摘要
AlGaN是制备深紫外光电器件和电子器件的重要材料.随着Al组分的增加,AlGaN材料表面容易出现局域组分不均匀的相分离现象,进而影响器件的性能.为了探索相分离的微观机制,本文采用了同位的共聚焦微区荧光光谱和扫描开尔文探针显微术对不同Al组分的AlGaN表面相分离现象进行了表征.三片样品的Al组分比分别约为0.3,0.5和0.7.本文采用的基于双频锁相的单次扫描开尔文探针显微术,可获得高空间分辨(约10 nm)的表面电势像.在微区荧光光谱中出现明显相分离现象的区域,利用此方法获得的表面电势像可以清晰地观察到犬牙交错的台阶及其表面凹坑边缘的电势变化,对应组分的不均匀性.随着台阶转入台阶流的形态,表面凹坑逐渐缩小和合并,台阶和凹坑边缘不再出现明显的电势畴界,光谱中相分离的现象消失.实验结果表明,AlGaN表面的台阶和凹坑边缘是产生组分不均匀性,进而在光谱中产生相分离现象的主要原因;结合同位微区荧光光谱,高分辨的扫描开尔文探针显微术是一种有效的表征AlGaN相分离微观机制的方法.
AlGaN is a key material for deep ultraviolet optoelectronic and electronic devices.With the increase of the Al composition ratio,the phase separation on the surface,caused by small-scale compositional fluctuations,is prone to affecting the performance of the device.In order to explore the mechanism of the phase separation on a nanoscale,the AlGaN wafers with different quantities of Al compositions are investigated by the confocal photoluminescence spectroscopy and the single-pass Kelvin force probe microscopy.The composition ratios of Al for the three samples are about 0.3,0.5,and 0.7,respectively.The single-pass Kelvin force probe microscopy based on dual-frequency phase-locking is used to obtain high spatially resolved(about 10 nm)surface potential images.In the area where the phase separation phenomenon is obvious in the photoluminescence spectrum,the sharp change of the surface potential can be observed at the irregular steps and the edges of the surface pits.The potential changes can be ascribed to the inhomogeneous composition distribution.In the area where the topography turns into step flow,the surface pits shrink and merge.No obvious surface potential domain boundaries appear at the steps nor on the edges of the surface pits.Meanwhile,the phase separation phenomenon in the photoluminescence spectrum almost disappears.Our experiments show that the steps and the edges of the surface pits on AlGaN surfaces are main reasons for small-scale compositional fluctuations and the phase separation in the spectrum.Combining with in-situ confocal photoluminescence spectra,high spatially resolved surface potential image by single-pass Kelvin force probe microscopy is an effective method to characterize the phase separation on AlGaN surface on a nanoscale.
作者
刘博阳
宋文涛
刘争晖
†孙晓娟
王开明
王亚坤
张春玉
陈科蓓
徐耿钊
徐科
黎大兵
Liu Bo-Yang;Song Wen-Tao;Liu Zheng-Hui;Sun Xiao-Juan;Wang Kai-Ming;Wang Ya-Kun;Zhang Chun-Yu;Chen Ke-Bei;Xu Geng-Zhao;Xu Ke;Li Da-Bing(School of Nano-Tech and Nano-Bionics,University of Science and Technology of China,Hefei 230026,China;Suzhou Institue of Nano-Tech and Nano-Bionics,Chinese Academy of Sciences,Suzhou 215123,China;Nano Science and Technology Institute,University of Science and Technology of China,Suzhou 215123,China;Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,Changchun 130033,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第12期124-132,共9页
Acta Physica Sinica
基金
国家重点研发计划(批准号:2016YFB0400101)
国家自然科学基金(批准号:11804369)
中国科学院关键技术人才资助的课题。
关键词
铝镓氮
相分离
扫描开尔文探针显微术
荧光光谱
AlGaN
phase separation
Kelvin force probe microscopy
photoluminescence spectroscopy
