Research for the Fabrication of Light Emitting Diodes with Ultra-high Efficiency

超高效率发光二极管的制作研究

• 批准号: 10355001
• 负责人: FUJITA Shigeo
• 金额: $ 18.69万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A).
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10355001/
• 关键词: Nitride Semiconductors; Low-dimensional Structures; Localized Exciton; Time-space resolved spectroscopy; Radiative Recombination; Non-radiative Recombination; Ultra-high Efficient Emission; InGaN; 短波長発光ダイオード; 輻射再結合; 非輻射再結合; 外部量子効率; 時間分解ホトルミネセン

The objective of this project is to find the key to achieve ultra-highly efficient (η_<ext>>40%) light emitting diodes (LEDs) covering ultraviolet (UV), blue, green and white spectral range. The results obtained in the period of 2000 to 2001 can be summarized as follows.(1) Time-resolved electroluminescence (TREL) was performed in green, blue and near-UV LEDs based on In_xGa_<1-x>N single quantum well structures under pulsed current injection, by which emission mechanism could be assessed in the actual device operation. It was found that EL linewidth as well as Stokes shift was enhanced with increasing mean In composition in active layers due to the increase of exciton (and/or carrier) localization.(2) Time-space resolved photoluminescence (TSRPL) spectroscopy was set up by focusing UV-pulsed laser (wavelength : 266 nm, pulse width : 1.5 ps) in an optical microscope using UV optical components. By using this system, epitaxially lateral overgrown (ELO) GaN was assessed, and site selective photo-excitation was made to either 4 μm-wide window region with threading dislocation density (TDD) of 10^8 cm^<-3>, or 8 μm-wide wing region with TDD of 10^6 cm^<-3>. As a result, PL lifetime in the wing region was slightly larger than that in the window region, indicating that threading dislocations act as nonradiative centers. However, the difference of lifetime was very small considering two-orders difference in TDD.Therefore, it is suggested that pathway to nonradiative recombination is limited by other centers whose origin is probably point defects.(3) TSRPL in air-bridged laterally epitaxial grown (ABLEG) InGaN layers revealed that the addition of small amount of In to active layers results in the enhancement of PL efficiency because of the reduction of nonradiative recombination centers originating from point defects

该项目的目标是找到实现超高效（η_<ext>>40%）发光二极管（led）覆盖紫外（UV），蓝，绿，白光谱范围的关键。2000年至2001年的研究结果总结如下：(1)在脉冲电流注入下，利用In_xGa_<1-x>N单量子阱结构实现了绿色、蓝色和近紫外led的时间分辨电致发光（TREL），从而在实际器件工作中评估其发光机理。发现由于激子（和/或载流子）局域化的增加，EL线宽和Stokes位移随着活性层中平均In成分的增加而增强。(2)利用紫外光学元件，在光学显微镜下聚焦波长为266 nm、脉宽为1.5 ps的紫外脉冲激光，建立了时空分辨光致发光（TSRPL）光谱。利用该系统对外延侧向生长（ELO） GaN进行了评价，并对4 μm宽的窗口区（TDD为10^8 cm^<-3>）和8 μm宽的翼区（TDD为10^6 cm^<-3>）进行了选择性光激发。结果表明，翼区的PL寿命略大于窗区的PL寿命，表明螺纹位错是非辐射中心。然而，考虑到TDD的二阶差异，寿命的差异是非常小的。因此，非辐射复合的途径受到其他中心的限制，这些中心的起源可能是点缺陷。(3)气桥横向外延生长（ABLEG） InGaN层的TSRPL表明，在活性层中加入少量的in可以减少由点缺陷引起的非辐射复合中心，从而提高PL效率

项目成果

Y.Narukawa,Y.Kawakami,Sg.Fujita 他: "Radiative and nonradiative recombination processes in ultraviolet light-emitting diode composed of an In_<0.02>Ga_<0.98>N active layer"Applied Physics Letters. 74・4. 558-560 (1999)

Y.Narukawa、Y.Kawakami、Sg.Fujita 等人：“由 In_<0.02>Ga_<0.98>N 活性层组成的紫外发光二极管中的辐射和非辐射复合过程”应用物理快报 74・4。 558- 560 (1999)

Y.Narukawa, Y.Kawakami, Sg.Fujita et al.: "Radiative and nonradiative recombination processes in ultraviolet light-emitting diode composed of an In_<0.02>Ga_<0.98>N active layer"Applied Physics Letters. 74 4. 558-560 (1999)

Y.Narukawa、Y.Kawakami、Sg.Fujita 等人：“由 In_<0.02>Ga_<0.98>N 活性层组成的紫外发光二极管中的辐射和非辐射复合过程”应用物理快报。

Y.Narukawa,Y.Kawakami,Sg.Fujita 他: "Dimensionality of excitons in lesar-diode structures composed of In_xGa_<1-x>N multiple quantum wells"Physical Review B. 59・15. 10283-10288 (1999)

Y.Narukawa、Y.Kawakami、Sg.Fujita 等：“由 In_xGa_<1-x>N 多量子阱组成的 lesar 二极管结构中激子的维数”物理评论 B. 59・15（1999 年） ）

A.Kaneta,Y.Kawakami,Sg.Fujita 他: "Spatial Inhomogeneity of Photoluminescence in an InGaN-Based LED Structure Probed by Near-Field optical Microscopy Under Illumination-Collection Mode"Japanese Journal of Applied Physics. 40・1. 110-111 (2001)

A. Kaneta、Y. Kawakami、Sg. Fujita 等人：“在照明收集模式下通过近场光学显微镜探测 InGaN 基 LED 结构中的光致发光的空间不均匀性”日本应用物理学杂志 40・1。 110-111（2001）

T.Izumi, Y.Kawakami, Sg.Fujita et al.: "Time-resolved photoluminescence spectroscopy in GaN-based semiconductors with micron spatial resolution"Journal of Luminescence. 87-89. 1196-1198 (2000)

T.Izumi、Y.Kawakami、Sg.Fujita 等人：“具有微米空间分辨率的 GaN 基半导体中的时间分辨光致发光光谱”发光杂志。