A threshold voltage and drain current model for symmetric dual-gate amorphous InGaZnO thin film transistors

  • Minxi Cai
  • Ruohe YaoEmail author
Research Paper


Based on the drift-diffusion theory, a simple threshold voltage and drain current model for symmetric dual-gate (DG) amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) is developed. In the subthreshold region, most of the free electrons are captured by trap states in the bandgap of a-IGZO, thus the ionized trap states are the main contributor to the diffusion component of device drain current. Whereas in the above-threshold region, most of the trap states are ionized, and free electrons increase dramatically with gate voltage, which in turn become the main source of the drift component of device drain current. Therefore, threshold voltage of DG a-IGZO TFTs is defined as the gate voltage where the diffusion component of drain current equals the drift one, which can be determined with physical parameters of a-IGZO. The developed threshold voltage model is proved to be consistent with trap-limited conduction mechanism prevailing in a-IGZO, with the effect of drain bias being also taken into account. The gate overdrive voltage-dependent mobility is well modeled by the derived threshold voltage, and comparisons of the obtained drain current with experiment data show good verification of our model.


amorphous InGaZnO drift-diffusion current dual-gate thin film transistors threshold voltage 



This work was supported by National Natural Science Foundation of China (Grant No. 61274085) and Science and Technology Research Projects of Guangdong Province (Grant No. 2015B090909001).


