Theβ-Ga_(2)O_(3)films with different thicknesses are prepared by an atomic layer deposition system.The influence of film thickness on the crystal quality is obvious,indicating that the thicker films perform better cr...Theβ-Ga_(2)O_(3)films with different thicknesses are prepared by an atomic layer deposition system.The influence of film thickness on the crystal quality is obvious,indicating that the thicker films perform better crystal quality,which is verified from x-ray diffraction(XRD)and scanning electron microscope(SEM)results.The Ga_(2)O_(3)-based solar blind photodetectors with different thicknesses are fabricated and studied.The experimental results show that the responsivity of the photodetectors increases exponentially with the increase of the film thickness.The photodetectors with inter-fingered structure based on 900 growth cyclesβ-Ga_(2)O_(3)active layers(corresponding film thickness of 58 nm)exhibit the best performances including a low dark current of 134 fA,photo-to-dark current ratio of 1.5×10^(7),photoresponsivity of 1.56 A/W,detectivity of 2.77×10^(14)Jones,and external quantum efficiency of 764.49%at a bias voltage of 10 V under 254-nm DUV illumination.The photoresponse rejection ratio(R_(254)/R_(365))is up to 1.86×10^(5).In addition,we find that the photoelectric characteristics also depend on the finger spacing of the MSM structure.As the finger spacing decreases from 50μm to10μW,the photoresponsivity,detectivity,and external quantum efficiency increase significantly.展开更多
We report on the transition of photovoltaic and photoconductive operation modes of the amorphous Ga_2O_3-based solar-blind photodetectors in metal–semiconductor–metal(MSM) configurations. The conversion from Ohmic t...We report on the transition of photovoltaic and photoconductive operation modes of the amorphous Ga_2O_3-based solar-blind photodetectors in metal–semiconductor–metal(MSM) configurations. The conversion from Ohmic to Schottky contacts at Ti/Ga_2O_3 interface is realized by tuning the conductivity of amorphous Ga_2O_3 films with delicate control of oxygen flux in the sputtering process. The abundant donor-like oxygen vacancies distributed near the Ti/Ga_2O_3 interface fascinate the tunneling process across the barrier and result in the formation of Ohmic contacts. As a consequence, the serious sub-gap absorption and persistent photoconductivity(PPC) effect degrades the performance of the photoconductive detectors. In contrast, the photovoltaic device with a Schottky contact exhibits an ultra-low dark current less than 1 pA,a high detectivity of 9.82×10^(12) cm·Hz^(1/2)·W^(-1), a fast response time of 243.9 μs, and a high ultraviolet C(UVC)-toultraviolet A(UVA) rejection ratio of 103. The promoting performance is attributed primarily to the reduction of the subgap states and the resultant suppression of PPC effect. With simple architecture, low fabrication cost, and easy fusion with modern high-speed integrated circuitry, these results provide a cost-effective way to realize high performance solar-blind photodetectors towards versatile practical applications.展开更多
In the present work, we explore the solar-blind ultraviolet（UV） photodetectors（PDs） with enhanced photoresponse,fabricated on Ga/Ga2O3 nanocomposite films. Through pre-burying metal Ga layers and thermally post-an...In the present work, we explore the solar-blind ultraviolet（UV） photodetectors（PDs） with enhanced photoresponse,fabricated on Ga/Ga2O3 nanocomposite films. Through pre-burying metal Ga layers and thermally post-annealing the laminated Ga2 O3/Ga/Ga2O3 structures, Ga/Ga2O3 nanocomposite films incorporated with Ga nanospheres are obtained. For the prototype PD, it is found that the photocurrent and photoresponsivity will first increase and then decrease monotonically with the thickness of the pre-buried Ga layer increasing. Each of all PDs shows a spectrum response peak at 260 nm, demonstrating the ability to detect solar-blind UV light. Adjustable photoresponse enhancement factors are achieved by means of the surface plasmon in the nanocomposite films. The PD with a 20 nm thick Ga interlayer exhibits the best solar-blind UV photoresponse characteristics with an extremely low dark current of 8.52 p A at 10-V bias, a very high light-to-dark ratio of ～ 8 × 10~5, a large photoresponsivity of 2.85 A/W at 15-V bias, and a maximum enhancement factor of ～ 220. Our research provides a simple and practical route to high performance solar-blind UV PDs and potential applications in the field of optoelectronics.展开更多
