In this article, unique spectral features of short-wave infrared band of 1 μm–3 μm, and various applications related to the photodetectors and focal plane arrays in this band, are introduced briefly. In addition, t...In this article, unique spectral features of short-wave infrared band of 1 μm–3 μm, and various applications related to the photodetectors and focal plane arrays in this band, are introduced briefly. In addition, the different material systems for the devices in this band are outlined. Based on the background, the development of lattice-matched and wavelengthextended InGaAs photodetectors and focal plane arrays, including our continuous efforts in this field, are reviewed. These devices are concentrated on the applications in spectral sensing and imaging, exclusive of optical fiber communication.展开更多
AlN films grown on sputter-deposited and annealed AlN buffer layer by high temperature hydride vapor phase epitaxy(HVPE)have been fabricated and structurally characterized.The crystalline quality and surface morpholog...AlN films grown on sputter-deposited and annealed AlN buffer layer by high temperature hydride vapor phase epitaxy(HVPE)have been fabricated and structurally characterized.The crystalline quality and surface morphology of as-grown AlN films with various V/III ratios were studied and compared.The XRD results showed that the crystalline quality of the AlN film could be optimized when the growth V/III ratio was 150.At the same time,the full width at half-maximum(FWHM)values of(0002)-and(10¯12)-plane were 64 arcsec and 648 arcsec,respectively.As revealed by AFM,the AlN films grown with higher V/III ratios of 150 and 300 exhibited apparent hillock-like surface structure due to the low density of screw threading dislocation(TD).The defects microstructure and strain field around the HVPE-AlN/sputtered-AlN/sapphire interfaces have been investigated by transmission electron microscopy(TEM)technique combined with geometric phase analysis(GPA).It was found that the screw TDs within AlN films intend to turn into loops or half-loops after originating from the AlN/sapphire interface,while the edge ones would bend first and then reacted with others within a region of 400 nm above the interface.Consequently,part of the edge TDs propagated to the surface vertically.The GPA analysis indicated that the voids extending from sapphire to HVPE-AlN layer were beneficial to relax the interfacial strain of the best quality AlN film grown with a V/III ratio of 150.展开更多
The effect of Be doping on the quantum efficiency and the dark current of InAs/GaSb long-wavelength infrared superlattice photodetectors grown by molecular-beam epitaxy on GaSb substrates are reported. A significant i...The effect of Be doping on the quantum efficiency and the dark current of InAs/GaSb long-wavelength infrared superlattice photodetectors grown by molecular-beam epitaxy on GaSb substrates are reported. A significant improvement of quantum efficiency (QE) with p-type doping is demonstrated. Our results show that Be doping level at 2.5 × 10^15 cm^3 gives the highest quantum efficiency of product 28%. We also demonstrate that the increased QE is not only resulted from the longer minority carrier diffusion length, but also the p-n junction location change. Finally, the result also shows that the sample with a doping density of 2,5 × 10^15 cm^3 has the largest D* as 8.68 × 10^10 cm.Hz^l/2.W^-1, which is almost five times D* of the non-intentionally doped one.展开更多
To measure the global atmospheric three-dimensional distribution and change of temperature and humidity is one of the key areas in atmospheric remote sensing detection; it is also a new research and development direct...To measure the global atmospheric three-dimensional distribution and change of temperature and humidity is one of the key areas in atmospheric remote sensing detection; it is also a new research and development direction in the field of meteorological satellite application. As a main element of China second generation of geostationary meteorological satellite Fengyun 4 (FY-4), which was launched on Dec. 11, 2016, the Geostationary Interferometric Infrared Sounder (GIIRS) is the first interferometric infrared sounder working on the international geostationary orbit. It is used for vertical atmospheric sounding and gains atmospheric temperature, humidity, and disturbances. The combination of Fourier transform spectrometer technology and infrared detectors makes GIIRS have high spectral resolution and large coverage over spatial areas. With this kind of instrument, meteoro- logical satellites can improve the capabilities for severe weather event monitoring and numerical weather prediction. Here a concise review of the GIIRS development project, including its history, missions and functions, technical design, key technologies, system integration, calibration and in-orbit operation status, etc., is presented.展开更多
