| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 96 === Abstract
In this thesis, three topics are included. One is the direct band gap Ge1-xSnx alloys simulated by valence band anti-crossing method and nonlocal empirical pseudopotential method and the other is the Si-like (x<0.85) strained Si1-xGex N-MOSFETs mobility calculations which include alloy scattering, phonon scattering and roughness scattering. Lastly, Poly-III-V compound semiconductor was proposed to be used as gate electrode first time.
Part I :
For a long time, group IV semiconductors applied on photoelectric devices have been limited in efficiency by nature indirect band gap. Tensile strained Ge can also be a direct band gap material in theoretical simulations, but not easy to fabricate in practice. However, Ge1-xSnx alloys can form the narrow direct band gap and have been fabricated in the reported experiments successfully. Ge1-xSnx alloys can be applied on infrared optoelectronic applications and may be fabricated new high speed transistors further. In this thesis, chapter 2, energy band structures of Ge1-xSnx alloys are simulated to find the possible direct band gap in group IV semiconductors.
Part II :
Strained silicon is the main stream to produce higher mobility in transistors. However, the reasons of increase mobility in N-MOSFETs are not only split the lower delta 2 subband and higher delta 4 subband but also change some important elements under strain. In this topic, chapter 3, we simulate the mobility of Si on Si1-xGex substrates and Si1-xGex on Si1-xGex substrates N-MOSFETs and include difference kinds of scattering effects.
Part III :
As High-k dielectrics were used to replace conventional SiO2 as insulators of MOSFETs, poly-silicon gate must also been replaced by different kinds of metals. In this topic, chapter 4, ploy-III-V semiconductor was fabricated as gate electrode of metal-oxide semiconductors (MOS) first time. Utilizing band gap of III-V semiconductor can adjust the work function and the results of experiments were discussed.
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