A solar-blind photodetector is fabricated on single crystal Ga_2O_3 based on vertical structure Schottky barrier diode. A Cu Schottky contact electrode is prepared in a honeycomb porous structure to increase the ultra...A solar-blind photodetector is fabricated on single crystal Ga_2O_3 based on vertical structure Schottky barrier diode. A Cu Schottky contact electrode is prepared in a honeycomb porous structure to increase the ultraviolet(UV) transmittance.The quantum efficiency is about 400% at 42 V. The Ga_2O_3 photodetector shows a sharp cutoff wavelength at 259 nm with high solar-blind/visible(= 3213) and solar-blind/UV(= 834) rejection ratio. Time-resolved photoresponse of the photodetector is investigated at 253-nm illumination from room temperature(RT) to 85.8℃. The photodetector maintains a high reversibility and response speed, even at high temperatures.展开更多
Heterojunctions composed ofβ-Ga2 O3 and ZnO films are fabricated on sapphire substrates by using the laser molecular beam epitaxy method.The heterojunction possesses excellent rectifying characteristics with an asymm...Heterojunctions composed ofβ-Ga2 O3 and ZnO films are fabricated on sapphire substrates by using the laser molecular beam epitaxy method.The heterojunction possesses excellent rectifying characteristics with an asymmetry ratio over 105.Prominent solar-blind photoresponse effect is also observed in the formed heterojunction.The photodetector exhibits a self-powered behavior with a fast response speed(rise time and decay time are 0.035 s and 0.032 s respectively)at zero bias.The obtained high performance can be related to the built-in field driven photogenerated electron-hole separation.展开更多
Gallium oxide(Ga_2O_3) thin films were deposited on a-Al2O3(1120) substrates by pulsed laser deposition(PLD) with different oxygen pressures at 650?C. By reducing the oxygen pressure, mixed-phase Ga_2O_3 films with α...Gallium oxide(Ga_2O_3) thin films were deposited on a-Al2O3(1120) substrates by pulsed laser deposition(PLD) with different oxygen pressures at 650?C. By reducing the oxygen pressure, mixed-phase Ga_2O_3 films with α and β phases can be obtained, and on the basis of this, mixed-phase Ga_2O_3 thin film solar-blind photodetectors(SBPDs) were prepared.Comparing the responsivities of the mixed-phase Ga_2O_3 SBPDs and the single β-Ga_2O_3 SBPDs at a bias voltage of 25 V,it is found that the former has a maximum responsivity of approximately 12 A/W, which is approximately two orders of magnitude larger than that of the latter. This result shows that the mixed-phase structure of Ga_2O_3 thin films can be used to prepare high-responsivity SBPDs. Moreover, the cause of this phenomenon was investigated, which will provide a feasible way to improve the responsivity of Ga_2O_3 thin film SBPDs.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
Solar-blind ultraviolet photodetectors have many advantages, such as low false alarm rates, the ability to detect weak signals, and high signal-to-noise ratios. Among the various functional solar-blind ultraviolet pho...Solar-blind ultraviolet photodetectors have many advantages, such as low false alarm rates, the ability to detect weak signals, and high signal-to-noise ratios. Among the various functional solar-blind ultraviolet photodetectors, Ga-based alloys of AlGaN and Ga_2O_3 are the most commonly adopted channel semiconductor materials and have attracted extensive research attention in the past decades. This review presents an overview of the recent progress in Ga-based solar-blind photodetectors. In case of AlGaN-based solar-blind ultraviolet photodetectors, the response properties can be improved by optimizing the AlN nucleation layer and designing the avalanche structure. On the other hand, we also discuss the morphology and growth methods of Ga_2O_3 nanomaterials and their effect on the performance of the corresponding solarblind photodetectors. The mechanically exfoliated Ga_2O_3 flakes show good potential for ultraviolet detection. Also, Ga_2O_3 nanoflowers and nanowires reveal perfect response to ultraviolet light. Finally, the challenges and future development of Ga-based functional solar-blind ultraviolet photodetectors are summarized.展开更多
