Illumination-Enhanced Hysteresis of Transistors Based on Carbon Nanotube Networks

The hysteresis in single-walled carbon nanotube (SWNT) transistors comprising Si backgate (SiO2 on doped Si) is normally attributed to either carrier injections from SWNTs to their surroundings or the presence of charge traps at a Si−SiO2 interface. We show that the hysteresis in SWNT transistors with a nearly trap-free Si backgate is thermally activated (activation energy E a ∼ 129−184 meV) in a dark ambient condition, and it is attributed to hole trappings at the SiO2 surfaces proximate to SWNTs. Photon-illumination on the SWNT transistor devices with thin SiO2 dielectrics (80 nm) results in the ON-current increase due to the effective gating from the photovoltage generated at the Si−SiO2 interface. The light-induced simultaneous enhancement of ON-current and hysteresis suggests that the illumination-enhanced hysteresis is due to the photovoltage-activated hole trapping process on SiO2 surfaces.