Gate Dielectric Scaling Of Top Gate Carbon Nanoribbon On Insulator Transistors

摘要

The effects of gate dielectric constant and thickness on the performance of top gate carbon nanoribbon on insulator transistors are studied using a π-orbital quantum simulation model. The focus is on both the zero Schottky barrier (SB) source-drain contacts and the metal-oxide-semiconductor field effect transistor (MOSFET)-like doped source-drain contacts. The gate dielectric constant has little effect on the on/off current ratio, channel transconductance g_m, and switching performance in SB contact devices. However, the on/off current ratio, the channel transconductance, and the switching performance significantly improve with high-K gate dielectric in doped contact devices. The physics is related to the modulation of the tunnel barrier. In SB contact devices, the on-state current is limited by the SB, and therefore, the improvement in on/off current ratio and transconductance is insignificant. However, the tunnel barrier modulation in the subthreshold regime is similar in both types of contact and the inverse subthreshold slope has similar improvement with high-K gate dielectrics. The unity current gain frequency (f_T=g_m/2πC_g) degrades with high-K gate dielectric in SB contact devices and improves in doped contact devices. This is because the gate capacitance does not change much with dielectric constant and g_m has a significant improvement in doped contact devices. The device performance improves with thinner gate oxide. The on/off current ratio and the inverse subthreshold slope scale as square root of oxide thickness.