1. We use synchrotron-radiation based spectroscopies to measure the electronic structure of wide band gap semiconductors. Our goal is to understand how this structure effects the growth of these materials, the growth of contact overlayers, and the chemical stability of the films and overlayers. These materials have numerous applications in optoelectronic devices. Despite intense study, much remains unknown about their fundamental physical and chemical properties. The results of our recent studies of InN are reported here. We have observed for the first time quantum well (QW) states at the surface of InN (0001) due to electron accumulation. Figure 1 presents an angle resolved photoemission (ARPES) intensity plot from InN. The parabolic nature of the states near the Fermi level is clearly visible. We can now controllably generate surfaces with anywhere between 2 and 5 QW states. Figure 2 presents the first ARPES measurement of a Fermi surface for such states. These are remarkable observations, and analysis and further experiments are underway. Synchrotron Radiation Spectroscopic Study of Surface and Bulk Electronic Structure of Wide Band Gap Semiconductors Kevin E. Smith, Boston University, DMR- 0311792 Figure 1: High resolution ARPES intensity map showing the first observation of quantum well free electron-like states at the surface of InN At least three well-defined states are visible, each exhibiting a perfectly parabolic dispersion. Surfaces with 2, 3, 4, and 5 such states can be prepared. Note that the bulk band gap of InN is 0.77 eV, and these states lie well in the conduction band. (Data taken at the National Synchrotron Light Source, Beamline U5UA)

2. Educational Activities: This program involves the education of two graduate students (Leyla Colakerol, and Alex DeMasi) and one postdoctoral research associate (Dr. Lukasz Plucinski). Note also that the PI has finished a two year appointment as the first Academic Director of the Center for Excellence in Teaching at Boston University. Furthermore, the PI was named the 2001 Massachusetts Professor of the Year by the Carnegie Foundation. Infrastructure Impact: The PI used the present NSF award to leverage significant funds for scientific infrastructure enhancement. He was awarded $50,000 from the Defense University Research Instrumentation Program of the Army Research Office to purchase an Electron Cyclotron Resonance plasma source. This is attached to our multi-technique spectrometer system based at the National Synchrotron Light Source, and will be used to clean ternary nitride alloy thin films. Our spectrometer system is fully operational and features both a high resolution angle resolved photoemission spectrometer (100 mm Scienta), and a high resolution soft x-ray emission spectrometer. Synchrotron Radiation Spectroscopic Study of Surface and Bulk Electronic Structure of Wide Band Gap Semiconductors Kevin E. Smith, Boston University, DMR- 0311792 Figure 2: Fermi surface and constant energy contours from a 2-state InN accumulation layer. The Fermi surface consists of two perfectly concentric circular structures, one from each band crossing the Fermi level, E F. As the bands are sliced away from E F, constant energy contours are generated, and these remain perfectly circular to the bottom of the respective bands. No interaction of these electrons with the periodic crystal lattice is visible. (Data taken at the Advanced Light Source, Beamline 12)