在砷化鎵基板上成長應變之銻砷化鎵與其對表面砷化銦奈米結構的影響之研究

Abstract

本實驗是將3 ML InAs 奈米結構成長在緩衝層GaAsSb / GaAs上，主要研究緩衝層GaAsSb隨著厚度的變化，其應變與組成成分的變化，並觀察其上的InAs奈米結構的表面型態。 因此，首先，由倒空間圖譜 (RSM) 的分析，使我們知道隨著緩衝層GaAsSb厚度的增加，其鬆弛程度與銻的峰值含量也隨之增加。再者，由拉塞福回向散射 (RBS) 分析，使我們發現緩衝層GaAsSb的銻含量是呈現出漸增式 (grading) 的分佈。甚至，由離子溝道效應 (Ion Channeling Effect) 分析，讓我們了解到在樣品中不同位置的元素，如表面的銻與深層的銻，其所受的應力也不同，如深層的銻大於表面的銻。最後，由原子力顯微鏡 (AFM) 分析，讓我們觀察到樣品表面的InAs奈米結構的分佈型態：(1) 隨機分佈，(2) 在田埂狀 (cross-hatching) 的表面上選擇性的成長，(3) 奈米結構漸漸地消失，最後僅剩田埂狀的表面型態。

In this experiment, 3 monolayers of InAs is grown on top of a GaAsSb buffer layer on the GaAs substrate. We investigate the changes of strain and composition of the GaAsSb buffer layers with various thicknesses. The surface morphology of the InAs nanostructure is also studied. Reciprocal space mapping (RSM) shows that the relaxation degree and the peak Sb composition of the GaAsSb layer increase with increasing the GaAsSb thickness. Rutherford backscattering spectrometry (RBS) further reveals the grading profile of the Sb content in the GaAsSb layer. Ion channeling effect provides the information that the elements located at different vertical positions in the GaAsSb layer are subject to different stresses, for example, the stress for the Sb deep in the bulk being stronger than near the surface. Atomic force microscopy (AFM) is used to examine the surface morphology of the 3-monolayer InAs. It’s found that the evolution of surface morphology with increasing the GaAsSb thickness can be classified into 3 stages: random distribution of InAs quantum dots, space-selective growth of InAs quantum dots on cross-hatching surface, and purely cross-hatching surface.