Dissertation Talk: Expanding the Scalability and Applications of III-V Optoelectronic Devices by Evolution of Thin-Film Vapor-Liquid-Solid Growth

Presentation: Dissertation Talk: EE | December 4 | 2-3 p.m. | 531 Cory Hall

 Mark Hettick

 Electrical Engineering and Computer Sciences (EECS)

Semiconductor materials are a constant limitation and avenue of improvement for the performance and efficiency of electronic and optoelectronic devices. Nowhere is this clearer than in the parallel fields of microelectronics and photovoltaics, where scaling and optimization of silicon-based systems has dominated tangible innovation in their respective markets for decades. While III-V materials have made inroads in both high efficiency photovoltaics and hybrid opto-electronic circuits, they are traditionally limited in terms of scalability and cost due to the expense of lattice-matched substrates for epitaxy.

However, in recent years, the thin-film vapor-liquid-solid (TF-VLS) growth method has been developed to allow scalable III-V growth on non-epitaxial substrates, eliminating this practical barrier. In this talk, I explore and expand the use of two variants to this method to enable new applications in photovoltaics and optoelectronics. First, large-area TF-VLS growth is utilized to explore InP photocathodes on metal substrates with a protective electron selective contact, and direct fuel generation from sunlight is demonstrated with this structure. Second, the templated variant of the TF-VLS method (TLP growth) is discussed, where locally defined crystals can be grown directly on amorphous substrates. Devised initially to expand the scalability of microscale optoelectronics, the TLP method is expanded here by use of a simple thermal growth technique with significantly lower thermal budget. Growth behavior at temperatures compatible with silicon CMOS, glass, and plastics is explored, and proof-of-concept light emitting and transistor devices are demonstrated.

Advisor: Ali Javey

 mark.hettick@berkeley.edu