| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 100 === In a recent development, tin (Sn)-based group-IV semiconductor compounds has attracted research attention for new electronic and photonic devices. The incorporation of Sn modulates the bandgap of the host IV-IV compounds, and, above a certain Sn composition, the energy band of the IV-IV compounds changes from an indirect to a direct band gap. Here, we investigate a series of Ge1-xSnx alloy with various Sn compositions up to 14% and 17% grown on Ge and Si wafer respectively using low-temperature Molecular Beam Epitaxy. To characterize band structure and optical properties of these GeSn samples, we performed spectroscopic Fourier Transform Infra-Red (FTIR), ellipsometer, and photoluminescence (PL) measurements. The Γ-to-Γ optical energy gap of Ge1-xSnx alloys can be determined by FTIR. Several critical point features, corresponding to E1, E1+Δ1, and E0’ transitions, are observed in ε1 and ε2. The
positions of E1 and E1+Δ1 shift toward to lower energy as Sn composition increases.
Furthermore, the optoelectronic and electronic devices can be designed for applications by those analyzed.
We propose a new design of Sn-based group-IV structure for resonant tunneling diode (RTD). The proposed RTD is composed of direct-bandgap Ge1-xSnx/SiyGezSn1-y-z quantum well which can be directly grown on Si. By optimizing the composition and strain in the quantum well, a high peak-to-valley ratio of 7.69 is obtained. Those results suggest our proposed RTD design can be integrated into CMOS circuits for useful applications.
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