鍺的電子和電洞遷移率分別為矽的三倍和四倍，因此是下一世代被用來取代矽元件中的通道層。但是自然形成的二氧化鍺熱穩定性差且溶於水，並不適合用在金氧半場效電晶體的製程。故利用高介電係數的氧化層取代二氧化鍺來改善元件的電子特性。在本次的工作中，使用分子束磊晶成長Ga2O3(Gd2O3)混合氧化物（GGO）、氧化鋁（Al2O3）生長在鍺晶圓上。利用X光光電子能譜分析儀和穿遂式電子顯微鏡來分析氧化物的特性以及氧化物和半導體間介面的電子結構。我們發現經過400oC超高真空加熱表面處理，可去除鍺表面自然生成的氧化物。
在分子束磊晶方面，由TEM也可看出氧化層和半導體間無額外的二氧化鍺界面層產生，而且氧化物在高溫製程中仍能保有高度非結晶性，這有助於縮小積體電路線寬和應用在實際元件製程。XPS則分析出氧化物和半導體界面相互反應的情況。電性方面，分子束磊晶成長GGO的介電常數為14.5，低漏電流為2×10-9 A/cm2。界面間的能量態密度經由Terman method計算約為2x1012 cm-2eV-1。

Germanium with its electron and hole mobility almost three and four times of those in Silicon, respectively, is now being considered as a high mobility channel to replace Si. However, the native oxides due to their poor thermal stability have been attributed to insufficient passivation of the Ge surface, which has hindered the fabrication of Ge metal oxide semiconductor field effect transistor (MOSFET). High-κ dielectrics were used to replace native Ge oxides to improve the electrical properties. In the present work, two high-κ dielectrics as Ga2O3 (Gd2O3) mixed oxide (GGO), Al2O3 grown by molecular beam epitaxy (MBE) have been deposited on a germanium substrate. The oxide/Ge interfaces were analyzed using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). By them, we have found that the native oxides can be removed with the annealing temperatures up to 400□C.
The GGO and Al2O3 deposited by our multi-chamber MBE system can effectively passivate the Ge surface without forming an interfacial layer of GeO2 according to the HRTEM pictures. The robustness of the interface is the cornerstone for further device fabrication and scaling. Those oxides also show high thermal stability of oxide and interface. The leakage current density of MBE grown GGO is 2×10-9 A/cm2 with the κ value 14.5. The interface trap density calculated by the Terman method is 1x1012 cm-2eV-1 near the midgap.

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