Conventional approach to controlling and modulating carrier transport in transistor is by utilizing external electric field. In a typical setting, metal or heavily doped silicon gate is separated by dielectric materials from the active region of semiconductor, forming a metal-insulator semiconductor structure. However, such approach requires physical metal interconnections to the device for electrical modulation, which are constructed up to at least 10 interconnection layers in the state-of-the-art complementary metal-oxide-semiconductor (CMOS) technology. As the technology advances, these interconnections become more and more complicated, and significantly burden the operation of the transistor due to increased parasitic components of the circuit (i.e. parasitic resistance/capacitance).
In order to address such challenges, researchers at the University of California, Berkeley have developed optical interface capable of wireless modulation of electrical current, instead of complicated physical metal interconnects. In particular, they have developed a interface to demonstrate the free-space optical modulation of current. The new capability of optical modulation allows a new class of transistor optical transistor - with unprecedented performance and tunability.
Furthermore, The two critical applications of the new transistor - multi functional logic gates, and ultra-sensitive electrical detection of biomolecules – enable completely new possibilities for multifunctional electronics and ultra-sensitive detection of chemical and bio- molecules. The uniqueness of wavelength-specific modulation of nanophotonic transistors lead to the creation of multi-functional nanophotonic logic gates and circuits where different component generate multiple functionalities in a same circuit layout. In addition, local field enhancement provides a unique opportunity to substantially improve sensitivity of field-effect transistor (FET) based biosensors.