We have developed a superior solar-blind ultraviolet （UV） photocathode with an AlxGa1_xrN photocathode （x ～ 0.45） in semi-transparent mode, and assessed spectra radiant sensitivity related to practical use. Betbr...We have developed a superior solar-blind ultraviolet （UV） photocathode with an AlxGa1_xrN photocathode （x ～ 0.45） in semi-transparent mode, and assessed spectra radiant sensitivity related to practical use. Betbre being grown over a basal plane sapphire substrate by low-pressure metal organic chemical vapor deposition （MOCVD）, a reasonable design was made to the photocathode epitaxy structure, focusing on the AlxGa1_xN： Mg active layer, then followed by a comprehen- sive analysis of the structural and optical characterization. The spectra radiant sensitivity is peaked of 41.395 mA/W at wavelength 257 nm and then decreases by about 3 to 4 decades at 400 nm demonstrating the ability of this photocathode for solar-blind application prospects.展开更多
Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiatio...Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.展开更多
基金Project supported by the Natural Science Basic Research Program of Shaanxi Province,China(Grant No.2022JQ-701)the Scientific Research Program Funded by Shaanxi Provincial Education Department,China(Grant No.21JK0919)。
文摘Theβ-Ga_(2)O_(3)films with different thicknesses are prepared by an atomic layer deposition system.The influence of film thickness on the crystal quality is obvious,indicating that the thicker films perform better crystal quality,which is verified from x-ray diffraction(XRD)and scanning electron microscope(SEM)results.The Ga_(2)O_(3)-based solar blind photodetectors with different thicknesses are fabricated and studied.The experimental results show that the responsivity of the photodetectors increases exponentially with the increase of the film thickness.The photodetectors with inter-fingered structure based on 900 growth cyclesβ-Ga_(2)O_(3)active layers(corresponding film thickness of 58 nm)exhibit the best performances including a low dark current of 134 fA,photo-to-dark current ratio of 1.5×10^(7),photoresponsivity of 1.56 A/W,detectivity of 2.77×10^(14)Jones,and external quantum efficiency of 764.49%at a bias voltage of 10 V under 254-nm DUV illumination.The photoresponse rejection ratio(R_(254)/R_(365))is up to 1.86×10^(5).In addition,we find that the photoelectric characteristics also depend on the finger spacing of the MSM structure.As the finger spacing decreases from 50μm to10μW,the photoresponsivity,detectivity,and external quantum efficiency increase significantly.
基金Project supported by the National Key Research and Development Project,China(Grant No.2017YFB0403003)the National Natural Science Foundation of China(Grant Nos.61774081,61322403,and 91850112)+3 种基金the State Key Research and Development Project of Jiangsu Province,China(Grant No.BE2018115)Shenzhen Fundamental Research Project,China(Grant Nos.201773239 and 201888588)the Project of the State Key Laboratory of Wide-Bandgap Semiconductor Power Electric Devices,China(Grant No.2017KF001)the Fundamental Research Funds for the Central Universities,China(Grant Nos.021014380093 and 021014380085)
文摘We report on the transition of photovoltaic and photoconductive operation modes of the amorphous Ga_2O_3-based solar-blind photodetectors in metal–semiconductor–metal(MSM) configurations. The conversion from Ohmic to Schottky contacts at Ti/Ga_2O_3 interface is realized by tuning the conductivity of amorphous Ga_2O_3 films with delicate control of oxygen flux in the sputtering process. The abundant donor-like oxygen vacancies distributed near the Ti/Ga_2O_3 interface fascinate the tunneling process across the barrier and result in the formation of Ohmic contacts. As a consequence, the serious sub-gap absorption and persistent photoconductivity(PPC) effect degrades the performance of the photoconductive detectors. In contrast, the photovoltaic device with a Schottky contact exhibits an ultra-low dark current less than 1 pA,a high detectivity of 9.82×10^(12) cm·Hz^(1/2)·W^(-1), a fast response time of 243.9 μs, and a high ultraviolet C(UVC)-toultraviolet A(UVA) rejection ratio of 103. The promoting performance is attributed primarily to the reduction of the subgap states and the resultant suppression of PPC effect. With simple architecture, low fabrication cost, and easy fusion with modern high-speed integrated circuitry, these results provide a cost-effective way to realize high performance solar-blind photodetectors towards versatile practical applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.11674405 and 11675280)the Fund from the Laboratory of Microfabrication in Institute of Physics,Chinese Academy of Sciences
