Funds for the Central Universities.
文摘In this work,a 4H-SiC-based soft X-ray single photon detector with photon energy resolution capability is demonstrated.The 4H-SiC p-i-n detector with an 80-μm-thick epi-layer and low intrinsic doping exhibits a low leakage current of∼1.8 pA at−180 V,guaranteeing superior dark current performance for single photon detection with low electronic noise.An amplification strategy employing an active switch in the charge-sensitive amplifier has also been developed,where feedback-resistance-related thermal noise has been well eliminated,contributing to lower electronic noise in the amplification stage.By tuning the shaping time in the analog-to-digital circuit for precise signal processing,an optimal photon energy resolution has been achieved with a duration time within 6.4µs,achieving an energy analysis standard deviation below 5.7%.Ultimately,superior linearity has been obtained between the output pulse amplitude and the characteristic photon energy by utilizing a series of different metal targets,opening a new opportunity for advanced soft X-ray detection technology based on wide bandgap semiconductors.
基金funded by the National Natural Science Foundation of China(No.62364002)Key Scientific Research Projects of Universities in Henan Province(No.24A510014)+5 种基金Xinjiang-Changji Vocational Education Alliance Special Project(No.2050305)National Laboratory of Solid State Microstructures,Nanjing University(No.M36001)Jiangsu Key Laboratory of Optoelectronic Information Functional Materials,Nanjing University(No.ndgd2024005)Henan Province Higher Education College Student Innovation Training Program Project(No.202410478019)the Doctoral Research Initiation Fund Project,Zhoukou Normal University(No.ZKNUC2022018)the Natural Science Foundation Project of Xinjiang Uygur Autonomous Region(No.2022D01C006)。
文摘The porous NiO nanoplates modified with rGO nanosheets and SnO_(2)nanoparticles are developed for accurate and rapid ppb-level NO_(2)detection.The developed SnO_(2)/NiO/rGO sensor towards 50 ppm NO_(2)gas demonstrates an excellent gas-sensing response of 14.8 at 23℃,which is 3.03 times that of Ni O/rGO sensor(4.89)and 6.49 times that of NiO sensor(2.28),respectively.The developed SnO_(2)/NiO/rGO sensor exhibits faster response/recovery speed(12.7/32.8 s@5 ppm),with extra-low theoretical detection limit of 0.15 ppb at room temperature.More fascinatingly,our sensors indicate great sensitivity,outstanding repeatability and long-term stability for longer than 7 weeks.Additionally,it also suggests that 1℃and 1%relative humidity have the same effect on the SnO_(2)/NiO/rGO sensor signal as approximately 13 ppb and 7.0 ppb NO_(2)gas change,respectively.Such excellent properties are mainly attributed to the large surface-to-volume ratio,which provides active sites to NO_(2)gas spread,adsorption and diffusion on material surface in redox reaction.Moreover,the ternary heterojunctions formed by NiO,rGO and SnO_(2)may serve as highly conductive channels to accelerate carrier transfer and abundant oxygen vacancies to reduce the adsorption energy for O_(2)and NO_(2)gas,thus further improving performance of the sensors.
基金the National Key R&D Program of China(2016YFB0400903)the NSFC(61634002),and the NSAF(U1830109).
文摘Solar-blind ultraviolet(UV)photodetectors(PDs)have attracted tremendous attention in the environmental,industrial,military,and biological fields.As a representative Ill-nitride material,AlGaN alloys have broad development prospects in the field of solar-blind detection due to their superior properties,such as tunable wide bandgaps for intrinsic UV detection.In recent decades,a variety of AlGaN-based PDs have been developed to achieve high-precision solar-blind UV detection.As integrated optoelectronic technology advances,AlGaN-based focal plane arrays(FPAs)are manufactured and exhibit outsta nding solar-blind imaging capability.Con sidering the rapid development of AlGaN detection techniques,this paper comprehensively reviews the progress on AlGaN-based solar-blind UV PDs and FPAs.First,the basic physical properties of AlGaN are presented.The epitaxy and p-type doping problems of AlGaN alloys are then discussed.Diverse PDs,including photoconductors and Schottky,metal-semiconductor-metal(MSM),p-i-n,and avalanche photodiodes(APDs),are dem on strated,and the physical mechanisms are analyzed to improve device performance.Additionally,this paper summarizes imaging technologies used with AlGaN FPAs in recent years.Benefit!ng from the development of AlGaN materials and optoelectronic devices,solar-blind UV detection technology is greeted with significant revolutions.
基金Collaborative Innovation Center of Solid State Lighting and Energy-Saving ElectronicsLeading-Edge Technology Program of Jiangsu Natural Science Foundation(BK20202005)+1 种基金National Natural Science Foundation of China(61921005,61974062,62074077)National Key Research and Development Program of China(2017YFB0403100,2017YFB0403101)。
文摘We fabricated p-i-n tunnel junction(TJ)contacts for hole injection on c-plane green micro-light-emitting diodes(micro-LEDs)by a hybrid growth approach using plasma-assisted molecular beam epitaxy(PA-MBE)and metal–organic chemical vapor deposition(MOCVD).The TJ was formed by an MBE-grown ultra-thin unintentionally doped In Ga N polarization layer and an n^(++)∕n^(+)-GaN layer on the activated p^(++)-Ga N layer prepared by MOCVD.This hybrid growth approach allowed for the realization of a steep doping interface and ultrathin depletion width for efficient inter-band tunneling.Compared to standard micro-LEDs,the TJ micro-LEDs showed a reduced device resistance,enhanced electroluminescence intensity,and a reduced efficiency droop.The size-independent J-V characteristics indicate that TJ could serve as an excellent current spreading layer.All these results demonstrated that hybrid TJ contacts contributed to the realization of high-performance micro-LEDs with long emission wavelengths.