  1. 1.
    Nomura K, Ohta H, Takagi A, et al. Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors. Nature, 2004, 432: 488–492CrossRefGoogle Scholar
  2. 2.
    Kamiya T, Nomura K, Hosono H. Present status of amorphous In-Ga-Zn-O thin-film transistors. Sci Tech Adv Mater, 2010, 11: 044305CrossRefGoogle Scholar
  3. 3.
    Lee C T, Huang Y Y, Tsai C C, et al. A novel highly transparent 6-in. AMOLED display consisting of IGZO TFTs. SID Symp Dig Tech Papers, 2015, 46: 872–875CrossRefGoogle Scholar
  4. 4.
    Yeom H I, Moon G, Nam Y, et al. Oxide vertical TFTs for the application to the ultra high resolution display. SID Symp Dig Tech Paper, 2016, 47: 820–822CrossRefGoogle Scholar
  5. 5.
    Yang B D, Oh J M, Kang H J, et al. A transparent logic circuit for RFID tag in a-IGZO TFT technology. Etri J, 2013, 35: 610–616CrossRefGoogle Scholar
  6. 6.
    Shabanpour R, Ishida K, Perumal C, et al. A 2.62 MHz 762 μW cascode amplifier in flexible a-IGZO thin-film technology for textile and wearable-electronics applications. In: Proceedings of International Semiconductor Conference Dresden-Grenoble (ISCDG), Dresden, 2013. 1–4Google Scholar
  7. 7.
    Kim Y, Kim S, Kim W, et al. Amorphous InGaZnO thin-film transistor—part II: modeling and simulation of negative bias illumination stress-induced instability. IEEE Trans Electron Dev, 2012, 59: 2699–2706CrossRefGoogle Scholar
  8. 8.
    Migliorato P, Chowdhury M D H, Um J G, et al. Light/negative bias stress instabilities in indium gallium zinc oxide thin film transistors explained by creation of a double donor. Appl Phys Lett, 2012, 101: 123502CrossRefGoogle Scholar
  9. 9.
    Song J H, Oh N, Anh B D, et al. Dynamics of threshold voltage instability in IGZO TFTs: impact of high pressurized oxygen treatment on the activation energy barrier. IEEE Trans Electron Dev, 2016, 63: 1054–1058CrossRefGoogle Scholar
  10. 10.
    He X, Wang L, Deng W, et al. Improved electrical stability of double-gate a-IGZO TFTs. SID Symp Dig Tech Paper, 2015, 46: 1151–1154CrossRefGoogle Scholar
  11. 11.
    Hong S, Lee S, Mativenga M, et al. Reduction of negative bias and light instability of a-IGZO TFTs by dual-gate driving. IEEE Electron Device Lett, 2014, 35: 93–95CrossRefGoogle Scholar
  12. 12.
    Cheng K G, Khakifirooz A. Fully depleted SOI (FDSOI) technology. Sci China Inf Sci, 2016, 59: 061402CrossRefGoogle Scholar
  13. 13.
    Baek G, Abe K, Kuo A, et al. Electrical properties and stability of dual-gate coplanar homojunction DC sputtered amorphous indium-gallium-zinc-oxide thin-film transistors and its application to AM-OLEDs. IEEE Trans Electron Dev, 2011, 58: 4344–4353CrossRefGoogle Scholar
  14. 14.
    Abe K, Takahashi K, Sato A, et al. Amorphous In-Ga-Zn-O dual-gate TFTs: Current-voltage characteristics and electrical stress instabilities. IEEE Trans Electron Dev, 2012, 59: 1928–1935CrossRefGoogle Scholar
  15. 15.
    Baek G, Kanicki J. Modeling of current-voltage characteristics for double-gate a-IGZO TFTs and its application to AMLCDs. J Soc Inf Display, 2012, 20: 237–244CrossRefGoogle Scholar
  16. 16.
    Son K S, Jung J S, Lee K H, et al. Characteristics of double-gate Ga-In-Zn-O thin-film transistor. IEEE Electron Dev Lett, 2010, 31: 219–221CrossRefGoogle Scholar
  17. 17.
    Lee S, Ghaffarzadeh K, Nathan A, et al. Trap-limited and percolation conduction mechanisms in amorphous oxide semiconductor thin film transistors. Appl Phys Lett, 2011, 98: 203508CrossRefGoogle Scholar
  18. 18.
    Lee S, Nathan A, Robertson J, et al. Temperature dependent electron transport in amorphous oxide semiconductor thin film transistors. In: Proceedings of IEEE International Electron Devices Meeting (IEDM), Washington, 2011. 1–4Google Scholar
  19. 19.
    Li L, Lu N, Liu M. Field effect mobility model in oxide semiconductor thin film transistors with arbitrary energy distribution of traps. IEEE Electron Dev Lett, 2014, 35: 226–228CrossRefGoogle Scholar
  20. 20.
    Lee S, Yang Y, Nathan A. Modeling current-voltage behaviour in oxide TFTs combining trap-limited conduction with percolation. SID Symp Dig Tech Paper, 2013, 44: 22–25CrossRefGoogle Scholar
  21. 21.
    Kamiya T, Nomura K, Hosono H. Electronic structures above mobility edges in crystalline and amorphous In-Ga-Zn-O: percolation conduction examined by analytical model. J Display Tech, 2009, 5: 462–467CrossRefGoogle Scholar
  22. 22.
    Qiang L, Yao R H. A new definition of the threshold voltage for amorphous InGaZnO thin-film transistors. IEEE Trans Electron Dev, 2014, 61: 2394–2397CrossRefGoogle Scholar
  23. 23.
    Zhong C, Lin H, Liu K, et al. Improving electrical performances of p-type SnO thin-film transistors using double-gated structure. IEEE Electron Dev Lett, 2015, 36: 1053–1055CrossRefGoogle Scholar
  24. 24.
    Bae M, Kim Y, Kong D, et al. Analytical models for drain current and gate capacitance in amorphous InGaZnO thin-film transistors with effective carrier density. IEEE Electron Dev Lett, 2011, 32: 1546–1548CrossRefGoogle Scholar
  25. 25.
    Kim Y, Bae M, Kim W, et al. Amorphous InGaZnO thin-film transistors—Part I: Complete extraction of density of states over the full subband-gap energy range. IEEE Trans Electron Dev, 2012, 59: 2689–2698CrossRefGoogle Scholar
  26. 26.
    Ghittorelli M, Torricelli F, Colalongo L, et al. Accurate analytical physical modeling of amorphous InGaZnO thin-film transistors accounting for trapped and free charges. IEEE Trans Electron Dev, 2014, 61: 4105–4112CrossRefGoogle Scholar
  27. 27.
    Shih C H, Wang J S. Analytical drift-current threshold voltage model of long-channel double-gate MOSFETs. Semicond Sci Tech, 2009, 24: 105012CrossRefGoogle Scholar
  28. 28.
    Corless R M, Gonnet G H, Hare D E G, et al. On the Lambert W function. Adv Comput Math, 1996, 5: 329–359MathSciNetCrossRefzbMATHGoogle Scholar
  29. 29.
    Huang J, Deng W, Zheng X, et al. A compact model for undoped symmetric double-gate polysilicon thin-film transistors. IEEE Trans Electron Dev, 2010, 57: 2607–2615CrossRefGoogle Scholar
  30. 30.
    Sze S M, Ng K K. Physics of Semiconductor Devices. 3rd ed. Hoboken: John Wiley & Sons, Inc., 2006. 303–314CrossRefGoogle Scholar
  31. 31.
    Bhoolokam A, Nag M, Steudel S, et al. Conduction mechanism in amorphous InGaZnO thin film transistors. Jpn J Appl Phys, 2016, 55: 014301CrossRefGoogle Scholar
  32. 32.
    Tsuji H, Nakata M, Sato H, et al. Efficient simulation model for amorphous In-Ga-Zn-O thin-film transistors. J Display Tech, 2014, 10: 101–106CrossRefGoogle Scholar
  33. 33.
    Tsormpatzoglou A, Hastas N A, Choi N, et al. Analytical surface-potential-based drain current model for amorphous InGaZnO thin film transistors. J Appl Phys, 2013, 114: 184502CrossRefGoogle Scholar
  34. 34.
    Zong Z, Li L, Jin J, et al. Analytical surface-potential compact model for amorphous-IGZO thin-film transistors. J Appl Phys, 2015, 117: 215705CrossRefGoogle Scholar
  35. 35.
    Vissenberg M C J M, Matters M. Theory of the field-effect mobility in amorphous organic transistors. Phys Rev B, 1998, 57: 12964–12967CrossRefGoogle Scholar
  36. 36.
    Li L, Lu N, Liu M, et al. General Einstein relation model in disordered organic semiconductors under quasi-equilibrium. Phys Rev B, 2013, 90: 214107CrossRefGoogle Scholar
  37. 37.
    Lu N, Li L, Liu M. Universal carrier thermoelectric-transport model based on percolation theory in organic semiconductors. Phys Rev B, 2015, 91: 195205CrossRefGoogle Scholar

Copyright information

© Science China Press and Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  1. 1.School of Electronic and Information EngineeringSouth China University of TechnologyGuangzhouChina

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