Electronic and Photonic Materials

Electronic and Photonic Materials research at Boston University is invested in exciting work in III-V nitrides, carbon nanotubes, fiber optic sensors, quantum dots and computational modeling. Engineering breakthroughs like the blue LED were produced by Boston University labs and interdisciplinary researchers continue to explore myriad applications, such as health care, national defense, information systems and other areas.

Research in this area of involves faculty from various departments within the College of Engineering and College of Arts and Sciences. Scientists in this group share facilities, have collaborative grants, and publish their scientific findings jointly.

Researchers in the electronic and photonics materials thrust address issues related to synthesis, processing and structural and optoelectronic characterization of the families of Nitride semiconductors, silicon based nanostructures and carbon nanotubes. The study of these materials is accompanied by the development of novel quantum optical devices, whose investigation provides additional information about defects and their role in transport, optical and recombination properties. The experimental work is complemented by theoretical modeling of both the materials and devices. The synergy between experiment and modeling of these materials is one the great strengths of our program

Figure 1: Simulation approaches for the study of Nitride semiconductors.

Nitride Semiconductors: The energy gap of the family of Nitride semiconductors (AlN, GaN and InN) spans the wavelength spectral region from deep ultraviolet to near infrared. Furthermore, by employing intersubband transitions in AlGaN MQWs, this wavelength region can be extended to cover optoelectronic devices operating in the far infrared and terahertz regions of the electromagnetic spectrum. The synthesis of these materials in our Laboratory is carried out by MBE, HVPE and MOCVD. One of the MBE systems has been fitted with a source capable of forming clusters of atoms or molecules by adiabatic expansion and is used for the development of AlN, which is the most refractory of all nitride semiconductors. Another of the MBE systems has been designed to carry out synchrotron-based x-ray studies in real time during film growth (Ludwig).

Moustakas’ group has made seminal contributions in the development of the Nitride semiconductors field. Current activities include the study of growth in-situ, the investigation of InGaN alloys, quantum wells (QWs) and quantum dots (QDs) for the development of green LEDs for solid state lighting, the AlGaN alloys and their QWs for the development of UV emitters, detectors, optical modulators and emitters in the infrared and terahertz spectral regions.

Silicon-based nanostructures: The group of Dal Negro is currently working on: (a) light emission from Si-based nanocrystals; (b) fabrication and design of novel plasmonic devices for sub-diffraction light guidance and control.  The novel possibilities offered by the merging of these two research approaches are also actively investigated, with particular emphasis on innovative design strategies for light emission enhancement and efficient extraction of localized optical fields.

Optical studies of carbon nanotubes: Our objectives in the study of carbon nanotubes fall into three broad categories: electronic properties, vibronic properties, and interactions among quasi-particles. Swan’s group uses resonant Raman scattering to determine the optical (excitonic) transition energies with sub-meV resolution and to study screening effects on the extremely strong Coulomb electron-electron and electron-hole interactions (exciton). The dielectric environment affects the e-e and e-h interactions differently, allowing us to experimentally vary the screening and determine the chirality dependence of these many-body terms.