Thermal Infrared Detection Using Antenna-Coupled Metal-Oxide-Metal Diodes

This project focuses upon devices that can be used for detection of thermal or long-wave infrared radiation, which is a frequency range for which developing detectors is of special interest. Objects near 300 K, such as humans and animals, emit radiation most strongly in this range, and absorption is relatively low in the LWIR atmospheric window between 8 and 14 μm. These facts provide motivation to develop detectors for use in this frequency range, which could be used for target detection, tracking, and navigation in autonomous vehicles. The devices discussed in this dissertation, referred to as dipole antenna-coupled metal-oxide-metal diodes (ACMOMDs), feature a half-wavelength antenna that couples electromagnetic radiation to a metal-oxide-metal diode, which acts as a nonlinear junction to rectify the signal. These detectors are patterned using electron beam lithography and fabricated with shadow evaporation metal deposition.

Along with offering CMOS compatible fabrication, these detectors provide high speed and frequency selective detection without biasing, a small pixel footprint, and full functionality at room temperature without cooling. The detection characteristics can be tailored to provide for multi-spectral imaging in specific applications by modifying device geometries.

In this dissertation, a brief introduction to currently available infrared detectors is given, thereby providing a motivation for why ACMOMDs were chosen for this project. An overview of the metal-oxide metal diode is provided, detailing principles of operation and detection. The fabrication of ACMOMDs is described in detail, from bonding pad through device processes. Direct-current current-voltage characteristics of symmetrical and asymmetrical antenna diodes are presented. An experimental infrared test bench used for determining the detection characteristics of these detectors is detailed, along with the figures of merit which have been measured and calculated. The measured performance of fabricated ACMOMDs is presented, including responsivity, noise performance, signal-to-noise ratio, noise-equivalent power, and normalized detectivity. The response as a function of infrared input power, polarization dependence, and antenna-length dependence of these devices is also presented.