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Study on nonradiative recombination mechanism in widegap semiconductors

宽禁带半导体非辐射复合机理研究

基本信息

批准号：
12450011
负责人：
KAWAKAMI Yoichi
金额：
$ 8.7万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

The purpose of this work is to (1) characterize quantitatively the dynamics of capture processes of excitons and/or carriers injected to active layers in widegap semiconductors, (2) clarify the atomic nature of nonradiative recombination centers and correlate with their electronic states, and (3) develop an atomically controlled growth technology by making positive feedback to the growth conditions taking into account the data obtained at (1) and (2). Many of photo-generated and/or electrically injected excitons/carriers looses their energy by the nonradiative recombination processes. Therefore, the elimination as well as the assessment of such mechanism would lead to the improvement of emission efficiency.In this research project, we have succeeded in the observation of radiation-less processes related to carrier diffusion, and heat generation and diffusion due to nonradiative recombination, by employing transient grating spectroscopy based on third order optical nonlinearity. So far, such observation was difficult in spite of its importance.Moreover, we have developed microscopic heat-detecting spectroscopy by combining transient lens spectroscopy with optical microscopy, by which spatial and temporal measurement of the photo-thermal process was assessed at GaN epilayers with low dislocation density, and generation and diffusion of the heat originating from nonradiative recombination could be estimated quantitatively with a spatial resolution of 3 μm. As a result, it was confirmed that threading dislocations act as nonradiative recombination centers of excitons just after photo-generation.Furthermore, we have set up a scanning near-field optical microscopy, by using an apparatus which is capable of detecting both radiative and nonradiative recombination processes complimentary. We expect the future development of the research because of the improvement of spatial resolution down to from sum-micron to nanoscopic level.

本工作的目的是：（1）定量地表征注入到宽禁带半导体有源层的激子和/或载流子的俘获过程的动力学，（2）阐明非辐射复合中心的原子性质并与它们的电子态关联，以及（3）通过考虑在（1）和（2）。许多光生和/或电注入的激子/载流子通过非辐射复合过程失去它们的能量。因此，消除以及评估这种机制将导致发射效率的提高。在本研究项目中，我们已经成功地观察到的无辐射过程中的载流子扩散，热产生和扩散由于非辐射复合，采用瞬态光栅光谱的基础上的三阶光学非线性。此外，我们将瞬态透镜光谱学与光学显微镜相结合，开发了显微热探测光谱学，通过该光谱学，在低位错密度的GaN外延层上评估了光热过程的空间和时间测量，在3 μm的空间分辨率下，可以定量估计非辐射复合热的产生和扩散。实验结果表明，在光生后，穿透位错是激子的非辐射复合中心。此外，我们还建立了一种扫描近场光学显微镜，该显微镜能够同时检测辐射复合和非辐射复合过程。我们期待未来的研究发展，因为空间分辨率的提高，从亚微米到纳米级。