基金supported by the National Basic Research Program of China(2010CB327504 and 2011CB301900)the National Natural Science Foundation of China(60825401 and60936004)+1 种基金the Fundamental Research Funds for the Central Universities(JUSRP51323B)the National Science Foundation of Jiangsu Province(BK2012110)
文摘The reverse leakage characteristics of AlGaNbased ultraviolet light-emitting diodes fabricated on sapphire substrate are studied by temperature-variable current–voltage(I–V)measurement from 300 to 450 K.At low-reverse bias range(0–0.5 V),the reverse leakage current exhibits tunneling characteristics.Meanwhile,under a more negative reverse bias range([0.5 V),the log(I)–log(V)plots exhibit close-to-linear dependency,which is in good agreement with the transport mechanism of space-charge limited current.A phenomenological leakage current model focusing on electron transmission primarily through continuous defect band formed by linear defects like dislocations is suggested to explain the reverse current–voltage characteristics.
基金National Key R&D Program of China(2017YFB0403000)National Natural Science Foundation of China(NSFC)(61774081,91850112)+3 种基金Natural Science Foundation of Jiangsu Province(BK20161401)Fundamental Research Funds for the Central Universities(021014380085,021014380093,021014380098)Priority Academic Program Development of Jiangsu Higher Education InstitutionsScience and Technology Project of State Grid Corporation of China(SGSDDK00KJJS1600071)
文摘In this work, a GaN p-i-n diode based on Mg ion implantation for visible-blind UV detection is demonstrated.With an optimized implantation and annealing process, a p-GaN layer and corresponding GaN p-i-n photodiode are achieved via Mg implantation. As revealed in the UV detection characterizations, these diodes exhibit a sharp wavelength cutoff at 365 nm, high UV/visible rejection ratio of 1.2 × 10~4, and high photoresponsivity of 0.35 A/W, and are proved to be comparable with commercially available GaN p-n photodiodes. Additionally, a localized states-related gain mechanism is systematically investigated, and a relevant physics model of electricfield-assisted photocarrier hopping is proposed. The demonstrated Mg ion-implantation-based approach is believed to be an applicable and CMOS-process-compatible technology for GaN-based p-i-n photodiodes.
基金supported by the National Key R&D Program of China (No.2016YFB0400902)the National Natural Science Foundation of China (Nos.61921005 and 62004098)+1 种基金the Natural Science Foundation of Jiangsu Province (No. BK20190302)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Understanding detailed avalanche mechanisms is critical for design optimization of avalanche photodiodes(APDs).In this work,avalanche characteristics and single photon counting performance of 4H-SiC n-i-p and p-i-n APDs are compared.By studying the evolution of breakdown voltage as a function of incident light wavelength,it is confirmed that at the deep ultraviolet(UV)wavelength region the avalanche events in 4H-SiC n-i-p APDs are mainly induced by hole-initiated ionization,while electron-initiated ionization is the main cause of avalanche breakdown in 4H-SiC p-i-n APDs.Meanwhile,at the same dark count rate,the single photon counting efficiency of n-i-p APDs is considerably higher than that of p-i-n APDs.The higher performance of n-i-p APDs can be explained by the larger impact ionization coefficient of holes in 4H-SiC.In addition,this is the first time,to the best of our knowledge,to report single photon detection performance of vertical 4H-SiC n-i-p-n APDs.
基金supported by National Key R&D Project grant No.2022YFE0122700)National High-Tech R&D Project(grant No.2015AA033305)+2 种基金Jiangsu Provincial Key R&D Program(grant No.BK2015111)China Postdoctoral Science Foundation(grant No.2023M731583)Jiangsu Provincial Innovation and Entrepreneurship Doctor Program,the Research and Development Funds from State Grid Shandong Electric Power Company and Electric Power Research Institute.
文摘GaN power electronic devices,such as the lateral AlGaN/GaN Schottky barrier diode(SBD),have received significant attention in recent years.Many studies have focused on optimizing the breakdown voltage(BV)of the device,with a particular emphasis on achieving ultra-high-voltage(UHV,>10 kV)applications.However,another important question arises:can the device maintain a BV of 10 kV while having a low turn-on voltage(V_(on))?In this study,the fabrication of UHV AlGaN/GaN SBDs was demonstrated on sapphire with a BV exceeding 10 kV.Moreover,by utilizing a doublebarrier anode(DBA)structure consisting of platinum(Pt)and tantalum(Ta),a remarkably low Von of 0.36 V was achieved.This achievement highlights the great potential of these devices for UHV applications.
基金supported by the Innovation Program for Quantum Science and Technology (No.2021ZD0303400)the National Natural Science Foundation of China (Nos.61921005,U2141241,62374084,and U21A20496)the Key Research Program of Jiangsu Province (No.BE2023018)。
文摘In this Letter, we demonstrate ultraviolet(UV) spot position measurement based on the 4 H-SiC quadrant photodetectors(QPDs). The 4 H-SiC QPD with an 8 mm × 8 mm active area exhibits high uniformity across four quadrants, with a consistent low dark current of ~18 p A and a responsivity of 0.111 A/W at 275 nm. Based on the QPD, the prototype system shows high positioning capability with a slight inherent nonlinearity. Correspondingly, the measurement error is analyzed and a calibration method utilizing the Boltzmann function is developed for the error correction. Evident improvement in positioning accuracy of the measurement system has been realized, achieving a position resolution of 0.3 μm and a mean positioning error of ~28.5 μm.
