| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 95 === The band offset at the heterojunction of Si/epi-Ge/Si quantum well can have the critical influence on device characteristics. The Si-cap can be served as a passivation layer to facilitate further gate dielectrics growth and the possible strained Si channel. Despite of the high carrier mobility of Ge than that of Si, the threshold voltage (Vth) shift of the Ge quantum well pFETs is dependent on the thickness of the Si-cap and the thickness of the Ge quantum well. As the thickness of the Si-cap and the Ge quantum well increase, the subthreshold slpoe (SS) of the Ge quantum well pFETs increases. Due to the hole confinement effect of the Ge quantum well, the drain leakage current of the Ge quantum well pFETs increases significantly.
Solar cells can be fabricated from a lot of different semiconductor materials, but most commonly silicon –single crystal Si, polycrystalline Si, and amorphous Si. The thin film solar cells are based on single crystal Si, which can reduce defects resulting in the increase in efficiency. The single crystalline Ge on glass is fabricated using the wafer bonding and smart cut techniques. A simple solar cell is demonstrated using the Ge-on-glass (GOG) and a metal-oxide-semiconductor (MOS) structure. Simulation results show that the single crystal Si with a thin Ge layer can be combined to increase the efficiency of the thin film solar cells. The device simulation has been carried out by the commercial tool [Synopsys Sentaurus Tcad Simulator]. Results show that a thinner layer of Ge indeed increases the solar cell efficiency.
The metal-oxide-semiconductor (MOS) tunneling diodes were utilized as light emitting diodes based on that the tunneling gate current recombines with accumulated carriers. And this results in radiative recombination. The SiGe heterojunction metal-oxide-semiconductor light-emitting diodes (MOS LED) were reported in chapter 4. Holes on the valence band edge of quantum well recombine with and the electrons on the conduction band edge, and this leads to the radiative luminescence.
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