Illumination-enhanced hysteresis of transistors based on carbon nanotube networks

The hysteresis in single-walled carbon nanotube (SWNT) transistors comprising Si backgate (SiO ₂ on doped Si) is normally attributed to either carrier injections from SWNTs to their surroundings or the presence of charge traps at a Si-SiO ₂ interface. We show that the hysteresis in SWNT transistors with a nearly trap-free Si backgate is thermally activated (activation energy Ea ̃ 129-184 meV) in a dark ambient condition, and it is attributed to hole trappings at the SiO ₂surfaces proximate to SWNTs. Photon-illumination on the SWNT transistor devices with thin SiO ₂ dielectrics (80 nm) results in the ON-current increase due to the effective gating from the photovoltage generated at the Si-SiO ₂ interface. The light-induced simultaneous enhancement of ON-current and hysteresis suggests that the illumination-enhanced hysteresis is due to the photovoltageactivated hole trapping process on SiO ₂ surfaces.