Investigation on Hump Mechanism in Amorphous SiZnSnO Thin-Film Transistor Depending on Si Concentration

Abstract

For the amorphous Si-Zn-Sn-O (a-SZTO) thin-film transistor (TFT), Si can suppress oxygen vacancies, mainly due to higher bonding strength with O compared with Zn or Sn in amorphous oxide ZnSnO semiconductors. When these devices are driven at a low power, a nonideal transfer characteristic of hump phenomenon is observed. As Si concentration increases, this phenomenon is also found even at high voltage. The Si doping changes not only the electrical performance but also the bandgap state. As the Si concentration increases, the conduction band (E-c) raises up to vacuum level. In general, when metal and semiconductor are contacted, a band bending phenomenon occurs at a contact interface due to different work function. This change inE(c)caused by the bandgap change due to Si doping also affects the band bending that can form different barriers at the interface between the metal and the channel. When low drain-to-source voltage (V-ds) is induced, band bending can act as a barrier and cause a hump. So, the hump phenomenon is carefully observed if lowV(ds)is applied to TFT. To make a low-power device, the work function difference between metal and semiconductor must be considered.