Silicon Nanophotonics and Photovoltaics: Materials Scientists’ New Role in the Next Information Age and Alternative Energy Era
Dr. Donghwan Ahn
University of Texas, Austin
Friday, June 05, 2009
3:00 P.M.
LMR 353
One of the most important achievements made by materials scientists in this decade has been the successful exploration of silicon-based group IV materials as a new viable photonic solutions platform – a realm that has been traditionally dominated by III-V compound semiconductors. Materials engineers are currently being urged to develop silicon’s advanced photonic functionalities, and especially, the importance of silicon at the photon-electron conversion interface is utmost in two main application areas: 1) the on-chip optical interconnect and 2) photovoltaics as an alternative energy solution.
The first part of this presentation will address the emerging silicon CMOS-compatible nanophotonic materials and devices for the on-chip optical interconnect applications, such as optical clocking for the microprocessor. Migration from fiber-optic applications to on-chip optical interconnect requires the integration of waveguide and Si-based active photonic devices. The talk will present the world’s first Ge p-i-n photodetector (PD) monolithically integrated with waveguides on Si substrate, which boasts high-efficiency (~ 90 %), high-speed (> 7.5 GHz), and low leakage current. It retained high performance at low voltages, thus satisfying the low-voltage requirement of Si CMOS circuits. Design criteria for evanescent waveguide-detector coupling, as well as the effects of coupling structure design and the fabrication variation on the key coupling criteria will be discussed.
In the second part of presentation, a few important examples of novel research approaches to making solar cells a more economical and viable future energy solution will be introduced. Similarity and compatibility of technologies between optical interconnect devices and photovoltaic devices will be pointed out, and the audience will learn how the materials engineers can effectively contribute in this increasingly important field.