The InGaN films and GaN/InGaN/GaN tunnel junctions(TJs)were grown on GaN templates with plasma-assisted molecular beam epitaxy.As the In content increases,the quality of InGaN films grown on GaN templates decreases an...The InGaN films and GaN/InGaN/GaN tunnel junctions(TJs)were grown on GaN templates with plasma-assisted molecular beam epitaxy.As the In content increases,the quality of InGaN films grown on GaN templates decreases and the surface roughness of the samples increases.V-pits and trench defects were not found in the AFM images.p++-GaN/InGaN/n++-GaN TJs were investigated for various In content,InGaN thicknesses and doping concentration in the InGaN insert layer.The InGaN insert layer can promote good interband tunneling in GaN/InGaN/GaN TJ and significantly reduce operating voltage when doping is sufficiently high.The current density increases with increasing In content for the 3 nm InGaN insert layer,which is achieved by reducing the depletion zone width and the height of the potential barrier.At a forward current density of 500 A/cm^(2),the measured voltage was 4.31 V and the differential resistance was measured to be 3.75×10^(−3)Ω·cm^(2)for the device with a 3 nm p++-In_(0.35)Ga_(0.65)N insert layer.When the thickness of the In_(0.35)Ga_(0.65)N layer is closer to the“balanced”thickness,the TJ current density is higher.If the thickness is too high or too low,the width of the depletion zone will increase and the current density will decrease.The undoped InGaN layer has a better performance than n-type doping in the TJ.Polarization-engineered tunnel junctions can enhance the functionality and performance of electronic and optoelectronic devices.展开更多
设计了中心波长为520 nm的AlGaInN/InGaN应变补偿分布布拉格反射镜(DBR)结构,通过调节组分参数实现应变补偿,使DBR整体应变为0,采用传输矩阵法,计算了Al_(0.7)Ga_(0.3-x)In x N/InGaN DBR、Al_(0.8)Ga_(0.2-x)In x N/InGaN DBR、Al_(0.9...设计了中心波长为520 nm的AlGaInN/InGaN应变补偿分布布拉格反射镜(DBR)结构,通过调节组分参数实现应变补偿,使DBR整体应变为0,采用传输矩阵法,计算了Al_(0.7)Ga_(0.3-x)In x N/InGaN DBR、Al_(0.8)Ga_(0.2-x)In x N/InGaN DBR、Al_(0.9)Ga_(0.1-x)In x N/InGaN DBR的反射光谱。通过对DBR结构参数进行对比,优化了其结构和反射性能。首先对比高低折射率层生长顺序,发现对于Al_(0.8)Ga_(0.14)In_(0.06)N/In_(0.123)Ga_(0.877)N DBR,先生长高折射率层时,反射率高达99.61%,而先生长低折射率层时,反射率仅为97.73%;然后对比奇数层DBR和偶数层DBR,发现两者的反射谱几乎重合,没有显著区别;通过研究DBR对数对反射率的影响,发现对数在20~30对时,反射率随着对数的增加明显上升,30~40对时反射率增长缓慢;最后研究了材料组分对反射谱的影响,发现Al组分高的DBR折射率差大,反射性能更优,而相同Al组分的AlGaInN中In含量越低反射率越高。考虑到DBR制备过程中可能出现的厚度和组分偏差,模拟了厚度和组分出现偏差时反射谱的变化,发现高低折射率层厚度每增加或减少1 nm,反射谱红移或蓝移4~5 nm;而组分的偏差使高反射带带宽和中心波长处反射率发生明显变化。本文的研究为AlGaInN/InGaN DBR的设计和制备提供了一定的理论参考。展开更多
为探究不同铟(In)组分In_(x)Ga_(1-x)N势垒对绿光激光二极管光电性能的影响,本文采用SiLENSe(simulator of light emitters based on nitride semiconductors)仿真软件对一系列具有不同In组分In_(x)Ga_(1-x)N势垒的激光二极管进行研究,...为探究不同铟(In)组分In_(x)Ga_(1-x)N势垒对绿光激光二极管光电性能的影响,本文采用SiLENSe(simulator of light emitters based on nitride semiconductors)仿真软件对一系列具有不同In组分In_(x)Ga_(1-x)N势垒的激光二极管进行研究,结果发现In_(x)Ga_(1-x)N势垒中In组分最佳值为3%,此时结构的斜率效率最高,内部光学损耗最低,光学限制因子最大,性能最优。在具有In_(0.03)Ga_(0.97_N势垒的多量子阱结构基础上,设计了一种组分阶梯(composition step-graded,CSG)InGaN势垒多量子阱结构,提高了激光二极管的斜率效率和电光转换效率,增加了光场限制能力。仿真结果表明,当注入电流为120 mA时,具有CSG InGaN势垒的多量子阱结构,电光转换效率从17.7%提高至19.9%,斜率效率从1.09 mW/mA增加到1.14 mW/mA,光学限制因子从1.58%增加到1.62%。本文的研究为制备高功率GaN基绿光激光二极管提供了理论指导和数据支撑。展开更多
