成長在砷化鎵基板之銻磷化鎵結構特性以及德拜-沃勒因子研究

Abstract

我們利用金屬有機物化學氣相沉積在砷化鎵基板上成長銻磷化鎵，包含兩種鍵長相異甚大的合金磷化鎵和銻化鎵，將這種高度不匹配的原子填充到晶格中會導致強烈的鍵結扭曲，將會導致成長上的困難，因此產生兩片單一相以及一片相分離的樣品。我們進行X光繞射在對稱面上的量測，在雙軸應變相同的前提下，利用布拉格公式和維加德定律計算出單一相樣品的組成成分之濃度，再透過非對稱面的量測，將相分離中較靠近基板峰的相解析出來並計算成分比例，接著我們針對相分離的樣品進行能量色散X射線譜和電子微探儀的量測，判斷相分離中哪一個相含量較高，並與X光繞射強度進行比較。 於國家同步輻射中心量測磷和銻延伸X光吸收精細結構，並且透過Athena和Artemis軟體分析擬合，可以分別得到三個樣品中磷化鎵和銻化鎵的鍵長，並且跟價力場模型中利用1000顆原子模擬出來的結果進行比較。最後利用X光繞射的強度計算原子偏差，歷史上德拜提出了一個理論來解釋為什麼晶體中原子的熱擾動不會影響X光繞射的半高寬，相反其只影響其強度，德拜將此歸因於熱擾動的零平均值，然而強度卻與德拜-沃勒因子成正比，此因子是原子熱擾動方均根的指數函數，因此我們透過X光繞射的強度比例，經由計算得到得到銻磷化鎵和砷化鎵的原子偏差平方，前者由於鍵結扭曲和熱擾動而具有強烈的偏差，而後者僅由於熱擾動而具有偏差。

We use metalorganic chemical vapor deposition to grow gallium phosphide antimonide on gallium arsenide substrates, including two alloys of gallium phosphide and gallium antimonide, which have very different bond lengths. So, it is a highly mismatched alloy. This can result in strong bond distortions that can cause growth difficulties, resulting in two single phases and one phase separation sample. We perform the measurement of the X-ray diffraction on the symmetry plane. Suppose that biaxial strain, the concentration of the composition of the single-phase sample is calculated by the Bragg formula and Vegard's law. Then the measurement through the asymmetric plane is performed, in order to analyze the phase closer to the substrate peak in the phase separation and calculate the composition ratio. Then we measure the energy dispersive X-ray spectrum and the electronic microprobe for the phase separation sample to determine which phase in the phase separation is higher. which compared to with the X-ray diffraction intensity. The X-ray absorption fine structure of phosphorus and antimony was measured at NSRRC, and the bond lengths of gallium phosphide and gallium antimonide in three samples were obtained by Athena and Artemis software analysis fitting, respectively, compared to VFF model of 1000 atoms simulation. Finally, the atomic deviation is calculated by the intensity of X-ray diffraction. In history, Debye proposed a theory to explain why the thermal vibration of atoms in the crystal does not affect the full width at half maximum. Instead, it only affects its intensity, and the intensity is proportional to the Debye-Waller factor, which is an exponential function of the square root of the atom deviation. So, we calculate by the intensity ratio of the X-ray diffraction.