Nowadays, multi-functional materials are desperately required for adapting the complex environment, which urges us to take more factors into consideration. Here, we proposed a broadband microwave absorber with multi-f...Nowadays, multi-functional materials are desperately required for adapting the complex environment, which urges us to take more factors into consideration. Here, we proposed a broadband microwave absorber with multi-functionality such as optically transparent, thermal insulating and soundproof properties. Using indium tin oxide(ITO) based metamaterial, the device can achieve above 90% microwave absorption from 5.6 GHz to 23 GHz(cover X and Ku band). Moreover, with designed vacuum structure inside, the device is thermal insulating and soundproof. These multi-functional advantages give the absorber more flexibility in electromagnetic shielding and stealth application, which can be potentially applied in windows related industry.展开更多
The influence of hydrogenation on the dark current mechanism ofHgCdTe photovoltaic detectors is studied. The hydrogenation is achieved by exposing samples to a H2/Ar plasma atmosphere that was produced during a reacti...The influence of hydrogenation on the dark current mechanism ofHgCdTe photovoltaic detectors is studied. The hydrogenation is achieved by exposing samples to a H2/Ar plasma atmosphere that was produced during a reactive ion etching process. A set of variable-area photomask was specially designed to evaluate the hydrogenation effect. It was found that the current-voltage characteristics were gradually improved when detectors were hydrogenated by different areas. The fitting results of experimental results at reverse bias conditions sustained that the improvement of current-voltage curves was due to the suppression of trap assisted tunneling current and the enhancement of minority lifetime in the depletion region. It was also found that the dominative forward current was gradually converted from a generation-recombination current to a diffusion current with the enlargement of the hydrogenation area, which was infered from the ideality factors by abstraction of forward resistance-voltage curves of different detectors.展开更多
Diffusion bonding is a near net shape forming process that can join dissimilar materials through atomic diffusion under a high pressure at a high temperature.Titanium alloy TC4(Ti-6 Al-4 V)and 4 J29 Kovar alloy(Fe-...Diffusion bonding is a near net shape forming process that can join dissimilar materials through atomic diffusion under a high pressure at a high temperature.Titanium alloy TC4(Ti-6 Al-4 V)and 4 J29 Kovar alloy(Fe-29 Ni-17 Co)were diffusely bonded by a vacuum hot-press sintering process in the temperature range of 700-850°C and bonding time of 120 min,under a pressure of 34.66 MPa.Interfacial microstructures and intermetallic compounds of the diffusion-bonded joints were characterized by optical microscopy,scanning electron microscopy,X-ray diffraction(XRD)and energy dispersive spectroscopy(EDS).The elemental diffusion across the interface was revealed by electron probe microanalysis.Mechanical properties of joints were investigated by micro Vickers hardness and tensile strength.Results of EDS and XRD indicated that(Fe,Co,Ni)-Ti,TiNi,Ti_2Ni,TiNi_2,Fe_2 Ti,Ti_(17) Mn_3 and Al_6 Ti_(19) were formed at the interface.When the bonding temperature was raised from 700 to 850°C,the voids of interface were reduced and intermetallic layers were widened.Maximum tensile strength of joints at 53.5 MPa was recorded by the sintering process at 850°C for 120 min.Fracture surface of the joint indicated brittle nature,and failure took place through interface of intermetallic compounds.Based on the mechanical properties and microstructure of the diffusion-bonded joints,diffusion mechanisms between Ti-6 Al-4 Vtitanium and Fe-29 Ni-17 Co Kovar alloys were analyzed in terms of elemental diffusion,nucleation and growth of grains,plastic deformation and formation of intermetallic compounds near the interface.展开更多
In this paper,we report the growth of Ga As Sb and its crystalline property under various Sb2/As2 flux ratios and growth temperatures.We simulated the incorporation difference between Sb2 and As2 by using a non-equili...In this paper,we report the growth of Ga As Sb and its crystalline property under various Sb2/As2 flux ratios and growth temperatures.We simulated the incorporation difference between Sb2 and As2 by using a non-equilibrium thermodynamic model.Our study of Ga As Sb growth has successfully yielded,high quality In Ga As/Ga As Sb Type II superlattice for which the optical properties were characterized by photoluminescence at different excitation power and temperature.A blue-shift in luminescence peak energy with excitation power was observed and was described by a non-equilibrium carrier density model.We measured and analyzed the dependences of peak energy and integrated intensity on temperature.Two thermal processes were observed from intensity dependent photoluminescence measurements.展开更多
