Antenna-Coupled Quantum Well Infrared Photodetectors: Enhancement and Beam-FormingPublic Deposited
This thesis reports on the use of optical antennas, and more broadly, metal optics for the engineered collection and enhancement of infrared photodetectors. These ideas would be useful in enhancing at other wavelengths and other types of detectors, but this work is specifically focused on the Quantum Well Infrared Photodetector (QWIP) and addressing its shortcomings, while enhancing its advantages. Metallic antennas can be used to collect light, resonate, enhance in a nearfield, change polarization, and re-direct the direction of incident light. These properties can be directly applied to QWIP to enhance absorption, apply electric field across the quantum wells (necessary for absorption), and reduce noise by allowing for a smaller electrical volume, and thus a smaller dark current. This project was also interested in extending QWIP and infrared detectors beyond their typical direct collection and enhancement; delocalization of a collector and source can open doors for interesting research and applications. Inspired by microstrip antennas and waveguides typically seen in the microwave, and enabled by a metal-to-metal substrate bonding process, micro-scale patch antennas and waveguides are fabricated to support infrared modes and direct collected light to QWIP. In this work a flexible, modular platform for integration of antennas with QWIP has been developed and demonstrated; a simple metal-to-metal substrate bonding process was integrated with etched QWIP and antennas for a three-dimensional device that is compatible with other semiconductor processes. This process was proven to work with QWIP with the demonstration of an etched Grating Device with a responsivity of 0.12A/V, an improvement over the only other reported small-volume QWIP. The flexibility of this platform was also demonstrated by the addition of BCB microstrip waveguides and antennas. We showed that with a stationary biased absorber, one can waveguide-couple an antenna allowing for delocalized coupling to QWIP. Due to the modular nature of this design and relative simplicity of fabrication, any of these components can be replaced or expanded on allowing either 1) the introduction of QWIP to applications beyond typical focal plane arrays or 2) the use of an emitter instead of absorber for a controlled, directional radiation of infrared.