Impact of Gate-Electrode Material on Channel-Carrier Mobility of Thin-Film Transistor With High-k Gate Dielectric

Semiconductors (n-Si, n-Ge, n-GaAs, ITO) with various electron concentrations and metals (Au, Al) are applied as gate electrodes of p-channel pentacene organic thin-film transistors (OTFTs) with HfLaON as high-k gate dielectric. On the one hand, for each gate material, the channel-carrier mobility of the sample increases with the gate electron concentration due to the enhanced screening effect of the gate electrode on the remote phonon scattering (RPS) of the gate dielectric. On the other hand, for a gate electron concentration of
$\sim ~{5}\times {10}^{{17}}/{\mathrm {cm}}^{-{3}}$
, the channel-carrier mobility of the n-GaAs-gate device is higher than those of its n-Ge-gate and n-Si-gate counterparts, implying that gate electrode with lower effective electron mass leads to higher channel-carrier mobility. In summary, materials with low effective carrier mass (e.g. n-GaAs) and high carrier concentration (e.g. Al) have high potential as the gate-electrode material to provide stronger gate screening effect on the RPS and so achieve higher channel-carrier mobility.