The peculiar photoconduction in semi insulating GaAs photoconductive switch being triggered by 1064nm laser pulse is reported.The gap between two electrodes of the switch is 4mm.When it is triggered by laser pulse wi...The peculiar photoconduction in semi insulating GaAs photoconductive switch being triggered by 1064nm laser pulse is reported.The gap between two electrodes of the switch is 4mm.When it is triggered by laser pulse with energy of 0 8mJ and the pulse width of 5ns,and operated at biased electric field of 2 0 and 6 0kV/cm,both linear and nonlinear modes of the switch are observed respectively.Whereas the biased electric field adds to 9 5kV/cm,and the triggered laser is in range of 0 5～1 0mJ,the peculiar performed characteristic is observed:the switch gives a linear waveform firstly,and then after a delay time of about 20～250ns,it outputs a nonlinear waveform again.The physical mechanism of this specific phenomenon is associated with the anti site defects of semi insulating GaAs and two step single photon absorption.The delay time between linear waveform and nonlinear waveform is calculated,and the result matches the experiments.展开更多
A mode for the periodicity and weakening surge in semi-insulating GaAs photoconductive semiconductor switches is proposed based on the transferred-electron effect. It is shown that the periodicity and weakening surge ...A mode for the periodicity and weakening surge in semi-insulating GaAs photoconductive semiconductor switches is proposed based on the transferred-electron effect. It is shown that the periodicity and weakening surge is caused by the interaction between the self-excitation of the resonant circuit and transferred electron oscillation of the switch. The bias electric field （larger than Gunn threshold） across the switch is modulated by the AC elec-tric field,when the instantaneous bias electric field E is swinging below Gunn electric field threshold ET but grea-ter than the sustaining field Es （the minimum electric field required to support the domain） at the time of the do-main reaching the anode, and then the delayed-dipole domain mode of switch is obtained. It is the photon-activated carriers that satisfy the requirement of charge domain formation on carrier concentration and device length prod-uct of 10^12 cm^-2,and the semi-insulating GaAs photoconductive semiconductor switch is essentially a type of pho-ton-activated charge domain device.展开更多
A model is presented to describe a compensation mechanism for semi-insulating 6H-SiC grown with the intentional doping of vanadium. Because we found nitrogen to be the principal shallow donor impurity in SiC by second...A model is presented to describe a compensation mechanism for semi-insulating 6H-SiC grown with the intentional doping of vanadium. Because we found nitrogen to be the principal shallow donor impurity in SiC by secondary ion mass spectroscopy （SIMS） measurements, semi-insulating properties in SiC are achieved by compensating the nitrogen donor with the vanadium deep acceptor level. The presence of different vanadium charge states V^3＋ and V^4＋ is detected by electron paramagnetic resonance and optical absorption measurements,which coincides with the results obtained by SIMS measurements. Both optical absorption and low temperature photoluminescence measurements reveal that the vanadium acceptor level is located at 0.62eV below the conduction band in 6H-SiC.展开更多
One-port surface acoustic wave resonators(SAWRs) are fabricated on semi-insulating high-quality bulk GaN and GaN film substrates, respectively. The semi-insulating GaN substrates are grown by hydride vapor phase epita...One-port surface acoustic wave resonators(SAWRs) are fabricated on semi-insulating high-quality bulk GaN and GaN film substrates, respectively. The semi-insulating GaN substrates are grown by hydride vapor phase epitaxy(HVPE)and doped with Fe. The anisotropy of Rayleigh propagation and the electromechanical coupling coefficient in Fe-doped GaN are investigated. The difference in resonance frequency between the SAWs between [1120] GaN and [1100] GaN is about 0.25% for the Rayleigh propagation mode, which is smaller than that of non-intentionally doped GaN film(~1%)reported in the literature. The electromechanical coupling coefficient of Fe-doped GaN is about 3.03%, which is higher than that of non-intentionally doped GaN film. The one-port SAWR fabricated on an 8-μm Fe-doped GaN/sapphire substrate has a quality factor of 2050, and that fabricated on Fe-doped bulk GaN has a quality factor as high as 3650. All of our results indicate that high-quality bulk GaN is a very promising material for application in SAW devices.展开更多
