本論文研究應用於高功率InAlGaN / GaN 金氧半高電子遷移率電晶體。我們主要會以兩個方向來討論此元件，分別是其作為空乏型及增強型元件的電性表現。
本論文採用四元化合物InAlGaN當作障壁層，主要是因為使用InAlN / GaN 形成異質接面的元件雖然可以具有很強的二維電子氣（2DEG）通道，擁有極佳的電性表現，但是在磊晶的過程中因為InN和AlN的溫度和晶格常數不同造成磊晶不易，也因為銦容易聚集形成銦坑洞造成磊晶缺陷，上述兩項原因造成InAlN / GaN 的元件在承受電壓上先天具有較差的表現，非常容易崩潰。
而採用InAlGaN / GaN 異質接面的元件，藉由減少使用銦元素的比例，除了可以減少銦坑洞造成的磊晶缺陷，也能夠透過加入鎵元素來調整該四元化合物的能隙及晶格常數，在保有與InAlN / GaN 元件差不多電性表現的同時，InAlGaN的元件在電壓承受度上能夠獲得更佳的表現，也更適合高功率元件的應用。
除 了基本的電性分析之外，我們亦對此元件進行一些材料分析，例如使用二次離子質譜（SIMS）以確認氟離子的深度分布，或是利用X射線繞射（XRD）、X射線光電子能譜（XPS）來分析氧化層的化學元素組成，也透過原子力顯微鏡（AFM）和透射電子顯微鏡（TEM）來觀察其粗糙度及厚度。
在當作空乏型元件時，該元件的臨界電壓（VTH）為-4.3 V，開/關電流比為10^9，次臨界擺幅（S.S.）為87 mV /decade，最大啟動電流（Ion）為1135 mA / mm，在1μA/ mm時的擊穿電壓（VBR）為330V，與InAlN/GaN 金氧半高電子遷移率電晶體的擊穿電壓250V相比，約提升了31%，證實其相對InAlN/GaN 金氧半高電子遷移率電晶體在承受電壓上的能力確實有顯著提升。
在增強型元件的部分，我們利用氟離子摻雜來達到增強型，其電性表現上，臨界電壓（VTH）為+1.0 V，開/關電流比為10^9，次臨界擺幅（S.S.）為87 mV /decade，最大啟動電流（Ion）為665 mA / mm，在1μA/ mm時的擊穿電壓（VBR）為420V，證明其作為高功率元件是具有非常大的潛能。

In this thesis, we demonstrate a high performance InAlGaN/GaN MOSHEMT for power applications. We discuss the electrical performance of this device in many aspects, such as depletion-mode device, and enhancement-mode device.
For our device, we use a quaternary compound, InAlGaN, as our barrier layer. The main reason is that although InAlN/GaN heterostructure can possess strong two-dimensional electron gas channel and perfect electrical performance, it suffers from epitaxial difficulty because the InN and AlN have different forming temperature and lattice constants during epitaxial process and epitaxial defects because indium would concentrate and form indium pits. The above two reasons cause InAlN/GaN device has bad ability on dealing with large breakdown field and break down easily. By reducing the indium composition in InAlGaN/GaN heterostructure, we can not only decrease the epitaxial defects due to indium pits but also moderate the lattice constant and bandgap energy by adding Ga into InAlN. Therefore, InAlGaN/GaN heterostructure can possess almost the same great DC performance as InAlN/GaN heterostructure and get larger breakdown voltage than InAlN/GaN heterostructure, which is more suitable for high power applications.
Beside the basic DC and output characteristics analyses, we also perform some material analyses on our device, such as using secondary ion mass spectroscopy (SIMS) to confirm the depth distribution and amount of fluorine ions, using x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) to analyze the chemical element composition of the oxide layer and barrier layer, and using atomic force microscope (AFM) and transmission electron microscopy (TEM) to figure out the surface roughness and structure thickness.
As a depletion-mode device, the device has a threshold voltage (VTH) of -4.3 V, an on/off current ratio of 10^9, a sub-threshold swing (S.S.) of 87 mV/ten times, an on-state current (Ion) of 1135 mA/mm, and the breakdown voltage (VBR) at 1μA/mm is 330 V, which is about 31% improvement comparing with d-mode InAlN/GaN device. As an enhancement-mode device, the device has a threshold voltage (VTH) of +1.0 V, an on/off current ratio of 10^9, a sub-threshold swing (S.S.) of 87 mV/ten times, an on-state current (Ion) of 665 mA/mm, and the breakdown voltage (VBR) at 1μA/mm is 420 V. Compared with InAlN/GaN planar device, all performances have been significantly improved, which shows the great potential for InAlGaN/GaN device as a future high power device.

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