基于密度泛函理论的第一性原理平面波超软赝势方法,建立了本征SnO_2、SnO_2∶In、SnO_2∶Ga和SnO_2∶(In,Ga)超晶胞模型并进行了几何结构优化,对其能带结构、态密度、电荷密度及光学性质进行了模拟计算.结果显示,与SnO_2∶In和SnO_2∶G...基于密度泛函理论的第一性原理平面波超软赝势方法,建立了本征SnO_2、SnO_2∶In、SnO_2∶Ga和SnO_2∶(In,Ga)超晶胞模型并进行了几何结构优化,对其能带结构、态密度、电荷密度及光学性质进行了模拟计算.结果显示,与SnO_2∶In和SnO_2∶Ga相比,SnO_2∶(In,Ga)的晶格常数更接近于本征SnO_2,可有效降低SnO_2材料掺杂体系的晶格畸变.SnO_2中In、Ga的掺入能够增大材料的带隙值,且能带结构向高能方向移动,材料呈现典型的p型半导体特性.SnO_2∶(In,Ga)中,In与Ga掺杂原子和O原子的电子云呈现出共价键特性.光学性能表明,SnO_2∶(In,Ga)晶体中,光子能量在0~2.45 e V和大于6.27 e V的范围内表现出良好的介电性能,在微型微电子传感器机械系统器件和高密度信息存储等方面具有良好的应用前景.SnO_2∶(In,Ga)在可见光范围内具有10~5cm^(-1)数量级的吸收系数,能够强烈地吸收光能,在光电器件的吸收材料中具有潜在的应用前景.展开更多
采用单辊旋淬法制备了Cu45Zr42.55Y3.45Al9非晶合金,差示扫描量热分析手段(DSC)研究了该非晶合金晶化动力学性能.采用Ozawa,Kissinger及Augis-Bennett方法计算了Cu45Zr42.55Y3.45Al9非晶合金晶化激活能,得到第一晶化峰值激活能1pE分别是...采用单辊旋淬法制备了Cu45Zr42.55Y3.45Al9非晶合金,差示扫描量热分析手段(DSC)研究了该非晶合金晶化动力学性能.采用Ozawa,Kissinger及Augis-Bennett方法计算了Cu45Zr42.55Y3.45Al9非晶合金晶化激活能,得到第一晶化峰值激活能1pE分别是385.8,393.5,396.0 k J·mol-1.发现Cu45Zr42.55Y3.45Al9合金具有很好的热稳定性.展开更多
利用脉冲激光沉积(PLD)设备在蓝宝石衬底上制备了高质量Zn_(1-x)Mg_xO单晶薄膜,并对其结构和光学特性进行了深入细致的研究。通过能量衍射谱(EDS)确认Zn_(1-x)Mg_xO薄膜的Mg组分为45%。在Zn0.55Mg0.45O薄膜的X射线衍射谱(XRD)中观测到...利用脉冲激光沉积(PLD)设备在蓝宝石衬底上制备了高质量Zn_(1-x)Mg_xO单晶薄膜,并对其结构和光学特性进行了深入细致的研究。通过能量衍射谱(EDS)确认Zn_(1-x)Mg_xO薄膜的Mg组分为45%。在Zn0.55Mg0.45O薄膜的X射线衍射谱(XRD)中观测到了明显的位于36.67°的衍射峰,对应的是(111)晶向的立方相ZnMgO。从透射光谱中可以看出,Zn0.55Mg0.45O具有陡峭的吸收边,没有发生相分离,在透射电镜图谱中也得到了证实。该ZnMgO薄膜还表现出了优异的光学特性,在Zn0.55Mg0.45O材料体系中实现了峰位位于310 nm的紫外光泵浦受激发射,其激光发射的阈值仅为22 k W/cm2。展开更多
We investigate the performances of the near-ultraviolet（about 350 nm-360 nm） light-emitting diodes（LEDs） each with specifically designed irregular sawtooth electron blocking layer（EBL） by using the APSYS simulat...We investigate the performances of the near-ultraviolet（about 350 nm-360 nm） light-emitting diodes（LEDs） each with specifically designed irregular sawtooth electron blocking layer（EBL） by using the APSYS simulation program.The internal quantum efficiencies（IQEs）,light output powers,carrier concentrations in the quantum wells,energy-band diagrams,and electrostatic fields are analyzed carefully.The results indicate that the LEDs with composition-graded pAlxGa1-xN irregular sawtooth EBLs have better performances than their counterparts with stationary component p-AlGaN EBLs.The improvements can be attributed to the improved polarization field in EBL and active region as well as the alleviation of band bending in the EBL/p-AlGaN interface,which results in less electron leakage and better hole injection efficiency,thus reducing efficiency droop and enhancing the radiative recombination rate.展开更多
In this paper we report on the effect of an lnxGal xN continuously graded buffer layer on an InGaN epilayer grown on a GaN template. In our experiment, three types of buffer layers including constant composition, cont...In this paper we report on the effect of an lnxGal xN continuously graded buffer layer on an InGaN epilayer grown on a GaN template. In our experiment, three types of buffer layers including constant composition, continuously graded composition, and the combination of constant and continuously graded composition are used. Surface morphologies, crystalline quality, indium incorporations, and relaxation degrees of InGaN epilayers with different buffer layers are investigated. It is found that the InxGa1-xN continuously graded buffer layer is effective to improve the surface morphology, crystalline quality, and the indium incorporation of the InGaN epilayer. These superior characteristics of the continuously graded buffer layer can be attributed to the sufficient strain release and the reduction of dislocations.展开更多