文摘In the present work, we explore the solar-blind ultraviolet（UV） photodetectors（PDs） with enhanced photoresponse,fabricated on Ga/Ga2O3 nanocomposite films. Through pre-burying metal Ga layers and thermally post-annealing the laminated Ga2 O3/Ga/Ga2O3 structures, Ga/Ga2O3 nanocomposite films incorporated with Ga nanospheres are obtained. For the prototype PD, it is found that the photocurrent and photoresponsivity will first increase and then decrease monotonically with the thickness of the pre-buried Ga layer increasing. Each of all PDs shows a spectrum response peak at 260 nm, demonstrating the ability to detect solar-blind UV light. Adjustable photoresponse enhancement factors are achieved by means of the surface plasmon in the nanocomposite films. The PD with a 20 nm thick Ga interlayer exhibits the best solar-blind UV photoresponse characteristics with an extremely low dark current of 8.52 p A at 10-V bias, a very high light-to-dark ratio of ～ 8 × 10~5, a large photoresponsivity of 2.85 A/W at 15-V bias, and a maximum enhancement factor of ～ 220. Our research provides a simple and practical route to high performance solar-blind UV PDs and potential applications in the field of optoelectronics.
基金Project supported by National Key Research and Development Plan of China(Grant Nos.2016YFB0400600 and 2016YFB0400601)the National Natural Science Foundation of China(Grant Nos.61574026,11675198,61774072,and 11405017)+2 种基金the Natural Science Foundation of Liaoning Province,China(Grant Nos.201602453 and 201602176)China Postdoctoral Science Foundation Funded Project(Grant No.2016M591434)the Dalian Science and Technology Innovation Fund(Grant No.2018J12GX060)
文摘A solar-blind photodetector is fabricated on single crystal Ga_2O_3 based on vertical structure Schottky barrier diode. A Cu Schottky contact electrode is prepared in a honeycomb porous structure to increase the ultraviolet(UV) transmittance.The quantum efficiency is about 400% at 42 V. The Ga_2O_3 photodetector shows a sharp cutoff wavelength at 259 nm with high solar-blind/visible(= 3213) and solar-blind/UV(= 834) rejection ratio. Time-resolved photoresponse of the photodetector is investigated at 253-nm illumination from room temperature(RT) to 85.8℃. The photodetector maintains a high reversibility and response speed, even at high temperatures.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51572033,61774019,61704153,and 11404029)the Fund from the State Key Laboratory of Information Photonics and Optical Communications(BUPT),Chinathe Fundamental Research Funds for the Central Universities,China
文摘Heterojunctions composed ofβ-Ga2 O3 and ZnO films are fabricated on sapphire substrates by using the laser molecular beam epitaxy method.The heterojunction possesses excellent rectifying characteristics with an asymmetry ratio over 105.Prominent solar-blind photoresponse effect is also observed in the formed heterojunction.The photodetector exhibits a self-powered behavior with a fast response speed(rise time and decay time are 0.035 s and 0.032 s respectively)at zero bias.The obtained high performance can be related to the built-in field driven photogenerated electron-hole separation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51872187,51302174,11774241,and 61704111)the National Key Research and Development Program of China(Grant No.2017YFB0400304)+3 种基金the Natural Science Foundation of Guangdong Province,China(Grant Nos.2016A030313060 and 2017A030310524)the Project of Department of Education of Guangdong Province,China(Grant No.2014KTSCX110)the Fundamental Research Project of Shenzhen,China(Grant No.JCYJ20180206162132006)the Science and Technology Foundation of Shenzhen,China(Grant No.JCYJ2015-2018)
文摘Gallium oxide(Ga_2O_3) thin films were deposited on a-Al2O3(1120) substrates by pulsed laser deposition(PLD) with different oxygen pressures at 650?C. By reducing the oxygen pressure, mixed-phase Ga_2O_3 films with α and β phases can be obtained, and on the basis of this, mixed-phase Ga_2O_3 thin film solar-blind photodetectors(SBPDs) were prepared.Comparing the responsivities of the mixed-phase Ga_2O_3 SBPDs and the single β-Ga_2O_3 SBPDs at a bias voltage of 25 V,it is found that the former has a maximum responsivity of approximately 12 A/W, which is approximately two orders of magnitude larger than that of the latter. This result shows that the mixed-phase structure of Ga_2O_3 thin films can be used to prepare high-responsivity SBPDs. Moreover, the cause of this phenomenon was investigated, which will provide a feasible way to improve the responsivity of Ga_2O_3 thin film SBPDs.