The nano-patterned InGaN film was used in green InGaN/GaN multiple quantum wells(MQWs)structure,to relieve the unpleasantly existing mismatch between high indium content InGaN and GaN,as well as to enhance the light o...The nano-patterned InGaN film was used in green InGaN/GaN multiple quantum wells(MQWs)structure,to relieve the unpleasantly existing mismatch between high indium content InGaN and GaN,as well as to enhance the light output.The different self-assembled nano-masks were formed on InGaN by annealing thin Ni layers of different thicknesses.Whereafter,the InGaN films were etched into nano-patterned films.Compared with the green MQWs structure grown on untreated InGaN film,which on nano-patterned InGaN had better luminous performance.Among them the MQWs performed best when 3 nm thick Ni film was used as mask,because that optimally balanced the effects of nano-patterned InGaN on the crystal quality and the light output.展开更多
Room temperature low threshold lasing of green GaNbased vertical cavity surface emitting laser(VCSEL)was demonstrated under continuous wave(CW)operation.By using self-formed InGaN quantum dots(QDs)as the active region...Room temperature low threshold lasing of green GaNbased vertical cavity surface emitting laser(VCSEL)was demonstrated under continuous wave(CW)operation.By using self-formed InGaN quantum dots(QDs)as the active region,the VCSEL emitting at 524.0 nm has a threshold current density of 51.97 A cm^(-2),the lowest ever reported.The QD epitaxial wafer featured with a high IQE of 69.94%and theδ-function-like density of states plays an important role in achieving low threshold current.Besides,a short cavity of the device(~4.0λ)is vital to enhance the spontaneous emission coupling factor to 0.094,increase the gain coefficient factor,and decrease the optical loss.To improve heat dissipation,AlN layer was used as the current confinement layer and electroplated copper plate was used to replace metal bonding.The results provide important guidance to achieving high performance GaN-based VCSELs.展开更多
Miniaturization of light-emitting diodes(LEDs) with sizes down to a few micrometers has become a hot topic in both academia and industry due to their attractive applications on self-emissive displays for high-definiti...Miniaturization of light-emitting diodes(LEDs) with sizes down to a few micrometers has become a hot topic in both academia and industry due to their attractive applications on self-emissive displays for high-definition televisions,augmented/mixed realities and head-up displays, and also on optogenetics, high-speed light communication, etc. The conventional top-down technology uses dry etching to define the LED size, leading to damage to the LED side walls.Since sizes of microLEDs approach the carrier diffusion length, the damaged side walls play an important role, reducing microLED performance significantly from that of large area LEDs. In this paper, we review our efforts on realization of microLEDs by direct bottom-up growth, based on selective area metal–organic vapor phase epitaxy. The individual LEDs based on either GaN nanowires or InGaN platelets are smaller than 1 μm in our approach. Such nano-LEDs can be used as building blocks in arrays to assemble microLEDs with different sizes, avoiding the side wall damage by dry etching encountered for the top-down approach. The technology of InGaN platelets is especially interesting since InGaN quantum wells emitting red, green and blue light can be grown on such platelets with a low-level of strain by changing the indium content in the InGaN platelets. This technology is therefore very attractive for highly efficient microLEDs of three primary colors for displays.展开更多
利用 LP- MOCVD技术在 Ga As( 0 0 1 )衬底上生长了高质量的立方相 In Ga N外延层 .研究了生长速率对 In Ga N质量的影响 ,提出一个简单模型解释了在改变 TEGa流量条件下出现的In组分的变化规律 ,实验结果与模型的一次项拟合结果较为吻...利用 LP- MOCVD技术在 Ga As( 0 0 1 )衬底上生长了高质量的立方相 In Ga N外延层 .研究了生长速率对 In Ga N质量的影响 ,提出一个简单模型解释了在改变 TEGa流量条件下出现的In组分的变化规律 ,实验结果与模型的一次项拟合结果较为吻合 ,由此推断 ,在现在的生长条件下 ,表面单个 Ga原子作为临界晶核吸附 Ga或 In原子实现生长的模型与实际情况较为接近 .对于晶体质量的变化也给予了说明 .得到的高质量立方相 In Ga N室温下有很强的发光峰 ,光致发光峰半高宽为 1 2 8me V左右 .展开更多