We use a simple and controllable method to fabricate GaN-based light-emitting diodes （LEDs） with 22° undercut sidewalls by the successful implementation of the inductively coupled plasma reactive ion etching （...We use a simple and controllable method to fabricate GaN-based light-emitting diodes （LEDs） with 22° undercut sidewalls by the successful implementation of the inductively coupled plasma reactive ion etching （ICP-RIE）. Our exper- iment results show that the output powers of the LEDs with 22° undercut sidewalls are 34.8 rnW under a 20-mA current injection, 6.75% higher than 32.6 mW, the output powers of the conventional LEDs under the same current injection.展开更多
Influences of the Si doping on the structural and optical properties of the InGaN epilayers are investigated in detail by means of high-resolution X-ray diffraction （HRXRD）, photolumimescence （PL）, scanning electr...Influences of the Si doping on the structural and optical properties of the InGaN epilayers are investigated in detail by means of high-resolution X-ray diffraction （HRXRD）, photolumimescence （PL）, scanning electron microscope （SEM）, and atomic force microscopy （AFM）. It is found that the Si doping may improve the surface morphology and crystal quality of the InGaN film and meanwhile it can also enhance the emission efficiency by increasing the electron concentration in the InGaN and suppressing tile formation of V-defects, which act as nonradiative recombination centers in the InGaN, and it is proposed that the former plays a more important role in enhancing the emission efficiency in the InGaN.展开更多
ZnO nanowall networks were prepared by plasma-assisted molecular beam epitaxy without a catalyst on Si（111） substrates.The nanostructures have preferred orientation along the c axis.The nanostructures are about 10 t...ZnO nanowall networks were prepared by plasma-assisted molecular beam epitaxy without a catalyst on Si（111） substrates.The nanostructures have preferred orientation along the c axis.The nanostructures are about 10 to 20 nm thick and about 50 nm tall.The planar geometry photoconductive type metal-semiconductor-metal photodetector based on the ZnO nanowall networks exhibits a high and wide response spectrum,and no decrease from 250 to 360 nm.With the applied bias below 5 V,the dark current was below 6μA,and the peak responsivity of 15 A/W was achieved at 360 nm.The UV（360 nm） to visible（450 nm） rejection ratio of around two orders could be extracted from the spectra response.展开更多
文摘基于密度泛函理论的第一性原理平面波超软赝势方法,建立了本征SnO_2、SnO_2∶In、SnO_2∶Ga和SnO_2∶(In,Ga)超晶胞模型并进行了几何结构优化,对其能带结构、态密度、电荷密度及光学性质进行了模拟计算.结果显示,与SnO_2∶In和SnO_2∶Ga相比,SnO_2∶(In,Ga)的晶格常数更接近于本征SnO_2,可有效降低SnO_2材料掺杂体系的晶格畸变.SnO_2中In、Ga的掺入能够增大材料的带隙值,且能带结构向高能方向移动,材料呈现典型的p型半导体特性.SnO_2∶(In,Ga)中,In与Ga掺杂原子和O原子的电子云呈现出共价键特性.光学性能表明,SnO_2∶(In,Ga)晶体中,光子能量在0~2.45 e V和大于6.27 e V的范围内表现出良好的介电性能,在微型微电子传感器机械系统器件和高密度信息存储等方面具有良好的应用前景.SnO_2∶(In,Ga)在可见光范围内具有10~5cm^(-1)数量级的吸收系数,能够强烈地吸收光能,在光电器件的吸收材料中具有潜在的应用前景.