Two-inch semi-insulating SiC bulk crystals with resistivity higher than 1 × 10^6 Qcm were achieved by vanadium doping during sublimation. Secondary-ion-mass-spectrometry （SIMS） was employed to determine the con...Two-inch semi-insulating SiC bulk crystals with resistivity higher than 1 × 10^6 Qcm were achieved by vanadium doping during sublimation. Secondary-ion-mass-spectrometry （SIMS） was employed to determine the concentration of impurities in the crystals, such as B, AI, V and N. These results indicated that the concentration of nitrogen and aluminum kept on decreasing and the concentration of B and V was almost constant during the whole growth. An inner crucible was used to control the exhausting of vanadium, which made the uniformity of the high resistivity （〉1×10^6 Ωcm） in the wafer up to 80%. High-performance AlGaN/GaN high-electronmobility-transistor （HEMT） materials and devices were grown and fabricated on semi-insulating 6H-SiC sub- strates. The two-dimensional electron gas （2DEG） mobility at room-temperature was 1795 cm^2/V-s. The charge carrier concentration of the substrate determined by capacitance-voltage （C-V） test was 7.3×10^15 cm^-3. The device with a gate width of I mm exhibits a maximum output power of 5.5 W at 8 GHz, which proves the semi-insulating property of the substrates indirectly.展开更多
Properties of Fe-doped semi-insulating (SI) InP with different iron concentrations are studied by using Hall effect,current-voltage ( I-V ),photoluminescence spectroscopy (PL) and photocurrent spectroscopy(PC)measurem...Properties of Fe-doped semi-insulating (SI) InP with different iron concentrations are studied by using Hall effect,current-voltage ( I-V ),photoluminescence spectroscopy (PL) and photocurrent spectroscopy(PC)measurements. I-V characteristics of SI InP strongly depend on Fe doping concentration.Fe doping concentration also influences optical properties and defective formation in as-grown SI InP.Band-gap narrowing phenomenon and defects in Fe doped SI InP are studied using PL and PC.展开更多
Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Exper...Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Experimental results indicate that, after an annealing at 950 degreesC for 14 h under low As pressure, the Hall mobility decreases and the resistivity increases dramatically for the samples. These changes in electrical properties are due to the generation of intrinsic acceptor defects, and the generation of the intrinsic acceptor defects originates from the outdiffusion of As interstitial at high temperature. The generation of the intrinsic defects and these changes in electrical properties can be suppressed by increasing the applied As pressure during annealing. The concentration of the main donor defect E12 (AsGaVGa) can be decreased by about one order of magnitude by an evacuated annealing at 1120 degreesC for 2-8 h followed by a fast cooling. The decrease in E12 concentration can also be suppressed by increasing the As pressure during annealing.展开更多
We demonstrate high-performance In0.23 Ga0.77 As channel metal-oxide-semiconductor field-effect transistors （ MOS- FETs） with high on-current to off-current （Ion/Ioff） ratio grown on semi-insulating GaAs wafers by...We demonstrate high-performance In0.23 Ga0.77 As channel metal-oxide-semiconductor field-effect transistors （ MOS- FETs） with high on-current to off-current （Ion/Ioff） ratio grown on semi-insulating GaAs wafers by metal-organic chemical vapor deposition （MOCVD）. The 2μm channel-length devices exhibit a peak extrinsic transeonductance of 150 mS/mm and a drain current up to 500 mA/mm. The maximum effective mobility is 1680 cm2/Vs extracted by the split C-V method. Furthermore, the Ion/Ioff ratio is significantly improved from approximately 4.5 × 10^3 up to approximately 4.32 × 10^4 by controlling the etch thickness of In0.49Ga0.51P, The high drain current and high Ion/Ioff ratio of the In0.23Ga0.77As channel MOSFETs are achieved due to the high effective mobility and the low gate leakage current density.展开更多
Based on the theoretical analysis of the 4H-SiC Schottky-barrier diodes （SBDs） with field plate termination, 4H-SiC SBD with semi-insulating polycrystalline silicon （SIPOS） FP termination has been fabricated. The ...Based on the theoretical analysis of the 4H-SiC Schottky-barrier diodes （SBDs） with field plate termination, 4H-SiC SBD with semi-insulating polycrystalline silicon （SIPOS） FP termination has been fabricated. The relative dielectric con-stant of the SIPOS dielectric first used in 4H-SiC devices is 10.4, which is much higher than that of the SiO2 dielectric, leading to benefitting the performance of devices. The breakdown voltage of the fabricated SBD could reach 1200 V at leak-age current 20 μA, about 70% of the theoretical breakdown voltage. Meanwhile, both of the simulation and experimental results show that the length of the SIPOS FP termination is an important factor for structure design.展开更多