基金National Natural Science Foundation of China(No.62204127)the Natural Science Foundation of Jiangsu Province(No.BK20215093)State Key Laboratory of Luminescence and Applications(No.SKLA‒2021‒04)。
基金supported by the National Key Research and Development Program of China (2017YFE0131500, 2022YFB2802801)the National Natural Science Foundation of China (61834008, U21A20493)+1 种基金the Key Research and Development Program of Jiangsu Province (BE2020004, BE2021008-1)the Suzhou Key Laboratory of New-type Laser Display Technology (SZS2022007)
文摘The InGaN films and GaN/InGaN/GaN tunnel junctions(TJs)were grown on GaN templates with plasma-assisted molecular beam epitaxy.As the In content increases,the quality of InGaN films grown on GaN templates decreases and the surface roughness of the samples increases.V-pits and trench defects were not found in the AFM images.p++-GaN/InGaN/n++-GaN TJs were investigated for various In content,InGaN thicknesses and doping concentration in the InGaN insert layer.The InGaN insert layer can promote good interband tunneling in GaN/InGaN/GaN TJ and significantly reduce operating voltage when doping is sufficiently high.The current density increases with increasing In content for the 3 nm InGaN insert layer,which is achieved by reducing the depletion zone width and the height of the potential barrier.At a forward current density of 500 A/cm^(2),the measured voltage was 4.31 V and the differential resistance was measured to be 3.75×10^(−3)Ω·cm^(2)for the device with a 3 nm p++-In_(0.35)Ga_(0.65)N insert layer.When the thickness of the In_(0.35)Ga_(0.65)N layer is closer to the“balanced”thickness,the TJ current density is higher.If the thickness is too high or too low,the width of the depletion zone will increase and the current density will decrease.The undoped InGaN layer has a better performance than n-type doping in the TJ.Polarization-engineered tunnel junctions can enhance the functionality and performance of electronic and optoelectronic devices.
文摘设计了中心波长为520 nm的AlGaInN/InGaN应变补偿分布布拉格反射镜(DBR)结构,通过调节组分参数实现应变补偿,使DBR整体应变为0,采用传输矩阵法,计算了Al_(0.7)Ga_(0.3-x)In x N/InGaN DBR、Al_(0.8)Ga_(0.2-x)In x N/InGaN DBR、Al_(0.9)Ga_(0.1-x)In x N/InGaN DBR的反射光谱。通过对DBR结构参数进行对比,优化了其结构和反射性能。首先对比高低折射率层生长顺序,发现对于Al_(0.8)Ga_(0.14)In_(0.06)N/In_(0.123)Ga_(0.877)N DBR,先生长高折射率层时,反射率高达99.61%,而先生长低折射率层时,反射率仅为97.73%;然后对比奇数层DBR和偶数层DBR,发现两者的反射谱几乎重合,没有显著区别;通过研究DBR对数对反射率的影响,发现对数在20~30对时,反射率随着对数的增加明显上升,30~40对时反射率增长缓慢;最后研究了材料组分对反射谱的影响,发现Al组分高的DBR折射率差大,反射性能更优,而相同Al组分的AlGaInN中In含量越低反射率越高。考虑到DBR制备过程中可能出现的厚度和组分偏差,模拟了厚度和组分出现偏差时反射谱的变化,发现高低折射率层厚度每增加或减少1 nm,反射谱红移或蓝移4~5 nm;而组分的偏差使高反射带带宽和中心波长处反射率发生明显变化。本文的研究为AlGaInN/InGaN DBR的设计和制备提供了一定的理论参考。
文摘为探究不同铟(In)组分In_(x)Ga_(1-x)N势垒对绿光激光二极管光电性能的影响,本文采用SiLENSe(simulator of light emitters based on nitride semiconductors)仿真软件对一系列具有不同In组分In_(x)Ga_(1-x)N势垒的激光二极管进行研究,结果发现In_(x)Ga_(1-x)N势垒中In组分最佳值为3%,此时结构的斜率效率最高,内部光学损耗最低,光学限制因子最大,性能最优。在具有In_(0.03)Ga_(0.97_N势垒的多量子阱结构基础上,设计了一种组分阶梯(composition step-graded,CSG)InGaN势垒多量子阱结构,提高了激光二极管的斜率效率和电光转换效率,增加了光场限制能力。仿真结果表明,当注入电流为120 mA时,具有CSG InGaN势垒的多量子阱结构,电光转换效率从17.7%提高至19.9%,斜率效率从1.09 mW/mA增加到1.14 mW/mA,光学限制因子从1.58%增加到1.62%。本文的研究为制备高功率GaN基绿光激光二极管提供了理论指导和数据支撑。
基金the National Natural Science Foundation of China(Grant No.62074120)the State Key Laboratory on Integrated Optoelectronics(Grant No.IOSKL2018KF10)the Fundamental Research Funds for the Central Universities(Grant No.JB211108).
