Influence of Gate Doping Concentration on the Characteristics of Amorphous InGaZnO Thin-Film Transistors With HfLaO Gate Dielectric

Abstract

Amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with HfLaO as high-k gate dielectric have been fabricated, and p-type silicon wafers with resistivities of 0.001 ~ 0.002, 0.005, 0.02 ~ 0.021 and $5\sim 10\Omega \cdot $ cm are used as their gate electrodes. The carrier mobility of the samples show an increase with increasing gate acceptor concentration, indicating that the TFT performances are affected by the hole concentration in the gate electrode. The HfLaO gate dielectric is highly polarizable and so produces surface-optical phonons, which can scatter the electrons in the IGZO channel to reduce their mobility. Therefore, this work directly demonstrates that the holes in the gate electrode can have a screening effect to suppress this remote phonon scattering of the gate dielectric on the channel carriers, just like the electrons in the metal gate, ITO gate and n-silicon gate of field-effect transistors.