以液相磊晶法改善砷化鎵晶體品質

Improving The Crystal Qualities of Gallium Arsenide by Liquid Phase Epitaxy

羅健倫(Chien-Lun Lo)

指導教授 ： 温武義

中原大學/電機資訊學院/電子工程研究所/碩士(2018年)

https://doi.org/10.6840/cycu201800460

摘要

幾十年來，半導體元件的進步非常迅速，隨著矽IC元件摩爾定律的發展預測已達其極限，早已有其他替代矽的半導體材料被研究探討著，其中屬於三五族化合物的砷化鎵有著多項優點，例如:較矽高的遷移率、直接能隙(可用於發光元件如LED等)，在高速元件及高效率太陽能電池方面遠較矽有應用價值。然而砷化鎵目前不像矽可以低成本且來源不虞匱乏，尤其對台灣而言，砷化鎵晶片品質與貨源掌握不易，而探討砷化鎵晶片重複使用的可能性也自然變成一個重要課題。因此，如何以簡易經濟的方法製備品質改善且達一定厚度以上的砷化鎵薄膜於現有GaAs基板上是頗具意義的。
因此，本研究中我們使用液相磊晶(Liquid Phase Epitaxy, LPE)法來製備砷化鎵同質磊晶薄膜，藉此改善磊晶基板的品質以供後續更加應用。磊晶過程中使用鎵作為溶媒，並藉由調整成長溶液飽和溫度、不同降溫方式與速率來尋求砷化鎵磊晶優化參數。對於磊晶層我們使用光學顯微鏡觀察其表面形態，並利用溶融KOH蝕刻樣品呈現蝕刻孔以計算蝕刻孔密度(Etch Pit Density, EPD)方式來鑑定品質。一般砷化鎵基板的缺陷密度大約是105cm-2，而經過LPE磊晶後發現可降至103cm-2，有兩個數量級的改善。

關鍵字

液相磊晶 ； 降溫成長 ； 砷化鎵 ； 鎵 ； 光學顯微鏡 ； 掃描式電子顯微鏡 ； X-射線繞射分析 ； 光激螢光光譜 ； 缺陷密度

並列摘要

In the past decades, the progress of semiconductor devices has been very rapid. As the development of the Moore's Law for Si IC devices has reached its limit, other semiconductor materials that have already replaced Si have long been studied and explored, among which gallium arsenide belonging to the Group III compound has several advantages, such as: higher mobility, direct energy gap (can be used for light-emitting components such as LEDs, etc.), in the high-speed components and high-efficiency solar cells are far more valuable than Si. However, gallium arsenide is currently not as cheap as Si and its source is scarce. For Taiwan, in particular, gallium arsenide wafer quality and source control are not easy to grasp, and the possibility of reusing gallium arsenide wafers has naturally become an important issue. Therefore, it is meaningful to prepare a thick enough gallium arsenide thin film having a good quality on a conventional GaAs substrate by a simple and economical method.
Therefore, in this study, we use liquid phase epitaxy (LPE) method to prepare gallium arsenide homogeneous epitaxial thin films, thereby improving the quality of epitaxial substrates for further applications. In the epitaxial process, Ga is used as a solvent, and the gallium arsenide epitaxial optimization parameters are sought by adjusting the saturation temperature of the growth solution, different cooling methods and rates. For the epitaxial layer, we used an optical microscope to observe the surface morphology and etch the sample using a molten KOH to form etch pits and calculate the etch pit density (EPD) to identify the quality. The defect density of a typical gallium arsenide substrate is about 105 cm-2, and it can be reduced to 103 cm-2 after LPE epitaxy, which is an improvement of about two orders of magnitude.

並列關鍵字

Liquid phase epitaxy ； Cooling Growth ； GaAs ； Optical Microscope ； The Scanning Electron Microscope ； X-ray Diffraction Analysis ； Photoluminescence ； Gallium ； EPD

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