• Krishnamurthi, Mahesh
• Gopalan, Venkatraman
• Badding, John
• Sazio, Pier-John
• He, Rongrui

Abstract

Here we present a novel group of flexible semiconductor electronic/optoelectronic devices made in microstructured optical fibers with extreme aspect ratios. These devices are motivated by incorporating the optoelectronic capabilities of semiconductor structures into optical fibers, the backbone for the modern optical communications. The joint of these two key techniques could enable all-fiber networks, in which light generation, modulation, transmission, and detection can all be performed within a fiber. One very important merit that makes optical fibers so practical in long distance communications is that they are very strong and flexible. The semiconductor materials and structures are thereby required to have comparable strengths and flexibilities, if constructed inside the fibers to realize unprecedented optoelectronics functions. Microstructured optical fibers have a complex two dimensional structure of air holes running down the length. We have demonstrated infiltration of a variety of semiconductor materials into the holes via the unique high pressure chemical vapor deposition. In this presentation, we first report the control of the carrier type and concentration in Si and Ge. Based on this control, we are able to make different types of field effect transistors and realize Si/Ge pn junctions in a fiber for the first time. This should be of considerable significance since pn junctions are the basic building blocks for optoelectronics. For example, our preliminary results show that Si/Ge heterojunctions work as in-fiber photodetectors for the 1.55 µm communication light. In the presentation, we will particularly address the flexibility of these in-fiber devices. These devices are wires or tubes with diameters ranging from 0.5 to 10 µm and lengths up to several tens of centimeters. Although being of polycrystalline nature, they show remarkable flexibilities, for example, they can generally stand > 1% strain without breaking. Generally, single crystalline whiskers and nanowires have proven to have strengths close to the theoretical values. The study of the mechanical behavior of these fine grained semiconductor materials should be highly worthwhile; they may expand the material choice for the flexible electronics and optoelectronics.

Topics

• impedance spectroscopy
• semiconductor
• strength
• wire
• chemical vapor deposition