Undoped p-type Ga Sb single crystals were annealed at 550–600℃ for 100 h in ambient antimony. The annealed Ga Sb samples were investigated by Hall effect measurement, glow discharge mass spectroscopy(GDMS), infra...Undoped p-type Ga Sb single crystals were annealed at 550–600℃ for 100 h in ambient antimony. The annealed Ga Sb samples were investigated by Hall effect measurement, glow discharge mass spectroscopy(GDMS), infrared(IR)optical transmission and photoluminescence(PL) spectroscopy. Compared with the as-grown Ga Sb single crystal, the annealed Ga Sb samples have lower hole concentrations and weak native acceptor related PL peaks, indicating the reduction of the concentration of gallium antisite related native acceptor defects. Consequently, the below gap infrared transmission of the Ga Sb samples is enhanced after the thermal treatment. The mechanism about the reduction of the native defect concentration and its influence on the material property were discussed.展开更多
GaSb is the most suitable substrate in the epitaxial growth of mixed semiconductors of GaSb system.In this work,Te-doped GaSb bulk crystals with different doping concentration have been annealed at 550℃ for100 h in a...GaSb is the most suitable substrate in the epitaxial growth of mixed semiconductors of GaSb system.In this work,Te-doped GaSb bulk crystals with different doping concentration have been annealed at 550℃ for100 h in ambient antimony.The annealed samples have been studied by Hall effect measurement,infrared(IR)optical transmission,Glow discharge mass spectroscopy(GDMS) and photoluminescence(PL) spectroscopy.After annealing,Te-doped GaSb samples exhibit a decrease of carrier concentration and increase of mobility,along with an improvement of below gap IR transmission.Native acceptor related electrical compensation analysis suggests a formation of donor defect with deeper energy level.The mechanism of the variation of the defect and its influence on the material properties are discussed.展开更多
A systematic series of silicon (Si) wafer with microstructured anti-reflection film is prepared by femtosec- ond laser pulse. The dependence of the morphology and optical properties of the microstructured Si on the ...A systematic series of silicon (Si) wafer with microstructured anti-reflection film is prepared by femtosec- ond laser pulse. The dependence of the morphology and optical properties of the microstructured Si on the experimental parameters is thoroughly investigated. With the laser pulse duration of 40 fs, central wave- length of 800 nm, repetition rate of 250 kHz, laser pulse power of 300 mW, 250 μm/s scanning speed, and 2 μm of displacement between the parallel scans in the air, the quasiordered arrays of grain microstructures on the Si wafer up to 800-nm tall and 800-nm diameter at the bottom offered near-unity transmission in the mid-infrared wavelength. An anti-reflection film of approximately 3 × 3 (mm) is developed on the (211) Si substrate with the optimized parameters, Moreover, up to 30% improvement of the response performance is demonstrated.展开更多
To suppress the extension of the photo-sensitive area of a planar-type InGaAs detector, the structure of the detector was modified, and the small-diffusion-area diffusion method, circle-type covering contact and guard...To suppress the extension of the photo-sensitive area of a planar-type InGaAs detector, the structure of the detector was modified, and the small-diffusion-area diffusion method, circle-type covering contact and guard-ring were introduced. The laser-beam-induced-current (LBIC) technique was used to study the photo responsive characteristics of the photo-sensitive area of different detector structures. It was indicated that, by modifying the size of the diffusion area, the width of the circle-type covering contact, the distance between the guard-ring and the photo-sensitive area and the working status of the guard-ring, extension of the photo-sensitive area could be effectively suppressed, and the detector photo-sensitive area could be exactly defined.展开更多
The four-probe technique is widely used in the characterization of electrical properties of solids and thin films. To investigate the influence of finite size probes with non-planar contact on the standard four-probe ...The four-probe technique is widely used in the characterization of electrical properties of solids and thin films. To investigate the influence of finite size probes with non-planar contact on the standard four-probe method, we have proposed an image method to simulate the potential distribution within the specimen. The numerical results show that for infinitely thick samples, the standard method can only provide accurate determination of resistivity (relative error below 1%) when the ratio of the average inter-electrode spacing to the diameter of the probe is greater than 3. We have also found that disregarding the probe size brings a less dominate error than that introduced by the approximate formula, when the sample's thickness is close to the inter-electrode spacing.展开更多
