SCANNING CATHODOLUMINESCENCE MICROSCOPY - A UNIQUE APPROACH TO ATOMIC-SCALE CHARACTERIZATION OF HETEROINTERFACES AND IMAGING OF SEMICONDUCTOR INHOMOGENEITIES
SCANNING CATHODOLUMINESCENCE MICROSCOPY - A UNIQUE APPROACH TO ATOMIC-SCALE CHARACTERIZATION OF HETEROINTERFACES AND IMAGING OF SEMICONDUCTOR INHOMOGENEITIES
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DOI：
10.1116/1.585704
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发表时间：
1991-07-01
影响因子：
1.4
通讯作者：
BIMBERG, D
中科院分区：
文献类型：
--
作者：
CHRISTEN, J;GRUNDMANN, M;BIMBERG, D
发光实验提供了一个强大的和非破坏性的方法，非原位调查半导体异质界面，可能会被埋到几个μ m以下的表面在一个给定的复杂的样品结构。 结合简单地通过在整个研究区域上扫描激发聚焦电子束来拍摄图像的能力，可以通过扫描阴极发光（CL）直接可视化电子性质的横向波动，如基本带隙E（g）（x，y）的变化。 新的实验方法，阴极发光波长成像（CLWI），涉及在每个扫描位置（x，y）记录完整的CL光谱，产生量子威尔斯（QW）的原子尺度形态的直接3D图像，如QW激子所感测的：类似于扫描隧道显微镜的尖端，激子对QW厚度L（z）的局部波动进行采样并将该结构信息L（z）（x，y）转换为光谱信息，带隙E（g）（x，y），从而CL发射波长-λ-（x，y）。 因此，量子阱界面的拓扑图可以在不同的位置和不同的放大率下被记录。 界面粗糙度可以在横向分辨率上进行统计研究，从量子阱激子的直径开始到mm制度。 记录λ-（x，y）和E（g）（x，y）图的相同实验原理成功地应用于图案化结构的分析。 在非晶格匹配的GaAs/Si系统中，横向应变的变化引起E（g）（x，y）涨落，因此可以直接用CLWI成像。 在微图案化Si（001）衬底上金属有机化学气相沉积生长的GaAs层显示出强烈的Si杂质不均匀掺杂。 通过CLWI的强烈增加，这硅掺入附近的自由{111}表面的测量和硅浓度图记录在整个样品图案。
Luminescence experiments provide a powerful and nondestructive approach to the ex situ investigation of semiconductor heterointerfaces which might be buried up to several mu-m below the surface in a given complex sample structure. Combined with the ability of taking images simply by scanning the exciting focused electron beam across the area under investigation, lateral fluctuations of electronic properties like the variation of the fundamental band gap E(g) (x,y) can be directly visualized by scanning cathodoluminescence (CL). The novel experimental approach, cathodoluminescence wavelength imaging (CLWI), which involves recording of a complete CL spectrum at every scanning position (x,y), yields direct 3D images of the atomic-scale morphology of quantum wells (QWs) as sensed by the QW exciton: similar to the tip of a scanning tunneling microscope, the exciton samples the local fluctuations of QW thickness L(z) and transforms this structural information L(z) (x,y) into a spectral one, the lateral variation of band gap E(g) (x,y) and thus the CL emission wavelength-lambda-(x,y). Topological maps of QW interfaces can thus be recorded at various positions and at various magnifications. The interface roughness can be investigated statistically at lateral resolution starting with the diameter of the QW exciton up to the mm regime. The same experimental principle for recording lambda-(x,y) and E(g)(x,y) maps is successfully applied for the analysis of patterned structures. In the nonlattice-matched system GaAs on Si, the lateral strain variation causes E(g)(x,y) fluctuations and can thus be directly imaged by CLWI. Metalorganic chemical vapor deposition grown GaAs layers on micropatterned Si(001) substrates show strongly inhomogeneous doping with Si impurities. By means of CLWI the strong increase of this Si incorporation in the vicinity of free {111} surfaces is measured and Si concentration maps are recorded across the complete sample pattern.