Evelyn Hu *
Exploring new possibilities of optical and electronic behavior within materials that have been carefully sculpted, modulated and modified at the nanoscale. Creating low-damage and selective processes to provide highest quality & performance structures. Utilizing a semiconductor base platform, but also developing means of heterogeneous materials integration, including the use of bio-templating. Probing and pushing the performance of photonic and electronic structures.
My research explores the new possibilities of optical and electronic behavior within materials that have been carefully sculpted, modulated and modified at the nanoscale. Primarily starting with a semiconductor platform, careful control and understanding of interfaces can give rise to dramatically different materials and device opportunities, such as in wafer-bonded structures, or in semiconductor-superconductor structures. High resolution fabrication processes, such as e-beam lithography and gas-phase etching can create a top-down modulation of optical or electronic properties with dramatic consequences. Such processes need to incorporate and leverage detailed understanding of the material to achieve the best outcomes. This has guided our work on low-damage etch processes and selective photo-electrochemical etching of GaN-based materials. The combined palette of heterogeneous materials and fabrication tools at the nanoscale offer the opportunity to highlight photonic and electronic performance and create devices of enhanced efficiency, speed and performance. At the moment, our group in particular focuses on:
Modulation of the material structure at the nanoscale can dramatically alter and control the nature of the light-matter interactions. In particular, we are investigating photonic crystal structures formed from a wide range of materials, including GaAs, GaN, InP and diamond.
Gallium nitride and its alloys are relatively 'young' materials that have enormous potential for electronic devices, and a host of optical devices that span the wavelength range from visible into the UV. As a 'young' material family, GaN offers enormous challenges and opportunities to develop innovative fabrication strategies that will help to form these materials into the most advantageous device structures that will fully capitalize on their prodigious intrinsic properties. Some of the capabilities we have developed allow the formation of microcavity Light Emitting Diodes, as well as nanophotonic GaN devices.
These days, no palette of fabrication approaches is complete without the inclusion of techniques that are 'borrowed' from Nature. 'Natural' biological fabrication allows precise structural assembly from the nanometer scale to the macroscopic level. There is often a hierarchal organization from one scale to another which is lacking in many synthetic materials and structures. Proceeding to the next step in truly 'heterogeneous integration' of materials and fabrication approaches, our lab is developing materials assembly techniques that use biological templates such as filamentous viruses. The next steps would be to incorporate not only biological templates, but to better understand and utilize biological mechanisms of photon and carrier collection, detection, sensing and switching.