Research Proposal Funding for the
Solid State Theory Group (NREL)

Description of Funding Sources and Grants
Awarded to the Solid State Theory Group

Sources of Funding

  1. Energy Efficiency (EE) Photovoltaics Office of U.S. Department of Energy --- funding for applied work on photovoltaic semiconductors.
  2. Basic Energy Sciences (BES) Office of Energy Research, Division of Materials Science (DMC) --- funding for basic research on semiconductors, metals, oxides, and method development.

Grants

  1. "Theory for Photovoltaic P.I.ís: A. Zunger, S.H. Wei and S.B. Zhang
    Semiconductors" (PV90) First Funding Year: 1978
    Source: DOE Office of Energy Efficiency Duration: Ongoing

    Provide the fundamental research underpinning the theory of photovoltaic thin-film semiconductors, so as to enhance and accelerate advances in the national photovoltaic technology and R&D program. Objectives for achieving this goal include: (a) studies of the fundamental physical properties of CdS/CdTe alloys, interfaces and impurities; (b) study of defects in ZnO and explore new (including p-type) transparent conductors; (c) explore surface physics and surface defects in CuInSe2; and, (d) maintenance, updating and system administration of the Solid State Theory Computer Network while developing new computational algorithms for larger-scale and more accurate calculations for PV materials. This project is limited to PV absorbers (band gaps 1-1.5eV) and window materials.

  2. "Semiconductor Theory" (ER62) P.I.: A. Zunger
    Source: BES-OER-DMS First Funding Year: 1983
    Duration: Ongoing

    First-Principles band structure, total energy, and statistical mechanical methods are used to predict electronic and structural properties of energy-related semiconductor superlattices, surfaces, alloys and nanostructures, emphasizing chemical trends and properties of new, energy-related materials. Current work includes: (1) prediction of optical and dielectric properties of semiconductor quantum dots, wires, and films including configuration interactions (CdSe, GaAs, InP); (2) first-principles prediction of alloy thermodynamic quantities (e.g., phase-diagrams) for bulk semiconductors and metallic alloys, e.g., CuAu, CuAg, NiAu, AgAu, PdV, CuPd; (3) calculation of electronic properties of novel nitride alloys; and, (4) prediction of properties of unusual ternary materials, e.g., ordered vacancy compounds. Theoretical tools include (a) the total energy non-local pseudopotential method and full-potential linearized augmented plane wave (LAPW) method, (b) the cluster expansion ("LEGO") approach to the Ising program, applied to binary and pseudobinary phase diagrams, and (c) Monte-Carlo and simulated-annealing calculations of Ising models derived from first-principles.

  3. "Growth and Properties of Novel P.I.ís: A. Mascarenhas, J. Olson, A. Zunger
    Ordered Semiconductor Alloys" (ER20) First Funding Year: 1991
    Source: BES-OER-DMS Duration: Ongoing

    This project combines experimental with theoretical efforts aimed at understanding spontaneous long-range order in isovalent III-V/III-V and semiconductor alloys. It includes: (i) MOCVD and MBE growth of III-V alloys such as GaP/InP, A1P/GaP, A1P/InP, A1As/InAs, and GaAs/GaP; (ii) Raman, modulation reflectance photoluminescence, spectroscopic ellipsometry and reflectance difference spectroscopy studies of ordering in the above systems; and, (iii) first-principles theoretical studies of surface-induced, epitaxially-induced and bulk ordering in various alloys, as well as prediction of optical consequences of ordering (polarization anisotropy, band gap narrowing, crystal field splitting, electric fields, band offsets, NMR gradients).

  4. "Atomic and Nanoscale Engineering of P.I.ís: L. Kazmerski, A. Zunger, J. Woodall
    Semiconductors using STM" (ER47) First Funding Year: 1996
    Source: BES-Advanced Energy Projects Duration: 1996-1998

    This project uses a novel method for atomic-scale engineering of semiconductors, leading to advances in understanding and their improvement. It consists of three linked segments: (a) preparation by MBE and MOCVD of State-of-the Art GaInAs and GaInAsP alloys surfaces; (b) use of the novel atomic processing microscope (APM) to image, process (including atom removal and placement) and characterize these semiconductors in the same nanoscale spatial resolutions; and, (c) use of modern electronic structure theory (pseudopotential total energy calculations) to predict the properties of semiconductor surfaces before and after atomic-scale engineering takes place. The program is directed toward the semiconductors GaInAs and GaInAsP, that have applications to solid state and energy technologies, namely thermophotovoltaics. These atomic scale investigations involve the manipulation of atoms in order to study the fundamental defect properties that limit both material properties and device III-V materials, and provides fundamental information of the nature of defects, their electro-optical properties, the ability to electronically heal them with intrinsic and extrinsic atomic species, and further the frontiers of materials science with these novel approaches to investigating material limitations. This project links events on the atomic scale to the current understanding of semiconductor surface properties.

