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Metallic Nanostructures in Semiconductor Photonic Devices

by Seth Bank
Lab for Advanced Semiconductor Epitaxy (LASE)

Prof. Seth Bank and his research group are investigating new materials to solve long-standing challenges that will potentially enable fundamentally new photonic devices with diverse applications, such as solar power generation, chemical/gas sensing, and optical communications. The integration of metals and semiconductors offers incredible possibilities for new electronic and (nano)photonic devices for these applications, particularly with recent advances in plasmonics and related fields. Unfortunately, metals are typically relegated to the periphery of semiconductor devices, due to materials challenges associated with their integration with semiconductors.

Prof. Bank is working on these challenges in collaboration with Prof. Matthew Gilbert at the University of Illinois Urbana-Champaign to better understand these materials at a fundamental level, using rigorous theory. He is collaborating with Prof. Ed Yu, also a member of the UT ECE faculty, as well as Profs. Xiuling Li and James Coleman at the University of Illinois at Urbana-Champaign on materials characterization and semiconductor device applications.

ErAs and the other semimetallic rare-earth monopnictides provide a potential pathway to integration, as they may be epitaxially embedded as nanoparticles into high-quality III-V semiconductors (e.g. GaAs), with thermodynamically stable interfaces. They have recently demonstrated that these materials can be integrated with semiconductor nanostructures, without degrading the optical properties of the semiconductor. They have also dramatically reduced the resistance of tunnel junctions that are used to connect the junctions of multijunction solar cells, by controlling the morphology of ErAs nanoparticles (e.g. size and shape) placed at the p-n junction. There are several key challenges that remain, however. Tight control of the size distribution and placement of the metallic nanostructures is essential for device applications, but this is impossible with current crystal growth techniques. Additionally, the metal and semiconductor materials do not adhere to one another, complicating how close the optically active semiconductor layers can be to the metallic nanostructures, without degrading the properties of either. Close proximity is essential for taking advantage of near-field optical enhancement effects, such as optical antenna structures.

Solving these challenges requires the exploration of novel methods in order to realize the full potential of metals in semiconductor photonic devices, potentially enabling fundamentally new photonic device functionality with diverse applications such as solar power generation, chemical/gas sensing, and optical communications.

Acknowledgement: This work is supported by the Army Research Office (standard program and PECASE), Air Force Office of Scientific Research (YIP), and the National Science Foundation (CAREER).