About My Research

Interests: Photonics and high speed electronic devices and device physics, including lasers, transistors, modulators, detectors, and bio-electronic interfaces.

Silicon Photonics and Heteroepitaxy

• Heterogeneous integration: A project I initiated led to the discovery of techniques for growing defect-free Ge on Si using novel gas precursors. This enables both GaAs-based optoelectronics and III-V CMOS on silicon. The Ge was nearly strain-neutral at typical device temperatures, providing improved reliability for high power devices.
• I developed a device process flow for GeSn photodetectors and modulators in the mid-IR, making silicon photonics a realistic possibility for future optoelectronics.
• Silicon photonics: Silicon is notoriously unreactive with light, and the other Group IV elements (Ge, Sn, C) are hardly better. My research has opened several avenues which are likely to produce efficient Group IV photodetectors, solar cells, and even lasers. Stay tuned!

III-V MOSFETs

• As a postdoc at U.C. Santa Barbara, I am currently leading the growth and fabrication teams which have made the first scalable III-V MOSFETs, using self-aligned techniques. These are the first III-V FETs which can be scaled to nanometer dimensions (20-50nm), to extend Moore's Law for several generations beyond silicon. This work is a delightful collaboration among multiple groups and different universities, ranging from atomic theory to circuits and from California to Massachusetts. At UCSB (as at Stanford), the boundaries between departments are fuzzy, leading to some of the most exciting research collaborations, with different viewpoints available to tackle any problem, and interesting new challenges every day.
• Self-aligned, low resistance contacts: Molecular beam epitaxy (MBE) is a line-of-sight deposition technique, but my work has been able to fill in recesses under the edges of the gate in a MOSFET. We have also produced the lowest contact resistances to InGaAs to date. Low resistance is vital for THz electronics.

Lasers for Metro Area Networks and Fiber-to-the-Home

• 1540nm VCSELs: The first electrically-pumped, dilute nitride VCSELs in the telecommunication band near 1550 nm, for inexpensive, high speed fiber communications. (See reprints at left.) My PhD thesis (5.9 MB) and orals abstract are available too.