文摘The nano-patterned InGaN film was used in green InGaN/GaN multiple quantum wells(MQWs)structure,to relieve the unpleasantly existing mismatch between high indium content InGaN and GaN,as well as to enhance the light output.The different self-assembled nano-masks were formed on InGaN by annealing thin Ni layers of different thicknesses.Whereafter,the InGaN films were etched into nano-patterned films.Compared with the green MQWs structure grown on untreated InGaN film,which on nano-patterned InGaN had better luminous performance.Among them the MQWs performed best when 3 nm thick Ni film was used as mask,because that optimally balanced the effects of nano-patterned InGaN on the crystal quality and the light output.
基金This work was supported by the National Natural Science Foundation of China(Nos.U21A20493,62104204,and 62234011)the National Key Research and Development Program of China(No.2017YFE0131500)the President’s Foundation of Xiamen University(No.20720220108).
文摘Room temperature low threshold lasing of green GaNbased vertical cavity surface emitting laser(VCSEL)was demonstrated under continuous wave(CW)operation.By using self-formed InGaN quantum dots(QDs)as the active region,the VCSEL emitting at 524.0 nm has a threshold current density of 51.97 A cm^(-2),the lowest ever reported.The QD epitaxial wafer featured with a high IQE of 69.94%and theδ-function-like density of states plays an important role in achieving low threshold current.Besides,a short cavity of the device(~4.0λ)is vital to enhance the spontaneous emission coupling factor to 0.094,increase the gain coefficient factor,and decrease the optical loss.To improve heat dissipation,AlN layer was used as the current confinement layer and electroplated copper plate was used to replace metal bonding.The results provide important guidance to achieving high performance GaN-based VCSELs.
基金supported by the Swedish Research Council (VR),the Foundation for Strategic Research (SSF),the Knut and Alice Wallenberg foundation (KAW),the Swedish Energy Agency and Sweden’s innovation agency (VINNOVA)。
文摘Miniaturization of light-emitting diodes(LEDs) with sizes down to a few micrometers has become a hot topic in both academia and industry due to their attractive applications on self-emissive displays for high-definition televisions,augmented/mixed realities and head-up displays, and also on optogenetics, high-speed light communication, etc. The conventional top-down technology uses dry etching to define the LED size, leading to damage to the LED side walls.Since sizes of microLEDs approach the carrier diffusion length, the damaged side walls play an important role, reducing microLED performance significantly from that of large area LEDs. In this paper, we review our efforts on realization of microLEDs by direct bottom-up growth, based on selective area metal–organic vapor phase epitaxy. The individual LEDs based on either GaN nanowires or InGaN platelets are smaller than 1 μm in our approach. Such nano-LEDs can be used as building blocks in arrays to assemble microLEDs with different sizes, avoiding the side wall damage by dry etching encountered for the top-down approach. The technology of InGaN platelets is especially interesting since InGaN quantum wells emitting red, green and blue light can be grown on such platelets with a low-level of strain by changing the indium content in the InGaN platelets. This technology is therefore very attractive for highly efficient microLEDs of three primary colors for displays.
