以晶格分析探討氮化鎵孔洞結構上生長氮化鋁鎵的應變鬆弛行為

Abstract

我們利用晶格面距分析技術研究11個生長在具有高矽摻雜氮化鎵層氮化鎵模板的氮化鋁鎵樣品之晶格常數變化，高矽摻雜氮化鎵層則可以經由電化學蝕刻製作奈米多孔結構，具有應力彈性效果，我們探討這些樣品內氮化鋁鎵層之應力釋放行為。我們發現，各樣品氮化鋁鎵層的頂部和底部之晶格常數差異與應力釋放多寡相符合。多孔隙或檯面結構都會使氮化鎵層中的壓縮應力釋放更多，導致氮化鎵晶格常數a變大，因而在氮化鋁鎵層內產生的拉伸應力更強，如此氮化鋁鎵層應力釋放更多，也就有更高的應變鬆弛百分比。儘管不同樣品的氮化鋁鎵層厚度和鋁濃度稍有不同，但這兩者的變化對氮化鋁鎵層應力釋放的影響不大。

The d-spacing crystal lattice analysis technique is used for studying the lattice constant variations of 11 AlGaN/GaN samples with n+-GaN layers. Through an electrochemical etching process, a GaN porous structure can be fabricated in the n+-GaN layer. In this study, we are mainly concerned with the strain relaxation behaviors of the overgrown AlGaN layers in those samples. The variation of the AlGaN lattice constant difference between the top and bottom of the AlGaN layer is consistent with the strain relaxation variation among different samples. With a porous or mesa structure in a sample, the compressive strains in its GaN layers are more relaxed, leading to larger GaN lattice constants, a, and hence a stronger tensile strain in the overgrown AlGaN layer. A stronger tensile strain in an AlGaN layer results in a stronger relaxation behavior and hence a higher strain relaxation percentage. Although the AlGaN layer thickness and Al content vary among different samples, such a variation does not play a crucial role in determining the strain relaxation in the AlGaN layer.