The microprecipitates in the as-grown undoped and In-doped semi-insulating GaAs single crystals have been ex- amined by JEM 200 CX transmission electron microscope.The microprecipitates consist of GaAs polycrystalline...The microprecipitates in the as-grown undoped and In-doped semi-insulating GaAs single crystals have been ex- amined by JEM 200 CX transmission electron microscope.The microprecipitates consist of GaAs polycrystalline grains of 5～100nm in size have been evidenced in dislocated crystals.Energy dispersive X-ray analysis shows that the mieropreeipitates are predominately arsenic-rich GaAs.The As/Ga atomic ratio of the microprecipitates in In-doped crystal is higher than that of undoped crystal.It is suggested that the formation of the microprecipitates may be induced by the local fluctuation of compositional undercooling during crystal growth.展开更多
Metal-semiconductor-metal photodetectors on semi-insulating Ga As with interdigital electrodes showed significant enhancement in the spectral response in the near-infrared region as the electrode spacing is reduced. T...Metal-semiconductor-metal photodetectors on semi-insulating Ga As with interdigital electrodes showed significant enhancement in the spectral response in the near-infrared region as the electrode spacing is reduced. The photocurrent for the device with 5 μm interdigital spacing is five orders of magnitude higher than the dark current, and the room temperature detectivity is on the order of 2.4 × 1012cm Hz1∕2W-1at 5 V bias. Furthermore,the spectral response of this device possesses strong dependence on the polarization of incident light showing potential plasmonic effects with only microscale dimensions. These experimental data were analyzed using optical simulation to confirm the response of the devices.展开更多
The intrinsic defects in epitaxial semi-insulating 4H-SiC prepared by low pressure chemical vapor deposition （LPCVD） are studied by electron spin resonance （ESR） with different illumination times. The results show...The intrinsic defects in epitaxial semi-insulating 4H-SiC prepared by low pressure chemical vapor deposition （LPCVD） are studied by electron spin resonance （ESR） with different illumination times. The results show that the intrinsic defects in as-grown 4H-SiC consist of carbon vacancy （Vc） and complex-compounds-related Vc. There are two other apexes presented in the ESR spectra after illumination by Xe light, which are likely to be Vsi and VcCsi. Illumination time changes the relative density of intrinsic defects in 4H-SiC; the relative density of intrinsic defects reaches a maximum when the illumination time is 2.5 min, and the ratio of Vc to complex compounds is minimized simultaneously. It can be deduced that some Vsi may be transformed to the complex-compounds-related Vc because of the illumination.展开更多
A comprehensive analysis of multi-quantum-well electroabsorption modulators buried with semi-insulating (SI)-InP is presented. We quantitatively demonstrate that suppression of Zn diffusion into the burying and optica...A comprehensive analysis of multi-quantum-well electroabsorption modulators buried with semi-insulating (SI)-InP is presented. We quantitatively demonstrate that suppression of Zn diffusion into the burying and optical core layers plays a key role in high-speed and high-extinction operation.展开更多
OaAs has been widely used to fabricate a variety of optoelectronic devices by virtue of its superior performance, and it is very important to accurately measure its electrical and optical properties. In this study, a ...OaAs has been widely used to fabricate a variety of optoelectronic devices by virtue of its superior performance, and it is very important to accurately measure its electrical and optical properties. In this study, a semi- insulation （SI） GaAs wafer is investigated by the terahertz （THz） non-destructive testing technology. Using an air biased coherent generation and detection THz time domain spectroscopy system, the THz time domain waveform and spectrum of SI-GaAs are obtained by the time domain spectroscopy module, and its optical- electrical characteristics including complex refractive index, permittivity and dielectric loss angle are calculated. Its carrier lifetime is measured by the optical-pump THz-probe module, and the THz pulse induced intervalley scattering in photo-excited SI-GaAs is discussed.展开更多
The free electron concentration of as-grown liquid encapsulated Czochralski (LE C) InP measured by Hall effect is much higher than the concentration of net dono r impurity determined by glow discharge mass spectroscop...The free electron concentration of as-grown liquid encapsulated Czochralski (LE C) InP measured by Hall effect is much higher than the concentration of net dono r impurity determined by glow discharge mass spectroscopy.Evidence of the existe nce of a native donor hydrogen-indium vacancy complex in LEC undoped and Fe-do ped InP materials can be obseved with infrared absorption spectra.The concentra tion increase of the donor complex correlates with the increase of ionized deep acceptor iron impurity Fe concentration in Fe-doped semi-insulating (S I) InP.These results indicate that the hydrogen-indium vacancy complex is an im portant donor defect in as-grown LEC InP,and that it has significant influence on the compensation in Fe-doped SI InP展开更多
Gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS's) with a 1.55mm gap spacing trigged by 1553nm femtosecond fiber laser pulse is presented.The switches are biased with 3.33～10.3kV/cm and irrad...Gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS's) with a 1.55mm gap spacing trigged by 1553nm femtosecond fiber laser pulse is presented.The switches are biased with 3.33～10.3kV/cm and irradiated by femtosecond fiber laser operated at a wavelength of 1553nm with pulse width of 200fs and pulse energy of 0.2nJ.The experiments show that,even if the semi-insulating GaAs photoconductive switch operates under the electrical field of 10.3kV/cm,it will be still linear response,and a clear corresponding output electric pulse with the peak voltage of 0.8mV is captured.From the weak photoconductivity on laser intensity,photoabsorption mediated by EL2 deep level defects is suggested,as the primary process for the photoconductivity.展开更多
The diffusion behavior of vanadium （V） implanted in SiC is investigated by secondary ion mass spec- trometry. Significant redistribution, especially out-diffusion of vanadium towards the sample surface, is not ob- s...The diffusion behavior of vanadium （V） implanted in SiC is investigated by secondary ion mass spec- trometry. Significant redistribution, especially out-diffusion of vanadium towards the sample surface, is not ob- served after 1650℃ annealing. Higher carrier concentration is obtained due to a lack of compensation of vanadium in the surface region. The electrical characteristics of Ni contacts to V-implanted n-type 4H-SiC are investigated using a linear transmission line method. A specific contact resistance as low as 4.4 × 10^-3Ω · cmA^2 is achieved after annealing at 1050℃ for 10min in gas ambient consisting of 90% N2 and 10% H2 X-ray diffraction analysis shows the formation of Ni2 Si and graphite phase at the interface after annealing. This provides the evidence that the car- bon vacancies,resulting from the out-diffusion of carbon atoms from SiC, contribute to the formation of ohmic contact through the reduction of effective Schottky barrier height for the transport of electrons.展开更多
A semi-insulating layer is obtained in n-type 4H-SiC by vanadium-ion implantation. A little higher resistivity is obtained by increasing the annealing temperature from 1450 to 1650 ℃. The resistivity at room temperat...A semi-insulating layer is obtained in n-type 4H-SiC by vanadium-ion implantation. A little higher resistivity is obtained by increasing the annealing temperature from 1450 to 1650 ℃. The resistivity at room temperature is as high as 7.6 ×10^6 Ω. cm. Significant redistribution of vanadium is not observed even after 1650 ℃ annealing. Temperaturedependent resistivity and optical absorption of V-implanted samples are measured. The activation energy of vanadium acceptor level is observed to be at about Ec - 1.1 eV.展开更多
This paper describes an experimental and theoretical study on an extraction phenomenon of liquids occurring at an air gap between the liquid surface and the electrode by applying a direct current (DC) or low-frequency...This paper describes an experimental and theoretical study on an extraction phenomenon of liquids occurring at an air gap between the liquid surface and the electrode by applying a direct current (DC) or low-frequency alternating current (AC) voltage. Three liquids with a different physical property;2,3-dihydrodecafluoropenten, palm fatty acid ester oil and crude rapeseed oil are used as working liquids. The electrode configuration is the sphere or plane (high voltage electrode) to grounded plane electrode. The grounded plane electrode is fixed to the bottom of the test vessel with working liquid and the high voltage electrode is installed in an air above the liquid surface against the grounded plane electrode. The liquid surface swells towards the high voltage electrode by the increase of voltage and the liquid is extracted in a short time, thereafter the air gap between the liquid surface and the high voltage electrode is bridged at a thick liquid column. Such the liquid behavior displays unique features with voltage polarity effect for each working liquid. The relationship between the applied voltage, current variation, height of swollen liquid, force pulling liquid and dynamic feature of liquid is examined experimentally. The liquid behavior is considered theoretically based on experimental observations.展开更多