Oxygen-containing defects are very important for altering the nonlinear optical (NLO) properties of graphene. To investigate the correlation between oxygen-containing defects and the synergistic NLO response in graphe...Oxygen-containing defects are very important for altering the nonlinear optical (NLO) properties of graphene. To investigate the correlation between oxygen-containing defects and the synergistic NLO response in graphenebased nanocomposites, we attached CdS nanocrystals on the surface of graphene (G) and prepared G/CdS nanohybrids (NHs) consisting of various oxygen-containing functional groups via a chemical method. The NLO absorption and refraction of G/CdS NHs under single pulse laser irradiation are enhanced by 10.8 times with the concentration decrease of surface oxygen-containing groups, which might be attributed to the local field effects and synergetic effects stemming from charge transfer between the two components. However, the optical nonlinearity is decreased with further concentration decrease, which might arise from sp^2 fragment interconnection and surface defects in the NHs. The NLO absorption transformation from two-photon absorption to saturable absorption with oxygen decrease is observed, and intensity-related NLO absorption and refraction in NHs are also discussed. Meanwhile, the G/CdS NHs exhibit superior NLO properties, implying potential applications of NH material in NLO devices.展开更多
Linearly graded In_xGa_(1-x)As metamorphic buffers with different mismatch grading rates were grown on InP substrate by gas source molecular beam epitaxy.Room temperature photoluminescence spectra show that the samp...Linearly graded In_xGa_(1-x)As metamorphic buffers with different mismatch grading rates were grown on InP substrate by gas source molecular beam epitaxy.Room temperature photoluminescence spectra show that the sample with lower mismatch grading rate in the buffer has stronger photoluminescence signal,indicating the improved optical property.Atomic force microscope images show that the lower mismatch grading rate in the buffer leads to a slightly rougher surface.The relaxation procedure with two steps in the buffer layers has been observed by X-ray diffraction reciprocal space mapping.The measurements of X-ray diffraction also reveal that the lower mismatch grading rate in the buffer is beneficial for the lattice relaxation and release of residual strain.To further increase the relaxation degree,a lower mismatch grading rate and composition "overshoot" are suggested.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0402400)the National Natural Science Foundation of China(Grant Nos.61675225,61605232,and 61775228)the Shanghai Rising-Star Program,China(Grant No.17QA1404900)
文摘In this article, unique spectral features of short-wave infrared band of 1 μm–3 μm, and various applications related to the photodetectors and focal plane arrays in this band, are introduced briefly. In addition, the different material systems for the devices in this band are outlined. Based on the background, the development of lattice-matched and wavelengthextended InGaAs photodetectors and focal plane arrays, including our continuous efforts in this field, are reviewed. These devices are concentrated on the applications in spectral sensing and imaging, exclusive of optical fiber communication.
基金Project supported by the National Key Technologies R&D Program of China(Grant No.2017YFB0404100)Key Laboratory of Infrared Imaging Materials and Detectors,Shanghai Institute of Technical Physics,Chinese Academy of Sciences.
文摘AlN films grown on sputter-deposited and annealed AlN buffer layer by high temperature hydride vapor phase epitaxy(HVPE)have been fabricated and structurally characterized.The crystalline quality and surface morphology of as-grown AlN films with various V/III ratios were studied and compared.The XRD results showed that the crystalline quality of the AlN film could be optimized when the growth V/III ratio was 150.At the same time,the full width at half-maximum(FWHM)values of(0002)-and(10¯12)-plane were 64 arcsec and 648 arcsec,respectively.As revealed by AFM,the AlN films grown with higher V/III ratios of 150 and 300 exhibited apparent hillock-like surface structure due to the low density of screw threading dislocation(TD).The defects microstructure and strain field around the HVPE-AlN/sputtered-AlN/sapphire interfaces have been investigated by transmission electron microscopy(TEM)technique combined with geometric phase analysis(GPA).It was found that the screw TDs within AlN films intend to turn into loops or half-loops after originating from the AlN/sapphire interface,while the edge ones would bend first and then reacted with others within a region of 400 nm above the interface.Consequently,part of the edge TDs propagated to the surface vertically.The GPA analysis indicated that the voids extending from sapphire to HVPE-AlN layer were beneficial to relax the interfacial strain of the best quality AlN film grown with a V/III ratio of 150.
