Highlight

  • Detailed analysis of the electrical performance enhancements achieved with Ni S/D electrodes, including higher field-effect mobility (µFE), steeper sub-threshold slope (SS), and improved gate induced drain leakage(GIDL).
  • Investigation into the bias stability under positive and negative bias stress tests, demonstrating the superior stability of a-ITZO FETs with Ni S/D electrodes.
  • Elucidation of the defect control mechanism associated with S/D electrode materials, particularly the role of Ni electrodes in reducing oxygen vacancies (Vo) and improving electrical properties and bias stability.

Schematic image to describe the effects of S/D metals on oxygen vacancy diffusion in the AOS FETs

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Abstract

The gate-bias stability of amorphous indium-tin-zinc-oxide (a-ITZO) field-effect transistors (FETs) is critical for their display and emerging memory applications. However, a-ITZO FETs suffer from insufficient gate-bias stability induced by oxygen vacancies in the channel layer. To address this issue, we examined the impact of source/drain (S/D) electrode materials (W, Mo, and Ni) on the oxygen vacancy formation and electrical characteristics in the a-ITZO FETs. Through X-ray photoelectron spectroscopy (XPS) analysis, we found that the Ni S/D electrode is effective in forming fewer oxygen vacancies in the a-ITZO channel, whereas W and Mo induce many oxygen vacancies. Our proposed model suggests that the Ni electrode absorbing less oxygen from the a-ITZO films compared to other electrodes leads to fewer oxygen vacancies in the a-ITZO channel. Notably, the a-ITZO FETs incorporating Ni S/D electrodes exhibit not only excellent electrical performance, including a high field-effect mobility of 27.6 cm2 /Vs, a steep subthreshold swing (SS) of 71.8 mV/decade, and high on/off ratio of ∼ 107 , but also an outstanding gate-bias stability ( ΔVth = − 0.04 V) under negative bias stress (NBS) testing. These findings underscore the potential of Ni S/D electrodes in advancing the development of high-performance, stable a-ITZO FETs for the next-generation semiconductor devices. [Link to Journal, IEEE Transactions on Electron Devices]

Congratulations, Seong Ui!