A new semi-insulation structure in which one isolated island is connected to the substrate was pro- posed. Based on this semi-insulation structure, an advanced BCD technology which can integrate a vertical de- vice wi...A new semi-insulation structure in which one isolated island is connected to the substrate was pro- posed. Based on this semi-insulation structure, an advanced BCD technology which can integrate a vertical de- vice without extra internal interconnection structure was presented. The manufacturing of the new semi-insulation structure employed multi-epitaxy and selectively multi-doping. Isolated islands are insulated with the substrate by reverse-biased PN junctions. Adjacent isolated islands are insulated by isolation wall or deep dielectric trenches. The proposed semi-insulation structure and devices fixed in it were simulated through two-dimensional numerical computer simulators. Based on the new BCD technology, a smart power integrated circuit was designed and fabri- cated. The simulated and tested results of Vertical DMOS, MOSFETs, BJTs, resistors and diodes indicated that the proposed semi-insulation structure is reasonable and the advanced BCD technology is validated.展开更多
文摘The peculiar photoconduction in semi insulating GaAs photoconductive switch being triggered by 1064nm laser pulse is reported.The gap between two electrodes of the switch is 4mm.When it is triggered by laser pulse with energy of 0 8mJ and the pulse width of 5ns,and operated at biased electric field of 2 0 and 6 0kV/cm,both linear and nonlinear modes of the switch are observed respectively.Whereas the biased electric field adds to 9 5kV/cm,and the triggered laser is in range of 0 5～1 0mJ,the peculiar performed characteristic is observed:the switch gives a linear waveform firstly,and then after a delay time of about 20～250ns,it outputs a nonlinear waveform again.The physical mechanism of this specific phenomenon is associated with the anti site defects of semi insulating GaAs and two step single photon absorption.The delay time between linear waveform and nonlinear waveform is calculated,and the result matches the experiments.
文摘A mode for the periodicity and weakening surge in semi-insulating GaAs photoconductive semiconductor switches is proposed based on the transferred-electron effect. It is shown that the periodicity and weakening surge is caused by the interaction between the self-excitation of the resonant circuit and transferred electron oscillation of the switch. The bias electric field （larger than Gunn threshold） across the switch is modulated by the AC elec-tric field,when the instantaneous bias electric field E is swinging below Gunn electric field threshold ET but grea-ter than the sustaining field Es （the minimum electric field required to support the domain） at the time of the do-main reaching the anode, and then the delayed-dipole domain mode of switch is obtained. It is the photon-activated carriers that satisfy the requirement of charge domain formation on carrier concentration and device length prod-uct of 10^12 cm^-2,and the semi-insulating GaAs photoconductive semiconductor switch is essentially a type of pho-ton-activated charge domain device.
文摘A model is presented to describe a compensation mechanism for semi-insulating 6H-SiC grown with the intentional doping of vanadium. Because we found nitrogen to be the principal shallow donor impurity in SiC by secondary ion mass spectroscopy （SIMS） measurements, semi-insulating properties in SiC are achieved by compensating the nitrogen donor with the vanadium deep acceptor level. The presence of different vanadium charge states V^3＋ and V^4＋ is detected by electron paramagnetic resonance and optical absorption measurements,which coincides with the results obtained by SIMS measurements. Both optical absorption and low temperature photoluminescence measurements reveal that the vanadium acceptor level is located at 0.62eV below the conduction band in 6H-SiC.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0403002)the National Science Fund for Distinguished Young Scholars,China(Grant No.Y3CHC11001)the National Natural Science Foundation of China(Grant No.11604368)
文摘One-port surface acoustic wave resonators(SAWRs) are fabricated on semi-insulating high-quality bulk GaN and GaN film substrates, respectively. The semi-insulating GaN substrates are grown by hydride vapor phase epitaxy(HVPE)and doped with Fe. The anisotropy of Rayleigh propagation and the electromechanical coupling coefficient in Fe-doped GaN are investigated. The difference in resonance frequency between the SAWs between [1120] GaN and [1100] GaN is about 0.25% for the Rayleigh propagation mode, which is smaller than that of non-intentionally doped GaN film(~1%)reported in the literature. The electromechanical coupling coefficient of Fe-doped GaN is about 3.03%, which is higher than that of non-intentionally doped GaN film. The one-port SAWR fabricated on an 8-μm Fe-doped GaN/sapphire substrate has a quality factor of 2050, and that fabricated on Fe-doped bulk GaN has a quality factor as high as 3650. All of our results indicate that high-quality bulk GaN is a very promising material for application in SAW devices.