基金Supported by the National Natural Science Foundation of China under Grant No 61176082, and the Natural Science Foundation of Shanghai under Grand No 13ZR1463800.
文摘The effect of Be doping on the quantum efficiency and the dark current of InAs/GaSb long-wavelength infrared superlattice photodetectors grown by molecular-beam epitaxy on GaSb substrates are reported. A significant improvement of quantum efficiency (QE) with p-type doping is demonstrated. Our results show that Be doping level at 2.5 × 10^15 cm^3 gives the highest quantum efficiency of product 28%. We also demonstrate that the increased QE is not only resulted from the longer minority carrier diffusion length, but also the p-n junction location change. Finally, the result also shows that the sample with a doping density of 2,5 × 10^15 cm^3 has the largest D* as 8.68 × 10^10 cm.Hz^l/2.W^-1, which is almost five times D* of the non-intentionally doped one.
基金supported by the China’s National Key Special Earth Observation and Navigation Project,Ministry of Science and Technology of China(MOST)(No.2016YFB0500600)
文摘To measure the global atmospheric three-dimensional distribution and change of temperature and humidity is one of the key areas in atmospheric remote sensing detection; it is also a new research and development direction in the field of meteorological satellite application. As a main element of China second generation of geostationary meteorological satellite Fengyun 4 (FY-4), which was launched on Dec. 11, 2016, the Geostationary Interferometric Infrared Sounder (GIIRS) is the first interferometric infrared sounder working on the international geostationary orbit. It is used for vertical atmospheric sounding and gains atmospheric temperature, humidity, and disturbances. The combination of Fourier transform spectrometer technology and infrared detectors makes GIIRS have high spectral resolution and large coverage over spatial areas. With this kind of instrument, meteoro- logical satellites can improve the capabilities for severe weather event monitoring and numerical weather prediction. Here a concise review of the GIIRS development project, including its history, missions and functions, technical design, key technologies, system integration, calibration and in-orbit operation status, etc., is presented.
基金This work has been supported by the Open Research Funding from Key Laboratory of Infrared Imaging Materials and Detectors(Shanghai Institute of Technical Physics,Chinese Academy of Sciences)。
文摘Nowadays, multi-functional materials are desperately required for adapting the complex environment, which urges us to take more factors into consideration. Here, we proposed a broadband microwave absorber with multi-functionality such as optically transparent, thermal insulating and soundproof properties. Using indium tin oxide(ITO) based metamaterial, the device can achieve above 90% microwave absorption from 5.6 GHz to 23 GHz(cover X and Ku band). Moreover, with designed vacuum structure inside, the device is thermal insulating and soundproof. These multi-functional advantages give the absorber more flexibility in electromagnetic shielding and stealth application, which can be potentially applied in windows related industry.
文摘The influence of hydrogenation on the dark current mechanism ofHgCdTe photovoltaic detectors is studied. The hydrogenation is achieved by exposing samples to a H2/Ar plasma atmosphere that was produced during a reactive ion etching process. A set of variable-area photomask was specially designed to evaluate the hydrogenation effect. It was found that the current-voltage characteristics were gradually improved when detectors were hydrogenated by different areas. The fitting results of experimental results at reverse bias conditions sustained that the improvement of current-voltage curves was due to the suppression of trap assisted tunneling current and the enhancement of minority lifetime in the depletion region. It was also found that the dominative forward current was gradually converted from a generation-recombination current to a diffusion current with the enlargement of the hydrogenation area, which was infered from the ideality factors by abstraction of forward resistance-voltage curves of different detectors.
