磊晶成長高品質鍺薄膜於砷化鎵基板之研究

Abstract

隨著傳統矽半導體元件不斷的以縮小尺寸，達到節省成本與加速運算速率的目標已漸漸遇到瓶頸，如:漏電流的提高、通道傳導速率的降低。為解決問題，科學家便開始尋求其他材料來代替傳統的矽，擁有高速電子傳導率的三五族複合物馬上就受到科學家的注意，但是為了要提升互補式金氧半元件的效率，擁有高速電洞傳導率的鍺材料也受到相當的重視。 本實驗是將鍺薄膜磊晶成長於砷化鎵基板上，利用改變成長溫度、壓力等因素來使成長出的鍺薄膜擁有良好的特性，從材料分析裡可以了解鍺薄膜磊晶在砷化鎵基板後的結晶性、是否有缺陷存在，以及鍺薄膜的表面平整度，接著從螢光光譜儀與載子濃度分析儀的結果發現，我們的結構在螢光光譜儀產生峰值，並且從載子濃度分析儀得知鍺薄膜有從砷化鎵基板自體擴散的砷與鎵原子，最後使得結構為n-type，未來我們成長的高品質鍺薄膜於砷化鎵基板上可以應用於的互補式金氧半導體元件的整合，以提升整體的效率。

The practice of scaling in microelectronics has allowed constant improvements in the cost, performance, and functionality of Si-based integrated circuits. However, as feature size is below 100nm, the performance improvement attribute to scaling is diminished. At first, the gate leakage current increases through ultra-thin SiO2. Secondly, channel mobility is degraded in the high electrical field. III-V compounds have attracted lots of attention because of their high electron mobility. However, III-V materials still suffer from low hole mobility, and it is very important to find a new material with high hole mobility to extend their performance towards the applications of complementary metal-oxide-semiconductor (CMOS) devices. Ge attracted lots of attentions because of its high hole mobility. In this study, high-quality epitaxial Ge film was deposited on GaAs substrate by ultrahigh vacuum chemical vapor deposition (UHVCVD). Take different growth factors into account to deposit high quality Ge epitaxial layer on GaAs substrate. In-depth characterizations of Ge film structure, optical and electrical properties, and doping conditions were carried out by x-ray diffraction (XRD), cross-sectional transmission electron microscopy (TEM), scanning electron microscope (SEM), atomic force microscopy (AFM), photoluminescence (PL), and electrochemical capacitance voltage (ECV) profiling. In the end, the Ge epitaxial film is n-type with a donor concentration generated by self-doping. It reveals that the electrons in L valley recombine with holes in the valence band, and appearance of the direct band gap emission in the Ge epitaxial film on GaAs substrate. This high quality n-type Ge epitaxial film can be used for the fabrication of p-channel MOSFET, and useful for the future integration of Ge p-channel and GaAs n-channel electronic devices on Si template.