IEEE Journal of the Electron Devices Society (Jan 2019)

Effects of Crystallinity on the Electrical Characteristics of Counter-Doped Polycrystalline Germanium Thin-Film Transistor via Continuous-Wave Laser Crystallization

  • Yi-Shao Li,
  • Chun-Yi Wu,
  • Chan-Yu Liao,
  • Jun-Dao Luo,
  • Kai-Chi Chuang,
  • Wei-Shuo Li,
  • Huang-Chung Cheng

DOI
https://doi.org/10.1109/JEDS.2019.2914831
Journal volume & issue
Vol. 7
pp. 544 – 550

Abstract

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The crystallinity of polycrystalline germanium (poly-Ge) films were demonstrated through continuous-wave laser crystallization (CLC) with Gaussian-distribution beam profile. The different grain sizes of CLC poly-Ge were observed in their three crystallization regions, which were 2 $\mu \text{m}$ , 680 nm, and 90 nm for the central, transition, and edge regions, respectively. Furthermore, the relation between crystallinity and carrier types in these three regions of counter-doped CLC poly-Ge films were investigated. In the central and transition regions, the CLC poly-Ge films with relatively low hole concentration were easily converted to n-type poly-Ge films through a counter-doping process. In contrast, the edge region with poor crystallinity exhibited p-type behavior due to high defect-generated hole concentration. According to these material properties of counter-doped CLC poly-Ge films, the corresponding transfer characteristics of p-channel poly-Ge thin-film transistor for three crystallization regions were further investigated. Subsequently, high-performance p-channel poly-Ge thin-film transistors in the central region exhibited a superior field-effect mobility of 792.2 cm2/V-s.

Keywords