The surface morphology of GaN grown by MOCVD on GaN/Si template was studied.Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied.The formation of rough morphology is...The surface morphology of GaN grown by MOCVD on GaN/Si template was studied.Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied.The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature.The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template.The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects.The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature.展开更多
Pulsed power technology has an important trend in the world,which has high power,long pulse,high operating frequency and miniaturization.Thus all-solid-state pulsed power technologies based on semiconductor devices ha...Pulsed power technology has an important trend in the world,which has high power,long pulse,high operating frequency and miniaturization.Thus all-solid-state pulsed power technologies based on semiconductor devices have drawn more attention and widely used.This article introduces several kinds of semiconductor switches,such as SCR,IGBT,and SOS.The charging system based on SCR,the Marx generator,and pulsed transformer topology using IGBTs,and the system using SOS are described in detail.Some experimental results are also given.The use of semiconductor switches technology in solid state Marx generate can solve the disappointments such as short life time, low operating frequency,low reliability of conventional pulsed power equipments and has extensive perspective.展开更多
This paper presents a theoretical study of the pulse-width effects on the damage process of a typical bipolar transistor caused by high power microwaves（HPMs） through the injection approach.The dependences of the mi...This paper presents a theoretical study of the pulse-width effects on the damage process of a typical bipolar transistor caused by high power microwaves（HPMs） through the injection approach.The dependences of the microwave damage power,P,and the absorbed energy,E,required to cause the device failure on the pulse width τ are obtained in the nanosecond region by utilizing the curve fitting method.A comparison of the microwave pulse damage data and the existing dc pulse damage data for the same transistor is carried out.By means of a two-dimensional simulator,ISE-TCAD,the internal damage processes of the device caused by microwave voltage signals and dc pulse voltage signals are analyzed comparatively.The simulation results suggest that the temperature-rising positions of the device induced by the microwaves in the negative and positive half periods are different,while only one hot spot exists under the injection of dc pulses.The results demonstrate that the microwave damage power threshold and the absorbed energy must exceed the dc pulse power threshold and the absorbed energy,respectively.The dc pulse damage data may be useful as a lower bound for microwave pulse damage data.展开更多
A novel silicon double-RESURF LDMOS structure with an improved breakdown characteristic by substrate bias technology（SB） is reported.The P-type epitaxial layer is embedded between an N-type drift region and an N-typ...A novel silicon double-RESURF LDMOS structure with an improved breakdown characteristic by substrate bias technology（SB） is reported.The P-type epitaxial layer is embedded between an N-type drift region and an N-type substrate to block the conduction path in the off-state and change the distributions of the bulk electric field.The substrate bias strengthens the charge share effect of the drift region near the source,and the vertical electric field peak under the drain is decreased,which is especially helpful in improving the vertical breakdown voltage in a lateral power device with a thin drift region.The numerical results by MEDICI indicate that the breakdown voltage of the proposed device is increased by 97%compared with a conventional LDMOS,while maintaining a low on-resistance.展开更多
Phosphor plays an important role in LED packages by converting the wavelength of light and achieving specific color. The property and degradation of phosphor are strongly affected by the temperature. Some structural f...Phosphor plays an important role in LED packages by converting the wavelength of light and achieving specific color. The property and degradation of phosphor are strongly affected by the temperature. Some structural factors have been investigated in this paper and their effects are evaluated. Remote phosphor is an effective approach to improve the performance and reliability of LED modules and products. It is a trade-off that the final product design depends on both the thermal performance and the cost.展开更多
In this study, B-doped ZnO nanoparticles were synthesized by template-free solvothermal method. X-ray diffraction analysis reveals that B-doped ZnO nanoparti- cles have hexagonal wurtzite structure. Field emission sca...In this study, B-doped ZnO nanoparticles were synthesized by template-free solvothermal method. X-ray diffraction analysis reveals that B-doped ZnO nanoparti- cles have hexagonal wurtzite structure. Field emission scanning electron microscopy observations show that the nanoparticles have a diameter of 50 nm. The room tem- perature ferromagnetism increases monotonically with increasing B concentration to the ZnO nanoparticles and reaches the maximum value of saturation magnetization 0.0178 A.ma.kg-1 for 5 % B-doped ZnO nanoparticles. Moreover, photoluminescence spectra reveal that B doping causes to produce Zn vacancies （Vzn）. Magnetic moment of oxygen atoms nearest to the B-Vzn vacancy pairs can be considered as a source of ferromagnetism for B-doped ZnO nanoparticles.展开更多
基金Project supported by Special Funds for Major State Basic Research Project(G2000683 and 2002CB311903)Nationel Natural Foundation of China(60136020)Key Imnovation Program of Chinese Academy of Science and National High Technology R&D Pogram of China(2002AA305304)
文摘The surface morphology of GaN grown by MOCVD on GaN/Si template was studied.Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied.The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature.The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template.The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects.The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature.
