Interfacial Mixing Analysis for Strained Layer Superlattices by Atom Probe Tomography
Interfacial Mixing Analysis for Strained Layer Superlattices by Atom Probe Tomography
复制标题
通过原子探针断层扫描对应变层超晶格进行界面混合分析
作者：
A. Rajeev;Weixin Chen;J. Kirch;S. Babcock;T. Kuech;T. Earles;L. Mawst
具有精确厚度和界面处成分突变的量子阱和势垒对于从量子级联激光器件获得所需的发射波长至关重要。高分辨率 X 射线衍射和透射电子显微镜通常用于校准和表征层的厚度和成分。这里采用了一种补充技术，即原子探针断层扫描，来直接测量两个 InxGa1−xAs/InyAl1−yAs III-V 应变层超晶格结构（均在 605 °C 下生长）的 3 维空间分辨成分分布。将测得的成分分布与菲克第二定律的解进行拟合，得出 605 °C 时的平均相互扩散系数为 3.5 × 10−23 m2 s−1。针对这些特定超晶格确定的每层相互扩散程度平均为 0.55 nm。结果表明，在通常为量子级联激光器件设计的厚度和生长方案的结构中，将形成四元活性层，而不是预期的三元化合物。
Quantum wells and barriers with precise thicknesses and abrupt composition changes at their interfaces are critical for obtaining the desired emission wavelength from quantum cascade laser devices. High-resolution X-ray diffraction and transmission electron microscopy are commonly used to calibrate and characterize the layers’ thicknesses and compositions. A complementary technique, atom probe tomography, was employed here to obtain a direct measurement of the 3-dimensional spatially-resolved compositional profile in two InxGa1−xAs/InyAl1−yAs III-V strained-layer superlattice structures, both grown at 605 °C. Fitting the measured composition profiles to solutions to Fick’s Second Law yielded an average interdiffusion coefficient of 3.5 × 10−23 m2 s−1 at 605 °C. The extent of interdiffusion into each layer determined for these specific superlattices was 0.55 nm on average. The results suggest that quaternary active layers will form, rather than the intended ternary compounds, in structures with thicknesses and growth protocols that are typically designed for quantum cascade laser devices.