文摘采用单辊旋淬法制备了Cu45Zr42.55Y3.45Al9非晶合金,差示扫描量热分析手段(DSC)研究了该非晶合金晶化动力学性能.采用Ozawa,Kissinger及Augis-Bennett方法计算了Cu45Zr42.55Y3.45Al9非晶合金晶化激活能,得到第一晶化峰值激活能1pE分别是385.8,393.5,396.0 k J·mol-1.发现Cu45Zr42.55Y3.45Al9合金具有很好的热稳定性.
基金Supported by National Natural Science Foundation of China(61574063)Science and Technology Program of Guangdong Province(2016A040403106)Science and Technology Project of Guangzhou City(2016201604030047)~~
文摘利用脉冲激光沉积(PLD)设备在蓝宝石衬底上制备了高质量Zn_(1-x)Mg_xO单晶薄膜,并对其结构和光学特性进行了深入细致的研究。通过能量衍射谱(EDS)确认Zn_(1-x)Mg_xO薄膜的Mg组分为45%。在Zn0.55Mg0.45O薄膜的X射线衍射谱(XRD)中观测到了明显的位于36.67°的衍射峰,对应的是(111)晶向的立方相ZnMgO。从透射光谱中可以看出,Zn0.55Mg0.45O具有陡峭的吸收边,没有发生相分离,在透射电镜图谱中也得到了证实。该ZnMgO薄膜还表现出了优异的光学特性,在Zn0.55Mg0.45O材料体系中实现了峰位位于310 nm的紫外光泵浦受激发射,其激光发射的阈值仅为22 k W/cm2。
基金supported by the National Natural Science Foundation of China(Grant Nos.11474105 and 51172079)the Science and Technology Program of Guangdong Province,China(Grant Nos.2015B090903078 and 2015B010105011)+2 种基金the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT13064)the Science and Technology Project of Guangzhou City,China(Grant No.201607010246)the Science and Technology Planning Project of Guangdong Province,China(Grant No.2015A010105025)
文摘We investigate the performances of the near-ultraviolet（about 350 nm-360 nm） light-emitting diodes（LEDs） each with specifically designed irregular sawtooth electron blocking layer（EBL） by using the APSYS simulation program.The internal quantum efficiencies（IQEs）,light output powers,carrier concentrations in the quantum wells,energy-band diagrams,and electrostatic fields are analyzed carefully.The results indicate that the LEDs with composition-graded pAlxGa1-xN irregular sawtooth EBLs have better performances than their counterparts with stationary component p-AlGaN EBLs.The improvements can be attributed to the improved polarization field in EBL and active region as well as the alleviation of band bending in the EBL/p-AlGaN interface,which results in less electron leakage and better hole injection efficiency,thus reducing efficiency droop and enhancing the radiative recombination rate.