文摘Pulsed power technology has an important trend in the world,which has high power,long pulse,high operating frequency and miniaturization.Thus all-solid-state pulsed power technologies based on semiconductor devices have drawn more attention and widely used.This article introduces several kinds of semiconductor switches,such as SCR,IGBT,and SOS.The charging system based on SCR,the Marx generator,and pulsed transformer topology using IGBTs,and the system using SOS are described in detail.Some experimental results are also given.The use of semiconductor switches technology in solid state Marx generate can solve the disappointments such as short life time, low operating frequency,low reliability of conventional pulsed power equipments and has extensive perspective.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60776034)
文摘This paper presents a theoretical study of the pulse-width effects on the damage process of a typical bipolar transistor caused by high power microwaves（HPMs） through the injection approach.The dependences of the microwave damage power,P,and the absorbed energy,E,required to cause the device failure on the pulse width τ are obtained in the nanosecond region by utilizing the curve fitting method.A comparison of the microwave pulse damage data and the existing dc pulse damage data for the same transistor is carried out.By means of a two-dimensional simulator,ISE-TCAD,the internal damage processes of the device caused by microwave voltage signals and dc pulse voltage signals are analyzed comparatively.The simulation results suggest that the temperature-rising positions of the device induced by the microwaves in the negative and positive half periods are different,while only one hot spot exists under the injection of dc pulses.The results demonstrate that the microwave damage power threshold and the absorbed energy must exceed the dc pulse power threshold and the absorbed energy,respectively.The dc pulse damage data may be useful as a lower bound for microwave pulse damage data.
基金Project supported by the Guangxi Natural Science Foundation of China(No.2010GXNSFB013054)the Guangxi Key Science and Technology Program of China(No.11107001-20)
文摘A novel silicon double-RESURF LDMOS structure with an improved breakdown characteristic by substrate bias technology（SB） is reported.The P-type epitaxial layer is embedded between an N-type drift region and an N-type substrate to block the conduction path in the off-state and change the distributions of the bulk electric field.The substrate bias strengthens the charge share effect of the drift region near the source,and the vertical electric field peak under the drain is decreased,which is especially helpful in improving the vertical breakdown voltage in a lateral power device with a thin drift region.The numerical results by MEDICI indicate that the breakdown voltage of the proposed device is increased by 97%compared with a conventional LDMOS,while maintaining a low on-resistance.
基金the companies and organizations of China Solid-state Lighting Association(CSA) that support research activities at the State Key Laboratory of Solid-State Lighting
文摘Phosphor plays an important role in LED packages by converting the wavelength of light and achieving specific color. The property and degradation of phosphor are strongly affected by the temperature. Some structural factors have been investigated in this paper and their effects are evaluated. Remote phosphor is an effective approach to improve the performance and reliability of LED modules and products. It is a trade-off that the final product design depends on both the thermal performance and the cost.
基金financially supported by the National Natural Science Foundation of China (Nos. 50831002, 51271020, 51071022, and 11174031)the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT1106)+2 种基金Beijing Nova Program (No. 2011031)the Beijing Municipal Natural Science Foundation (No. 2102032)the Fundamental Research Funds for the Central Universities
文摘In this study, B-doped ZnO nanoparticles were synthesized by template-free solvothermal method. X-ray diffraction analysis reveals that B-doped ZnO nanoparti- cles have hexagonal wurtzite structure. Field emission scanning electron microscopy observations show that the nanoparticles have a diameter of 50 nm. The room tem- perature ferromagnetism increases monotonically with increasing B concentration to the ZnO nanoparticles and reaches the maximum value of saturation magnetization 0.0178 A.ma.kg-1 for 5 % B-doped ZnO nanoparticles. Moreover, photoluminescence spectra reveal that B doping causes to produce Zn vacancies （Vzn）. Magnetic moment of oxygen atoms nearest to the B-Vzn vacancy pairs can be considered as a source of ferromagnetism for B-doped ZnO nanoparticles.
