隨著互補式金氧半場效電晶體(MOSFETs)擔子元件尺寸的縮小,現有的矽半導體相關的電子元件已面臨本質材料與技術上的挑戰,因此現在具備高載子遷移率之半導體材料成為發展趨勢,利用高介電係數氧化物例如氧化鋁、氧化鉿,搭配高載子三五族半導體例如砷化鎵,都是非常有潛力或著是已經準備量產的互補式金氧半場效電晶體。 了解氧化物和三五族半導體的界面特性,並且進一步去改善電性表現,是了解互補式金氧半場效電晶體最重要的議題。本實驗利用原子層沉積法(ALD)成長高介電係數氧化鋁及氧化鉿於乾淨的砷化鎵半導體上,利用X-ray光電子能譜(XPS)分析界面的化學鍵結特性,利用掃描穿隧試顯微鏡(STM)呈現原子級的表面情形,以上過程中皆在超高真空系統中進行,最後再製成MOSCPA分析電性結果。 本實驗共分三部分,第一部分在探討砷化鎵重構的表面,分別為As-rich(2x4)以及Ga-rich(4x6),Ga-rich的重構表面在C-V曲線和Dit有比較好的電性結果,配合XPS界面化學分析得到AsOx和Ga-O-Al扮演很重要的因素影響電性。第二部分,試著成長不同厚度的氧化鋁(14、8、5和3nm)在砷化鎵(4x6)表面,我們都得到非常好的電性表現,不過5nm厚度氧化鋁經過550oC一小時退火後,XPS觀察到Ga3+和AsOx出現在氧化物和半討體界面,這會使漏電流大幅的增加。第三部分,成長氧化鉿在砷化鎵表面上,討論利用TMA當作催化劑是否有效改善界面得到較好的電性表現,結果在不破真空的情形下(in-situ),無論是否有多通一層TMA都可以得到較好電性特性。
Understanding the interfacial electronic characteristics of oxide/III-V and improving its electrical properties is one of the most critical issues for realizing the advanced III-V MOS devices. In this work, the growth of atomic-layer-deposition (ALD) onto fresh molecular-beam-epitaxy (MBE) grown GaAs epi-layer, uses XPS to interface chemical analysis and fabricate MOS capacitors for electrical properties research. In the first part, Al2O3 on GaAs (001) are used with two different reconstruction surfaces: As-rich (2×4) and Ga-rich (4×6). Both the C-V curve and Dit values show better behavior on Ga-rich surfaces than with As-rich surface samples. Based on the results of electrical measurement and XPS analysis, the amounts of AsOx and Ga-O-Al/Ga1+ play an important role in affecting the electrical properties. In the second part, varying the thickness (14, 8, 5, and 3nm) of ALD-Al2O3 on GaAs(001)-(4×6) obtained good electrical characteristics. The leakage current increased after the annealing of 5nm thickness Al2O3. XPS found that Ga3+ and AsOx were diffused to the oxide surface after RTP annealing at 550oC. Therefore, the growth of hetro-structures of Al2O3/ GaAs with thinner oxide has a difficulty in GaAs devices. In part three, we researched properties of HfO2/GaAs interfaces with TMA exposure. The result showed that high-quality interfacial characteristics were attained by in-situ ALD-HfO2 passivation on GaAs surfaces, however the TMA exposure is not a strong difference for HfO2 in-situ growth on GaAs surfaces.