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A study on high-performance photodetector based on transition metal dichalcogenides
- Author(s)
- 박영서
- Alternative Author(s)
- Youngseo Park
- Advisor
- 허준석
- Department
- 일반대학원 전자공학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2021-08
- Language
- eng
- Keyword
- broadband detection; photodetector; selective detection; transition metal dichalcogenide; van der Waals heterostructure
- Alternative Abstract
- Two-dimensional layered metal dichalcogenide (TMD), atomically composed of a transition metal and two chalcogen atoms, has attracted great interest in photodetector due to superior characteristics such as adjustable bandgap, strong absorption, and flexibility. Especially, TMD can easily form heterojunction despite lattice mismatch by out-of-plane van der Waals (vdWs) bonding, which opens up the possibility of various energy band alignment. In this thesis, author conducted several studies for high-performance photodetector by using unique characteristics of TMD, which consists of three main topics. First, MoS2 phototransistor was fabricated and analyzed to understand its characteristics. By investigating bias-dependent properties, it is confirmed that responsivity is controlled with bias, and that it is caused by traps. Hence, the interface traps between MoS2 channel and gate oxide were closely investigated by analyzing temperature-dependent properties. Next, the study has been carried out to improve responsivity in MoS2 phototransistor. To this end, author adopts two approaches: cavity effect and additional absorption layer. Al metal gate was adopted in MoS2 phototransistor to confine light across MoS2 channel and gate oxide that serve as cavities. Moreover, absorption peak wavelength is adjusted by the thickness of MoS2 and gate insulator. In a different approach, perovskite was used as additional absorption layer on MoS2. The carriers, photogenerated in the perovskite layer, are transported into the MoS2 channel, which helps the incomplete light absorption in the thin MoS2. Finally, author has studied MoS2/Ge vdWs heterojunction photodetectors to extend the cutoff range. The vdWs force in TMDs enable formation of new heterojunction regardless lattice constant. The MoS2/Ge vdWs heterostructure, composed of large-bandgap MoS2 and small-bandgap Ge, can achieve broadband detection. Moreover, MoS2/Ge photodiode is designed to enable wavelength-selective detection according to the bias. Furthermore, high responsivity and fast response MoS2/Ge vdW heterojunction phototransistor was demonstrated. I believe that these works will be helpful to use photodetectors based on TMDs and understand these properties.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Electronic Engineering > 4. Theses(Ph.D)
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