基金supported by the National Natural Sci-ence Foundation of China under grant No. 50472068 and No. 50721002the National "863" High Technology Re-search and Development Program of China under grant No. 2006AA03A145 and No. 2007AA03Z405+1 种基金the Na-tional Basic Research Program of China under grant No.2009CB930503the Cultivation Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China under grant No. 707039
文摘Two-inch semi-insulating SiC bulk crystals with resistivity higher than 1 × 10^6 Qcm were achieved by vanadium doping during sublimation. Secondary-ion-mass-spectrometry （SIMS） was employed to determine the concentration of impurities in the crystals, such as B, AI, V and N. These results indicated that the concentration of nitrogen and aluminum kept on decreasing and the concentration of B and V was almost constant during the whole growth. An inner crucible was used to control the exhausting of vanadium, which made the uniformity of the high resistivity （〉1×10^6 Ωcm） in the wafer up to 80%. High-performance AlGaN/GaN high-electronmobility-transistor （HEMT） materials and devices were grown and fabricated on semi-insulating 6H-SiC sub- strates. The two-dimensional electron gas （2DEG） mobility at room-temperature was 1795 cm^2/V-s. The charge carrier concentration of the substrate determined by capacitance-voltage （C-V） test was 7.3×10^15 cm^-3. The device with a gate width of I mm exhibits a maximum output power of 5.5 W at 8 GHz, which proves the semi-insulating property of the substrates indirectly.
文摘Properties of Fe-doped semi-insulating (SI) InP with different iron concentrations are studied by using Hall effect,current-voltage ( I-V ),photoluminescence spectroscopy (PL) and photocurrent spectroscopy(PC)measurements. I-V characteristics of SI InP strongly depend on Fe doping concentration.Fe doping concentration also influences optical properties and defective formation in as-grown SI InP.Band-gap narrowing phenomenon and defects in Fe doped SI InP are studied using PL and PC.
文摘Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Experimental results indicate that, after an annealing at 950 degreesC for 14 h under low As pressure, the Hall mobility decreases and the resistivity increases dramatically for the samples. These changes in electrical properties are due to the generation of intrinsic acceptor defects, and the generation of the intrinsic acceptor defects originates from the outdiffusion of As interstitial at high temperature. The generation of the intrinsic defects and these changes in electrical properties can be suppressed by increasing the applied As pressure during annealing. The concentration of the main donor defect E12 (AsGaVGa) can be decreased by about one order of magnitude by an evacuated annealing at 1120 degreesC for 2-8 h followed by a fast cooling. The decrease in E12 concentration can also be suppressed by increasing the As pressure during annealing.
文摘We demonstrate high-performance In0.23 Ga0.77 As channel metal-oxide-semiconductor field-effect transistors （ MOS- FETs） with high on-current to off-current （Ion/Ioff） ratio grown on semi-insulating GaAs wafers by metal-organic chemical vapor deposition （MOCVD）. The 2μm channel-length devices exhibit a peak extrinsic transeonductance of 150 mS/mm and a drain current up to 500 mA/mm. The maximum effective mobility is 1680 cm2/Vs extracted by the split C-V method. Furthermore, the Ion/Ioff ratio is significantly improved from approximately 4.5 × 10^3 up to approximately 4.32 × 10^4 by controlling the etch thickness of In0.49Ga0.51P, The high drain current and high Ion/Ioff ratio of the In0.23Ga0.77As channel MOSFETs are achieved due to the high effective mobility and the low gate leakage current density.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61234006 and 61274079)the Key Specific Projects of Ministry of Education of China(Grant No.625010101)the Science Project of State Grid,China(Grant No.SGRI-WD-71-13-004)
文摘Based on the theoretical analysis of the 4H-SiC Schottky-barrier diodes （SBDs） with field plate termination, 4H-SiC SBD with semi-insulating polycrystalline silicon （SIPOS） FP termination has been fabricated. The relative dielectric con-stant of the SIPOS dielectric first used in 4H-SiC devices is 10.4, which is much higher than that of the SiO2 dielectric, leading to benefitting the performance of devices. The breakdown voltage of the fabricated SBD could reach 1200 V at leak-age current 20 μA, about 70% of the theoretical breakdown voltage. Meanwhile, both of the simulation and experimental results show that the length of the SIPOS FP termination is an important factor for structure design.