  5. "Composition Modulated Semiconductor Structures P.I.ís: A. Mascarenhas & A. Zunger
    for Photovoltaics and Optical Technologies" (ER60) First Funding Year: 1996
    Source: BES-OER-DMS Duration: Ongoing

    This is a joint project between NREL and Sandia National Laboratories involving the study of spontaneous composition modulation in III-V semiconductor alloys. The main efforts in this program are: (1) MBE growth of III-V ternary alloys and short period superlattices such as InAs/A1As, InAs/GaAs, InP/GaP, which exhibit composition modulation (Sandia); (2) electron microscopy, electron diffraction, x-ray, and atomic force microscopy studies of spontaneously compositionally modulated structures (Sandia and NREL); (3) polarized photoluminescence, ellipsometry, excitation spectroscopy, differential absorption, modulated reflectance, time resolved photoluminescence, and magnetoluminescence studies on spontaneously composition modulated structures; and, (4) theoretical studies on the electronic properties of compositionally modulated alloys - including large-supercell pseudopotential calculations, exploring the way that the composition modulation wavelength, amplitude and direction affects the material properties of otherwise random GaInAs, A1InAs and GaInP alloys (NREL).

  6. "Structurally Tolerant Electronic Oxides" (ER65) P.I.ís: D. Ginley, A. Zunger, T. Ciszek, P. Parilla
    Source: BES-OER-DMS First Funding Year: 1997
    Duration: Ongoing

    Structurally tolerant metal oxides serve as transparent conductors (SnO2, In2O3) in thin film photovoltaics and flat panel displays, as electrochromic layers (WO3) in windows and displays, and as electrodes in high energy density rechargeable Li batteries (V2O5 and LiCO2). Relationship between the structural, electronic and optical properties are studied. We develop a predictive theoretical model of the interplay between structure/doping, and the electronic/optical properties using cluster expansion methods, combined with ab-initio electronic structure.

  7. "Computer-Aided Predictions of Energetics P.I.ís: C. Wolverton & A. Zunger
    and Thermodynamics of Light Metal Alloys" (ER67) First Funding Year: 1997
    Source: BES-OER-PNGV Initiatives Duration: 1997-1999

    Predictions of energetic and thermodynamic properties of light aluminum-based alloys, particularly as they pertain to issues of stability, metastability, structural properties, and states of order (Al-Mg; Al-Cu; Al-Zn). Clarification of the energetics and thermodynamics of these alloys, thereby leading to a more detailed understanding of processes involved in quenching experiments, precipitation kinetics, and ultimately microstructure and processing of these automotive alloys. Properties investigated by a combination of first-principles quantum and statistical mechanical calculations, affording the opportunity of stable and metastable structures, ordered and disordered alloys, and bulk and non-bulk geometries, both at zero and finite temperatures.

  8. "Utilization of Clean Energy by Overcoming Doping P.I.ís: S. Zhang, S.H. Wei, A. Zunger
    Bottlenecks in Semiconductors and Wide Gap Materials" (EROK) First Funding Year: 1999
    Source: BES-OER-CO2 Initiative Duration: Ongoing

    Doping semiconductors and wide-band-gap materials are essential for device applications in clean affordable energy generation and in improved energy efficiency, thus vital for our nationís long-term Carbon management program, as well as for other energy programs. Yet, there are strong doping bottlenecks that may severely restrict potential applications of semiconductors, especially in wide-band-gap materials where bipolar doping is impossible. Recent rapid progress in semiconductor research has reached a point where these doping limitations must be overcome in order to tune semiconductors for precisely required properties. Here, we study what causes the doping bottlenecks by first principles total energy calculations. We base our studies on a set of recent, novel developments regarding the doping limitations: the "doping limit rule" distilled from both phenomenological studies and from first-principles calculations. The doping bottlenecks are identified in this project as due mainly to the formation of intrinsic defects whose formation enthalpies depend on the Fermi energy, and thus always act to negate the effect of doping. We test systematically the various existing microscopic defect models and develop new models to understand the physics of doping. A number of new strategies for overcoming the doping bottlenecks are also studied.