Infrared sensing systems using carbon nanotube based photodetectors.

摘要

Infrared (IR) sensing systems have versatile applications; however, low performance and high cost of the conventional photodetectors have prevented their widespread utilization in various fields. Carbon nanotube (CNT), a promising nano-material with excellent electrical and optical properties, has potential to develop high performance IR detectors compared to their conventional counterparts. However, there are three major difficulties that impede the application of CNT based photodetectors for imaging systems. Firstly, there are challenges in design, fabrication, and testing of CNT photodetectors because of their nano-scale size and unique geometry. Secondly, the small diameter of the CNTs results in low fill-factor (absorption area). Thirdly, it is difficult to fabricate large scale of photodetector array for high resolution focal plane due to the limitations on the efficiency and cost of the manufacturing. The issues related to the design and fabrication of CNT based photodetectors were addressed by configuring the device in field effect transistors with different metal and gate structures. In addition, the theoretical foundations as well as the implementation schemes for the development of nano-structure lens to improve absorption efficiency of IR detectors were developed. The topics include the optical antennas that confine light into a sub-wavelength volume, as well as photonic crystals to increase the effective absorption area. Furthermore, a novel CNT based IR sensing system was developed. The experimental results showed that the new IR sensing system can achieve the superb performance enabled by CNT based photodetectors, and, at same time, to obtain high resolution and efficient imaging.