文摘The microprecipitates in the as-grown undoped and In-doped semi-insulating GaAs single crystals have been ex- amined by JEM 200 CX transmission electron microscope.The microprecipitates consist of GaAs polycrystalline grains of 5～100nm in size have been evidenced in dislocated crystals.Energy dispersive X-ray analysis shows that the mieropreeipitates are predominately arsenic-rich GaAs.The As/Ga atomic ratio of the microprecipitates in In-doped crystal is higher than that of undoped crystal.It is suggested that the formation of the microprecipitates may be induced by the local fluctuation of compositional undercooling during crystal growth.
基金supported by the Air Force Office of Scientific Research (Grant No. FA9550-10-1-0136)NASA (Grant No. 242026-1BBX11AQ36A)+1 种基金supported by a University of Arkansas Honors College Undergraduate Research grantthe Microelectronics–Photonics program at the University of Arkansas for the COMSOL license
文摘Metal-semiconductor-metal photodetectors on semi-insulating Ga As with interdigital electrodes showed significant enhancement in the spectral response in the near-infrared region as the electrode spacing is reduced. The photocurrent for the device with 5 μm interdigital spacing is five orders of magnitude higher than the dark current, and the room temperature detectivity is on the order of 2.4 × 1012cm Hz1∕2W-1at 5 V bias. Furthermore,the spectral response of this device possesses strong dependence on the polarization of incident light showing potential plasmonic effects with only microscale dimensions. These experimental data were analyzed using optical simulation to confirm the response of the devices.
基金supported by the National Natural Science Foundation of China(No.60606022)the Advanced Fund(No.9140A08050508)the Applied Materials Innovation Fund (Nos.XA-AM-200607,XA-AM-200704)
文摘The intrinsic defects in epitaxial semi-insulating 4H-SiC prepared by low pressure chemical vapor deposition （LPCVD） are studied by electron spin resonance （ESR） with different illumination times. The results show that the intrinsic defects in as-grown 4H-SiC consist of carbon vacancy （Vc） and complex-compounds-related Vc. There are two other apexes presented in the ESR spectra after illumination by Xe light, which are likely to be Vsi and VcCsi. Illumination time changes the relative density of intrinsic defects in 4H-SiC; the relative density of intrinsic defects reaches a maximum when the illumination time is 2.5 min, and the ratio of Vc to complex compounds is minimized simultaneously. It can be deduced that some Vsi may be transformed to the complex-compounds-related Vc because of the illumination.
文摘A comprehensive analysis of multi-quantum-well electroabsorption modulators buried with semi-insulating (SI)-InP is presented. We quantitatively demonstrate that suppression of Zn diffusion into the burying and optical core layers plays a key role in high-speed and high-extinction operation.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61575161 and 61427814the National Basic Research Program of China under Grant No 2014CB339800+1 种基金the Foundation of Shaanxi Key Science and Technology Innovation Team under Grant No 2014KTC-13the Special Financial Grant from the China Postdoctoral Science Foundation under Grant No 2013T60883
文摘OaAs has been widely used to fabricate a variety of optoelectronic devices by virtue of its superior performance, and it is very important to accurately measure its electrical and optical properties. In this study, a semi- insulation （SI） GaAs wafer is investigated by the terahertz （THz） non-destructive testing technology. Using an air biased coherent generation and detection THz time domain spectroscopy system, the THz time domain waveform and spectrum of SI-GaAs are obtained by the time domain spectroscopy module, and its optical- electrical characteristics including complex refractive index, permittivity and dielectric loss angle are calculated. Its carrier lifetime is measured by the optical-pump THz-probe module, and the THz pulse induced intervalley scattering in photo-excited SI-GaAs is discussed.
文摘The free electron concentration of as-grown liquid encapsulated Czochralski (LE C) InP measured by Hall effect is much higher than the concentration of net dono r impurity determined by glow discharge mass spectroscopy.Evidence of the existe nce of a native donor hydrogen-indium vacancy complex in LEC undoped and Fe-do ped InP materials can be obseved with infrared absorption spectra.The concentra tion increase of the donor complex correlates with the increase of ionized deep acceptor iron impurity Fe concentration in Fe-doped semi-insulating (S I) InP.These results indicate that the hydrogen-indium vacancy complex is an im portant donor defect in as-grown LEC InP,and that it has significant influence on the compensation in Fe-doped SI InP
文摘Gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS's) with a 1.55mm gap spacing trigged by 1553nm femtosecond fiber laser pulse is presented.The switches are biased with 3.33～10.3kV/cm and irradiated by femtosecond fiber laser operated at a wavelength of 1553nm with pulse width of 200fs and pulse energy of 0.2nJ.The experiments show that,even if the semi-insulating GaAs photoconductive switch operates under the electrical field of 10.3kV/cm,it will be still linear response,and a clear corresponding output electric pulse with the peak voltage of 0.8mV is captured.From the weak photoconductivity on laser intensity,photoabsorption mediated by EL2 deep level defects is suggested,as the primary process for the photoconductivity.