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Project supported by the National Key Reserch and Development Program of China(Grant No.2017YFA0305500)the Fund from Science Technology and Innovation Committee of Shenzhen Municipality,China(Grant No.JCYJ20170307093131123)+6 种基金the National Natural Science Foundation of China(Grant No.61504044)the Key Research and Development Program of Shandong Province,China(Grant Nos.2018GGX101027,2017GGX201002,2017CXGC0412,2016ZDJS09A05,and 2016GGX4101)Shandong Provincial Natural Science Foundation,China(Grant No.ZR2017MF037)"Qilu Young Scholar" Program of Shandong UniversityYantai "13th Five-Year" Marine Economic Innovation and Development Demonstration City Project,China(Grant No.YHCXZB-L-201703)the Union Funds of Guizhou Science and Technology Department and Guizhou Minzu University,China(Grant No.LH20157221)the Fundamental Research Funds of Shandong University,China(Grant Nos.2018WLJH87 and 2017TB0021)
文摘Solar-blind ultraviolet photodetectors have many advantages, such as low false alarm rates, the ability to detect weak signals, and high signal-to-noise ratios. Among the various functional solar-blind ultraviolet photodetectors, Ga-based alloys of AlGaN and Ga_2O_3 are the most commonly adopted channel semiconductor materials and have attracted extensive research attention in the past decades. This review presents an overview of the recent progress in Ga-based solar-blind photodetectors. In case of AlGaN-based solar-blind ultraviolet photodetectors, the response properties can be improved by optimizing the AlN nucleation layer and designing the avalanche structure. On the other hand, we also discuss the morphology and growth methods of Ga_2O_3 nanomaterials and their effect on the performance of the corresponding solarblind photodetectors. The mechanically exfoliated Ga_2O_3 flakes show good potential for ultraviolet detection. Also, Ga_2O_3 nanoflowers and nanowires reveal perfect response to ultraviolet light. Finally, the challenges and future development of Ga-based functional solar-blind ultraviolet photodetectors are summarized.
基金supported by the National Natural Science Foundation of China(Grant No.10974015)the National Defense Pre-Research Foundation of China(Grant No.9140C380502150C38002)
文摘We have developed a superior solar-blind ultraviolet （UV） photocathode with an AlxGa1_xrN photocathode （x ～ 0.45） in semi-transparent mode, and assessed spectra radiant sensitivity related to practical use. Betbre being grown over a basal plane sapphire substrate by low-pressure metal organic chemical vapor deposition （MOCVD）, a reasonable design was made to the photocathode epitaxy structure, focusing on the AlxGa1_xN： Mg active layer, then followed by a comprehen- sive analysis of the structural and optical characterization. The spectra radiant sensitivity is peaked of 41.395 mA/W at wavelength 257 nm and then decreases by about 3 to 4 decades at 400 nm demonstrating the ability of this photocathode for solar-blind application prospects.
基金supported by the National Basic Research Program of China(Grant Nos.2010CB327504,2011CB922100,and 2011CB301900)the National NaturalScience Foundation of China(Grant Nos.60936004 and 11104130)+1 种基金the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK2011556 andBK2011050)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.
