Numerical Analysis on Effective Mass and Traps Density Dependence of Electrical Characteristics of a-IGZO Thin-Film Transistors

• Main Authors: Jihwan Park, Do-Kyung Kim, Jun-Ik Park, In Man Kang, Jaewon Jang, Hyeok Kim, Philippe Lang, Jin-Hyuk Bae
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Electronics
• Subjects: a-igzo thin-film transistors; effective mass; numerical simulation; electrical characteristics; scattering
• Online Access: https://www.mdpi.com/2079-9292/9/1/119

We have investigated the effect of electron effective mass (<i>m</i>_e*) and tail acceptor-like edge traps density (<i>N</i>_TA) on the electrical characteristics of amorphous-InGaZnO (a-IGZO) thin-film transistors (TFTs) through numerical simulation. To examine the credibility of our simulation, we found that by adjusting <i>m</i>_e* to 0.34 of the free electron mass (m_o), we can preferentially derive the experimentally obtained electrical properties of conventional a-IGZO TFTs through our simulation. Our initial simulation considered the effect of <i>m</i>_e* on the electrical characteristics independent of <i>N</i>_TA. We varied the <i>m</i>_e* value while not changing the other variables related to traps density not dependent on it. As <i>m</i>_e* was incremented to 0.44 m_o, the field-effect mobility (<i>&#181;</i>_fe) and the on-state current (<i>I</i>_on) decreased due to the higher sub-gap scattering based on electron capture behavior. However, the threshold voltage (<i>V</i>_th) was not significantly changed due to fixed effective acceptor-like traps (<i>N</i>_TA). In reality, since the magnitude of <i>N</i>_TA was affected by the magnitude of <i>m</i>_e*, we controlled <i>m</i>_e* together with <i>N</i>_TA value as a secondary simulation. As the magnitude of both <i>m</i>_e* and <i>N</i>_TA increased, <i>&#181;</i>_fe and Ion deceased showing the same phenomena as the first simulation. The magnitude of <i>V</i>_th was higher when compared to the first simulation due to the lower conductivity in the channel. In this regard, our simulation methods showed that controlling <i>m</i>_e* and <i>N</i>_TA simultaneously would be expected to predict and optimize the electrical characteristics of a-IGZO TFTs more precisely.