文摘The diffusion behavior of vanadium （V） implanted in SiC is investigated by secondary ion mass spec- trometry. Significant redistribution, especially out-diffusion of vanadium towards the sample surface, is not ob- served after 1650℃ annealing. Higher carrier concentration is obtained due to a lack of compensation of vanadium in the surface region. The electrical characteristics of Ni contacts to V-implanted n-type 4H-SiC are investigated using a linear transmission line method. A specific contact resistance as low as 4.4 × 10^-3Ω · cmA^2 is achieved after annealing at 1050℃ for 10min in gas ambient consisting of 90% N2 and 10% H2 X-ray diffraction analysis shows the formation of Ni2 Si and graphite phase at the interface after annealing. This provides the evidence that the car- bon vacancies,resulting from the out-diffusion of carbon atoms from SiC, contribute to the formation of ohmic contact through the reduction of effective Schottky barrier height for the transport of electrons.
基金Project supported by the National Natural Science Foundation of China （Grant No 60376001）, the National Basic Research Program of China （Grant No 2002CB311904） and the National Defense Basic Research Program of China （Grant No 51327020202）. Acknowledgments The authors would like to thank Li Cheng-Ji and Ye Xiao-Ling of Institute of Semiconductors, Chinese Academy of Sciences for measuring the temperaturedependent resistivity and absorption, respectively, and they also thank Ma Nong-Nong at the Centre of Electronic Materials Characterization of Tianjin Electronic Materials Research Institute for performing SIMS measurements.
文摘A semi-insulating layer is obtained in n-type 4H-SiC by vanadium-ion implantation. A little higher resistivity is obtained by increasing the annealing temperature from 1450 to 1650 ℃. The resistivity at room temperature is as high as 7.6 ×10^6 Ω. cm. Significant redistribution of vanadium is not observed even after 1650 ℃ annealing. Temperaturedependent resistivity and optical absorption of V-implanted samples are measured. The activation energy of vanadium acceptor level is observed to be at about Ec - 1.1 eV.
文摘This paper describes an experimental and theoretical study on an extraction phenomenon of liquids occurring at an air gap between the liquid surface and the electrode by applying a direct current (DC) or low-frequency alternating current (AC) voltage. Three liquids with a different physical property;2,3-dihydrodecafluoropenten, palm fatty acid ester oil and crude rapeseed oil are used as working liquids. The electrode configuration is the sphere or plane (high voltage electrode) to grounded plane electrode. The grounded plane electrode is fixed to the bottom of the test vessel with working liquid and the high voltage electrode is installed in an air above the liquid surface against the grounded plane electrode. The liquid surface swells towards the high voltage electrode by the increase of voltage and the liquid is extracted in a short time, thereafter the air gap between the liquid surface and the high voltage electrode is bridged at a thick liquid column. Such the liquid behavior displays unique features with voltage polarity effect for each working liquid. The relationship between the applied voltage, current variation, height of swollen liquid, force pulling liquid and dynamic feature of liquid is examined experimentally. The liquid behavior is considered theoretically based on experimental observations.
基金Project supported by the National Natural Science Foundation of China(No.61464002)the Science and Technology Fund of Guizhou Province(No.Qian Ke He J Zi[2014]2066)the Dr.Fund of Guizhou University(No.Gui Da Ren Ji He Zi(2013)20Hao)
文摘A new semi-insulation structure in which one isolated island is connected to the substrate was pro- posed. Based on this semi-insulation structure, an advanced BCD technology which can integrate a vertical de- vice without extra internal interconnection structure was presented. The manufacturing of the new semi-insulation structure employed multi-epitaxy and selectively multi-doping. Isolated islands are insulated with the substrate by reverse-biased PN junctions. Adjacent isolated islands are insulated by isolation wall or deep dielectric trenches. The proposed semi-insulation structure and devices fixed in it were simulated through two-dimensional numerical computer simulators. Based on the new BCD technology, a smart power integrated circuit was designed and fabri- cated. The simulated and tested results of Vertical DMOS, MOSFETs, BJTs, resistors and diodes indicated that the proposed semi-insulation structure is reasonable and the advanced BCD technology is validated.
