The science and engineering of materials and device structures at the nanometer scale have become central themes in fields ranging from solid-state electronics and photonics to the biological sciences. As a result, the characterization, understanding, and control of material and device properties at the nanometer to atomic scale have emerged as essential aspects of materials and device engineering. We will discuss some recent results from our laboratory directed towards the imaging, analysis, and application of nanoscale phenomena in variety of solid-state m aterials and devices. In the area of III-nitride semiconductor heterostructures and devices, we show how scanned probe imaging of electronic structure in InGaN/GaN quantum-well heterostructures reveals nanoscale variations in carrier accumulation behavior associated with monolayer thickness fluctuations and the presence of nanoscale In-rich clusters within InGaN quantum wells. These variations can be correlated with, and explain, differences in luminescence intensity among various nitride-based light emitting diode structures. In the area of high-efficiency photovoltaics, we discuss approaches for design and fabrication of quantum-well solar cells that exploit plasmonic effects and light scattering by metal and dielectric nanostructures integrated with the semiconductor device structure. We show that these approaches lead to substantial improvements in power conversion efficiency with the potential to enable realization of extremely thin, highly efficient solar cells and related devices.
Wednesday, April 08, 2009
Free and open to the public