本研究主要分為兩個部分，第一部分的樣品系統為氮化鎵磊晶薄膜，第二部分的樣品系統為氮化銦鎵多層量子阱，分別以X光繞射技術對樣品系統做微結構的分析。
首先以傳統X光繞射，從微結構的觀點探討：cubic-GaN / GaAs(001) 磊晶薄膜，隨著Ga流量比的不同，為何呈現不同的發光效益？ 我們測得Ga流量比為0.8的樣品，所成長的cubic-GaN的磊晶薄膜品質最差，連帶導致較差的發光效益；然而，在Ga流量比介於0.8~1.2所成長的cubic-GaN，晶格常數並無實驗可察覺的變化；但薄膜中伴生的wurtzite雜相，隨著Ga流量比增加而有晶格常數c增大的趨向。推測在Ga流量比大於1.0的樣品中，多餘的Ga原子形成類似雜質插入型進占的缺陷結構。此外，若雜相的結晶性較好，薄膜整體受到較大的應力，使發光效益因而變差。導致雜相主要的成因為疊差和孿晶，經由方位球面，可清楚標定wurtzite雜相在cubic-GaN磊晶薄膜中成長的幾何關係和晶域分佈。

其次利用同步輻射X光高解析繞射的方法，來鑑定InXGa1-XN 多層量子阱的超晶格結構。經由線性彌合分析，精確定出量子阱中的雙層周期厚度和銦的含量值x，並和樣品製備的設計值做一比較。

In this work we use X-ray diffraction to analyze the microstructures of two III-nitride sample systems. The first part of sample systems is cubic-GaN epilayers MBE-grown on GaAs(001) of assorted Ga flux ratio from 0.8, 1.0, 1.1, to 1.2; the second part is the InxGa1-xN-GaN multiple quantum wells on sapphire, varied with the fractional molar value of In- composition: x = 0.1~0.25, nominally.
Starting from the focus of polytype GaN as revealed by conventional X-ray diffraction, we derive a correlation of the light-emitting efficiency with different Ga flux ratio to the crystalline quality of microstructures. It is simply confirmed that the Ga-poor sample of Ga flux ratio 0.8 shows worse quality both on the emission peak of 380-nm photoluminescence and on the diffraction width of zinc-blende crystalline structures. While, after a rigorous examination on the purposed cubic-GaN films from Ga-poor to Ga-rich, we do not resolve any difference in the lattice constants. On the other side, the lattice constant c of the wurtzite phases mixed in the GaN film gradually expands as the Ga flux ratio getting increased. We conjecture that, in Ga-rich samples, extra Ga atoms would occupy the interstitial sites in wurtzite domains to play a role as impurity-like defects. Consequently, as if the wurtzite domains had a better crystalline quality, the overall thin film would suffer more stress and yield a worse efficiency in the light emission. In view of the orientation spheres, the geometric correlation and domain distributions of the primary and twined wurtzite phases are properly reconstructed with respect to the cubic-GaN lattice. We conclude that the origin of wurtzite domains is due to the stacking fault and twin bands prevailing in the GaN film.

Following after the study of GaN epilayers, but taking advantage of bright and well-collimated synchrotron X-rays, we apply high-resolution X-ray diffraction to characterize the superlattice structure of InxGa1-xN multiple quantum wells. Preliminary results have been done to precisely determine the thickness of periodic InxGa1-xN-GaN bilayers and to assure the indium composition as compared with the nominal value x. All of our analyses are straightly based upon a linear regression from the peak positions of superlattice reflections, which is less dependent of the details presumed in a strain-layer model.

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