基金supported by National Natural Science Foundation of China(No.51201143)Fundamental Research Funds for the Central Universities (No.2682015CX001)+5 种基金China Postdoctoral Science Foundation(No.2015M570794)Key Laboratory of Infrared Imaging Materials and Detectors,Shanghai Institute of Technical Physics,Chinese Academy of Sciences(No.IIMDKFJJ-14-04)Sichuan Science and Technology Support Program(No.2016FZ0079)R&D Projects Funding from the Research Council of Norway(No.263875/H30)supported by the U.S. National Science Foundation No.1436120supported by DoD W911NF14-1-0060
文摘Diffusion bonding is a near net shape forming process that can join dissimilar materials through atomic diffusion under a high pressure at a high temperature.Titanium alloy TC4(Ti-6 Al-4 V)and 4 J29 Kovar alloy(Fe-29 Ni-17 Co)were diffusely bonded by a vacuum hot-press sintering process in the temperature range of 700-850°C and bonding time of 120 min,under a pressure of 34.66 MPa.Interfacial microstructures and intermetallic compounds of the diffusion-bonded joints were characterized by optical microscopy,scanning electron microscopy,X-ray diffraction(XRD)and energy dispersive spectroscopy(EDS).The elemental diffusion across the interface was revealed by electron probe microanalysis.Mechanical properties of joints were investigated by micro Vickers hardness and tensile strength.Results of EDS and XRD indicated that(Fe,Co,Ni)-Ti,TiNi,Ti_2Ni,TiNi_2,Fe_2 Ti,Ti_(17) Mn_3 and Al_6 Ti_(19) were formed at the interface.When the bonding temperature was raised from 700 to 850°C,the voids of interface were reduced and intermetallic layers were widened.Maximum tensile strength of joints at 53.5 MPa was recorded by the sintering process at 850°C for 120 min.Fracture surface of the joint indicated brittle nature,and failure took place through interface of intermetallic compounds.Based on the mechanical properties and microstructure of the diffusion-bonded joints,diffusion mechanisms between Ti-6 Al-4 Vtitanium and Fe-29 Ni-17 Co Kovar alloys were analyzed in terms of elemental diffusion,nucleation and growth of grains,plastic deformation and formation of intermetallic compounds near the interface.
基金supported by the National Natural Science Foundation of China(Grant No.61176082)the National Basic Research Program of China(Grant No.2012CB619203)
文摘In this paper,we report the growth of Ga As Sb and its crystalline property under various Sb2/As2 flux ratios and growth temperatures.We simulated the incorporation difference between Sb2 and As2 by using a non-equilibrium thermodynamic model.Our study of Ga As Sb growth has successfully yielded,high quality In Ga As/Ga As Sb Type II superlattice for which the optical properties were characterized by photoluminescence at different excitation power and temperature.A blue-shift in luminescence peak energy with excitation power was observed and was described by a non-equilibrium carrier density model.We measured and analyzed the dependences of peak energy and integrated intensity on temperature.Two thermal processes were observed from intensity dependent photoluminescence measurements.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61474104 and 61504131)
文摘Undoped p-type Ga Sb single crystals were annealed at 550–600℃ for 100 h in ambient antimony. The annealed Ga Sb samples were investigated by Hall effect measurement, glow discharge mass spectroscopy(GDMS), infrared(IR)optical transmission and photoluminescence(PL) spectroscopy. Compared with the as-grown Ga Sb single crystal, the annealed Ga Sb samples have lower hole concentrations and weak native acceptor related PL peaks, indicating the reduction of the concentration of gallium antisite related native acceptor defects. Consequently, the below gap infrared transmission of the Ga Sb samples is enhanced after the thermal treatment. The mechanism about the reduction of the native defect concentration and its influence on the material property were discussed.
基金Project supported by the National Natural Science Foundation of China(Nos.61474104,61504131)
文摘GaSb is the most suitable substrate in the epitaxial growth of mixed semiconductors of GaSb system.In this work,Te-doped GaSb bulk crystals with different doping concentration have been annealed at 550℃ for100 h in ambient antimony.The annealed samples have been studied by Hall effect measurement,infrared(IR)optical transmission,Glow discharge mass spectroscopy(GDMS) and photoluminescence(PL) spectroscopy.After annealing,Te-doped GaSb samples exhibit a decrease of carrier concentration and increase of mobility,along with an improvement of below gap IR transmission.Native acceptor related electrical compensation analysis suggests a formation of donor defect with deeper energy level.The mechanism of the variation of the defect and its influence on the material properties are discussed.
