Department of Physics
Condensed Matter Seminar

Discovery and development of novel nanostructures have opened up opportunities for technological applications and fundamental studies. Controlled modulation of the composition of nanoscale structures during synthesis offers a means for encoding information or function that is independent of conventional lithography methods. We describe controlled synthesis of modulation-doped silicon nanowires in which key properties, including the size, period and number of differentially doped regions, are defined during growth. These new nanoscale building blocks open up exciting opportunities is several areas. First, an approach for lithography-free addressing based on modulation doped silicon nanowire field-effect transistor arrays has been developed, and the assembly and demonstration of address decoder circuits will be discussed. Second, modulation doping has been used to create controllable barriers within nanowires, which provides a general bottom-up approach to form quantum structures with well-defined size. Single quantum dots as well as coupled quantum dots with controllable inter-dot coupling will be discussed. Third, spatial photocurrent measurements made on p-i-n modulation doped nanowires exhibit large amplification in the intrinsic region due to an avalanche mechanism. Studies of the impact ionization coefficients of electrons and holes in silicon nanowires will also be discussed. These results demonstrate the great potential of modulated silicon nanowires building blocks for both nanoelectronics and nanophotonics.