基金Project supported by the National High Technology Research and Development Program of China (Grant Nos.2011AA03A112,2011AA03A106,and 2013AA03A101)the National Natural Science Foundation of China (Grant Nos.11204360,61210014,and 61078046)+2 种基金the Science & Technology Innovation Program of the Department of Education of Guangdong Province,China (Grant No.2012CXZD0017)the Industry–Academia-Research Union Special Fund of Guangdong Province,China (Grant No.2012B091000169)the Science & Technology Innovation Platform of Industry–Academia-Research Union of Guangdong Province–Ministry Cooperation Special Fund,China (Grant No.2012B090600038)
文摘In this paper we report on the effect of an lnxGal xN continuously graded buffer layer on an InGaN epilayer grown on a GaN template. In our experiment, three types of buffer layers including constant composition, continuously graded composition, and the combination of constant and continuously graded composition are used. Surface morphologies, crystalline quality, indium incorporations, and relaxation degrees of InGaN epilayers with different buffer layers are investigated. It is found that the InxGa1-xN continuously graded buffer layer is effective to improve the surface morphology, crystalline quality, and the indium incorporation of the InGaN epilayer. These superior characteristics of the continuously graded buffer layer can be attributed to the sufficient strain release and the reduction of dislocations.
基金Project supported by the National High Technology Research and Development Program of China (Grant Nos.2011AA03A112,2011AA03A106,and 2013AA03A101)the National Natural Science Foundation of China (Grant Nos.11204360,61210014,and 61078046)+2 种基金the Science and Technology Innovation Program of Department of Education of Guangdong Province,China (Grant No.2012CXZD0017)the Industry–Academia Research Union Special Fund of Guangdong Province,China (Grant No.2012B091000169)the Science and Technology Innovation Platform of Industry–Academia Research Union of Guangdong Province–Ministry Cooperation Special Fund,China (Grant No.2012B090600038)
文摘We use a simple and controllable method to fabricate GaN-based light-emitting diodes （LEDs） with 22° undercut sidewalls by the successful implementation of the inductively coupled plasma reactive ion etching （ICP-RIE）. Our exper- iment results show that the output powers of the LEDs with 22° undercut sidewalls are 34.8 rnW under a 20-mA current injection, 6.75% higher than 32.6 mW, the output powers of the conventional LEDs under the same current injection.
基金Project supported by the National High Technology Research and Development Program of China (Grant Nos.2011AA03A112,2011AA03A106,and 2013AA03A101)the National Natural Science Foundation of China (Grant Nos.11204360,61210014,and 61078046)+2 种基金the Science & Technology Innovation Program of Department of Education of Guangdong Province,China (Grant No.2012CXZD0017)the Industry–Academia Research Union Special Fund of Guangdong Province,China (Grant No.2012B091000169)the Science & Technology Innovation Platform of Industry–Academia Research Union of Guangdong Province–Ministry Cooperation Special Fund,China (Grant No.2012B090600038)
文摘Influences of the Si doping on the structural and optical properties of the InGaN epilayers are investigated in detail by means of high-resolution X-ray diffraction （HRXRD）, photolumimescence （PL）, scanning electron microscope （SEM）, and atomic force microscopy （AFM）. It is found that the Si doping may improve the surface morphology and crystal quality of the InGaN film and meanwhile it can also enhance the emission efficiency by increasing the electron concentration in the InGaN and suppressing tile formation of V-defects, which act as nonradiative recombination centers in the InGaN, and it is proposed that the former plays a more important role in enhancing the emission efficiency in the InGaN.
基金Project supported by the Grow Seedlings Project of Guangdong Province,China(No.LYM 10063)
文摘ZnO nanowall networks were prepared by plasma-assisted molecular beam epitaxy without a catalyst on Si（111） substrates.The nanostructures have preferred orientation along the c axis.The nanostructures are about 10 to 20 nm thick and about 50 nm tall.The planar geometry photoconductive type metal-semiconductor-metal photodetector based on the ZnO nanowall networks exhibits a high and wide response spectrum,and no decrease from 250 to 360 nm.With the applied bias below 5 V,the dark current was below 6μA,and the peak responsivity of 15 A/W was achieved at 360 nm.The UV（360 nm） to visible（450 nm） rejection ratio of around two orders could be extracted from the spectra response.