基金supported by the Opening foundationof Key Laboratory of Infrared Imaging Material and Detectors,Shanghai Institute of Technical Physics,CAS
文摘A systematic series of silicon (Si) wafer with microstructured anti-reflection film is prepared by femtosec- ond laser pulse. The dependence of the morphology and optical properties of the microstructured Si on the experimental parameters is thoroughly investigated. With the laser pulse duration of 40 fs, central wave- length of 800 nm, repetition rate of 250 kHz, laser pulse power of 300 mW, 250 μm/s scanning speed, and 2 μm of displacement between the parallel scans in the air, the quasiordered arrays of grain microstructures on the Si wafer up to 800-nm tall and 800-nm diameter at the bottom offered near-unity transmission in the mid-infrared wavelength. An anti-reflection film of approximately 3 × 3 (mm) is developed on the (211) Si substrate with the optimized parameters, Moreover, up to 30% improvement of the response performance is demonstrated.
基金supported by the Key Program ofthe National Natural Science Foundation of China(No.5063206)the Knowledge Innovation Program of the Chinese Academy of Sciences(Nos.C2-32,C2-50).
文摘To suppress the extension of the photo-sensitive area of a planar-type InGaAs detector, the structure of the detector was modified, and the small-diffusion-area diffusion method, circle-type covering contact and guard-ring were introduced. The laser-beam-induced-current (LBIC) technique was used to study the photo responsive characteristics of the photo-sensitive area of different detector structures. It was indicated that, by modifying the size of the diffusion area, the width of the circle-type covering contact, the distance between the guard-ring and the photo-sensitive area and the working status of the guard-ring, extension of the photo-sensitive area could be effectively suppressed, and the detector photo-sensitive area could be exactly defined.
基金Project supported by the Innovation Project of the Shanghai Institute of Technical Physics,CAS(No.CXJJ-Q-DX-57)
文摘The four-probe technique is widely used in the characterization of electrical properties of solids and thin films. To investigate the influence of finite size probes with non-planar contact on the standard four-probe method, we have proposed an image method to simulate the potential distribution within the specimen. The numerical results show that for infinitely thick samples, the standard method can only provide accurate determination of resistivity (relative error below 1%) when the ratio of the average inter-electrode spacing to the diameter of the probe is greater than 3. We have also found that disregarding the probe size brings a less dominate error than that introduced by the approximate formula, when the sample's thickness is close to the inter-electrode spacing.
基金National Natural Science Foundation of China (NSFC) (61404045,U1404624,61875053)Natural ScienceFoundation of Henan Province (144300510018)Scientific Research Funds of Henan University (CX0000A40680)
文摘Oxygen-containing defects are very important for altering the nonlinear optical (NLO) properties of graphene. To investigate the correlation between oxygen-containing defects and the synergistic NLO response in graphenebased nanocomposites, we attached CdS nanocrystals on the surface of graphene (G) and prepared G/CdS nanohybrids (NHs) consisting of various oxygen-containing functional groups via a chemical method. The NLO absorption and refraction of G/CdS NHs under single pulse laser irradiation are enhanced by 10.8 times with the concentration decrease of surface oxygen-containing groups, which might be attributed to the local field effects and synergetic effects stemming from charge transfer between the two components. However, the optical nonlinearity is decreased with further concentration decrease, which might arise from sp^2 fragment interconnection and surface defects in the NHs. The NLO absorption transformation from two-photon absorption to saturable absorption with oxygen decrease is observed, and intensity-related NLO absorption and refraction in NHs are also discussed. Meanwhile, the G/CdS NHs exhibit superior NLO properties, implying potential applications of NH material in NLO devices.
基金Project supported by the National Basic Research Program of China(No.2012CB619202)the National Natural Science Foundation of China(Nos.61275113,61204133)the Founding of CAS Key Laboratory of Infrared Imaging Materials and Detectors
文摘Linearly graded In_xGa_(1-x)As metamorphic buffers with different mismatch grading rates were grown on InP substrate by gas source molecular beam epitaxy.Room temperature photoluminescence spectra show that the sample with lower mismatch grading rate in the buffer has stronger photoluminescence signal,indicating the improved optical property.Atomic force microscope images show that the lower mismatch grading rate in the buffer leads to a slightly rougher surface.The relaxation procedure with two steps in the buffer layers has been observed by X-ray diffraction reciprocal space mapping.The measurements of X-ray diffraction also reveal that the lower mismatch grading rate in the buffer is beneficial for the lattice relaxation and release of residual strain.To further increase the relaxation degree,a lower mismatch grading rate and composition "overshoot" are suggested.