Meyer–Neldel Rule and Extraction of Density of States in Amorphous Indium–Gallium–Zinc-Oxide Thin-Film Transistor by Considering Surface Band Bending

概要

論文の詳細を見る
In this study, we analyzed the temperature-dependent characteristics of amorphous indium–gallium–zinc-oxide (a-IGZO) thin-film transistors (TFTs). We observed that a-IGZO TFTs obey the Meyer–Neldel rule (MN rule) at low gate-to-source voltage ($V_{\text{GS}}$) and the inverse MN rule at high $V_{\text{GS}}$, both of which can be explained by the statistical shift of Fermi level and electrostatic potential. Large Fermi level movement for small $V_{\text{GS}}$ change and the inverse MN rule, which are hardly observed for conventional amorphous TFTs, indicate that there is a very low density of state (DOS) in the sub-bandgap region for a-IGZO TFTs and the performance of TFTs is not affected by contact characteristics, respectively. By using the field-effect method and considering surface band bending, we extracted the DOS in the sub-bandgap region, the distribution of which is clearly distinguished by deep and tail states. The calculated parameters for tail and deep states were $N_{\text{ta}} = 3.5 \times 10^{17}$ cm-3 eV-1, $E_{\text{ta}} = 0.18$ eV, $N_{\text{da}} = 1.6\times 10^{16}$ cm-3 eV-1, and $\sigma_{\text{da}} = 0.21$ eV.
2010-03-25