Research
Mid-infrared (mid-IR) lasers
Compact, high-efficiency, mid-IR laser sources in the ~3-5 µm range are exciting for a number of applications including industrial gas monitoring, chemical/bio sensors, IR countermeasures, and communications systems. Current approaches to compact mid-IR sources include type-II “W” structures, quantum cascade lasers (QCLs), and type-I quantum wells on GaSb. Type-I GaInAsSb/AlGaAsSb active regions grown on GaSb offer significant advantages over other approaches, including room temperature operation, low threshold current density, high output power, and temperature stable operation. Specifically, they feature more straightforward device design and growth than QCLs and substantially higher gain and operating temperatures than W structures.
Metal/semiconductor nanocomposites for terahertz (THz) generation
There is currently a great need for systems to detect and identify chemical and biological agents. The 0.3-3 THz frequency range is a critical regime for such applications because of the many vibrational and rotational lines of key chemical/biological agents. The needs of such systems: high sensitivity/specificity, compact, rugged, portable, and power efficient place significant demands upon the THz sources. They must operate at room temperature and be widely tunable with narrow linewidth and high output power, electrically-driven, power-efficient, compact/rugged, and (preferably) operate cw. This requires sources that are far superior to those currently available. We are investigating new epitaxial metal/semiconductor nanocomposites to dramatically increase the performance of photomixer THz sources.
(Practical) silicon-based lasers
It has long been recognized that the integration of silicon-based electronics with photonics could be extremely powerful. This field has blossomed in recent years with the realization that on-chip interconnects are fast becoming a substantial source of power dissipation and delay. This coincides with historical progression of light as the preferred data transmitting medium on progressively smaller and smaller length scales: from ocean-to-ocean, city-to-city, ..., board-to-board, chip-to-chip, and eventually on-chip. Virtually all of the necessary optical components are in place for silicon-based optoelectronics, with the key exception being a monolithic, electrically-pumped, CMOS-compatible laser. The ultimate length scales and applications that optics will penetrate will depend on whether the silicon-laser problem can be solved, as well as its ultimate performance.
III-V transistors on silicon
The ITRS roadmap predicts serious difficulties in the coming years with simply scaling silicon CMOS. As a result, the silicon MOSFET is being virtually reinvented; high-k dielectrics are replacing SiO2 as the preferred oxide in MOSFETs. As a result, the arguments for a Si or SiGe channel become far less compelling. We are collaborating with Professors Sanjay Banerjee and Jack Lee to develop high-performance III-V MOSFETs.