Effects of temperature on surface plasmon resonance in organic thin-film transistor

Pentacene organic thin-film transistors (OTFTs) adopting n-Si gate electrodes with a wide range of doping concentrations (10¹⁵-10²⁰ cm⁻³) are fabricated to study the effects of the quantum-mechanical interaction between gate electrode and gate dielectric on the carrier mobility in the pentacene channel. At room temperature, significant carrier-mobility reduction is observed for the OTFTs with gate doping concentrations of 1.75 × 10¹⁸ and 4.19 × 10¹⁸ cm⁻³ due to enhanced remote phonon scattering resulting from the resonance between the surface plasmons of the gate electrode and the phonons of the HfLaON gate dielectric (from Hf-O and La-O bonds) and the silicate interlayer (from Si-O bond), respectively, namely the anti-screening effect (ASE). This ASE can be further supported by increasing the measurement temperature from room temperature to 40, 60, and 80 °C, under which the frequency of gate-electrode plasmon increases (due to higher electron thermal energy and also higher electron concentration produced by stronger ionization of dopants in the gate electrode) to enhance, weaken, or create the resonance, resulting in stronger ASE, reduced ASE, or ASE with another phonon mode in the gate dielectric, respectively, in the OTFT. These results can help address the issue of the temperature-dependent reliability of OTFTs operating under heating or at low temperatures.