Analysis and design of carbon nanotube based field effect transistors for nano infrared sensors

It has been demonstrated that carbon nanotube field effect transistor (CNTFET) is a promising device to improve the performance of carbon nanotube (CNT) infrared (IR) sensors by modulating the doping level of the CNT channel. However, how to optimize the performance of the CNTFET based IR sensor is not well understood. In particularly, there was limited study on the design of transistor´s gate structure, which determines its energy band profile. In order to improve our understating of its detection mechanism and guide for an optimized design, a multi-gate CNTFET was fabricated, which can control the doping level of the source, drain and nanotube channel independently. Photovoltaic characteristics were observed in bias dependent measurement by varying the intensity of incident IR source. In addition, the polarization dependent measurement was conducted, the detector showed clearly polarization anisotropy, and highest photocurrent was obtained when the polarization is parallel to the nanotube. Its temporal photocurrent responses using different gates were investigated. The results showed that photocurrent had similar photo-responses by applying voltages to the gates at different positions, implying the sensor design can be simplified into a single gate.