Disordered Semiconductors

Twenty-four years ago, Hellmut Fritzsche came to our laboratory to evaluate our work in amorphous materials. He came many times, sometimes bringing his violin to play with our youngest son, to talk, to help, to discover, and to teach. The times with him were always exciting and rewarding. There was a camaraderie in the early years that has continued and a friendship that has deepened among Iris and me and Hellmut, Sybille and their children. The vision that Hellmut Fritzsche shared with me, the many important contributions he made, the science that he helped so firmly to establish, the courage he showed in the time of our adversity, and the potential that he recognized put all of us in the amorphous field, not only his close friends and collaborators, in his debt. He helped make a science out of intuition, and played an important role not only in the experimental field but also in the basic theoretical aspects. It has been an honor to work with Hellmut through the years.

One: The Metal-Nonmetal Transition.- Impurity Bands in Silicon and Germanium.- Critical Phenomena Near the Metal-Insulator Transition.- The Metal-Insulator Transition at Millikelvin Temperatures.- Magnetic Field Induced Transitions in Disordered Metals.- Compensation Tuning Study of Metal Insulator Transition in Si:P.- The Metal-Insulator Transition in Compensated Silicon.- The Spectroscopic Investigation of Negatively Charged Donor Ions (D-States).- Magnetic Properties of Donors and Acceptors in Silicon: Similarities and Differences.- The AC Conductivity in n-Type Silicon Below the Metal- Insulator Transition.- Low Frequency Conductivity Anomalies of Strongly Disordered Semiconductors.- Inelastic Scattering Time of Electrons in Metallic Ge:Sb.- Localization Effects in Quasi-One-Dimensional Lithium Quench-Condensed Micro structures.- Potential Disorder in Granular Metals.- X-Ray and Neutron Scattering Studies of Graphite Intercalated with Two-Dimensional K-NH3Metal-Ammonia Solutions.- Pressure-Induced Effects on Phonons and Gap States in Alloy Semiconductors.- The Superconductor-Semiconductor Transition in Cation-Substituted Lithium Titanate, Li[MxTi2-x]04:M = Li+, Al3+, and Cr3+.- Two: Optical and Electronic Phenomena in Amorphous Chalcogenide Semiconductors.- Photoinduced and Radiation-Induced Structural Transformations in Vitreous Arsenic Chalcogenides.- New Aspects of Photoinduced Paramagnetic States in Chalcogenide Glasses.- On the Relationship Between ESR and Photodarkening in Glassy AS2S3.- Photo-Induced Effects in Amorphous Ge-S.- Polarization Memory of Photoluminescence and Photoinduced Optical Anisotropy in Chalcogenide Glasses.- The Quantum Nature of Amorphous Solids.- Changes in the Photoelectronic Properties of Glassy Chalcogenides Induced by Chemical Doping, Irradiation, and Thermal History.- A Model for the Electrical Doping of Chalcogenide Glasses by Bismuth.- Current Transient Studies of Al-a-As2Se3Contacts.- Optical Determination of the Fundamental Energy Gap of Amorphous M0S3.- Three: Structure and Bonding in Amorphous Semiconductors.- Structure of Amorphous Semiconductors.- The Sillium Model.- High Brilliance X-Ray Sources and the Study of Amorphous Materials.- X-Ray Absorption Studies of Amorphous Arsenic Chalcogenide Semiconductors.- Structural Order and Dynamics of Noncrystalline Condensed Matter.- Investigation of Medium Range Order by Photo-emission, Reflectivity, Laser-Induced Crystallization Raman Spectroscopy in Amorphous GeSe2.- Bonding and Short Range Order in a-GexTe1-xAlloys.- Refractive Index Dispersion and Structure of Chalcogenide Glasses.- Spectroscopic Ellipsometry Studies of Void Structure in Obliquely Deposited Amorphous Ge Films.- Four: Transient, Photoexcited and Spin Phenomena in Tetrahedral Amorphous Semiconductors.- Picosecond Photomodulation Studies of Carrier Trapping in a-Si:H.- Photoluminescence Studies of Band-Tail States in a-Si:H.- Recombination in a-Si:H Based Materials: Evidence for Two Slow Radiative Processes.- Thermal and Optical Quenching of the Photo- conductivity in a-Si:H-Films.- Recombination and the Standard Model in Amorphous Hydrogenated Silicon (a-Si:H): An Essay.- An Extension of Einstein’s Treatment of Spontaneous Emission.- Optical and Photoelectrical Properties of a-Si:H Implanted By Mg Ions.- Determination of the Electronic Density of States of n-Type Hydrogenated Amorphous Silicon from Transient Sweep-Out Experiments.- Electron Correlation Energies in Hydrogenated Amorphous Silicon.- Defects in a-Si:H..- Five: Preparation and Characterization of Tetrahedral Amorphous Semiconductors.- Optical Absorption Edge of Hydrogenated Amorphous Silicon.- Preparation of a-Si and Its Related Materials by Hydrogen Radical Enhanced CVD.- Application of In Situ Ellipsometry to the Growth of Hydrogenated Amorphous Silicon.- Density of Gap States in Undoped and Doped Amorphous Hydrogenated Silicon Obtained by Optical Spectroscopy.- Structural and Electronic Properties of Polymeric Amorphous Semiconductors Si1-xCx:H.- Structural Characterization of Amorphous Silicon and Germanium.- Electrical Conductivity of Non-Hydrogenated Amorphous Tetracoordinated Semiconductors.- DC Electrical Conductivity of Highly Disordered Elemental Semiconductors.- Six: Multilayers and Interfaces.- Resonant Tunneling Through Quantized States in a-Si:H x.- Persistent Photoconductivity in Amorphous Silicon Alloys.- The Thermal Equilibration Model for Persistent Photoconductivity in Doping Modulated Amorphous Silicon.- Band Edge Alignment and Quantum Size Effects in Hydrogenated Amorphous Silicon/ Germanium Superlattice Structures.- Carrier Recombination Kinetics in Amorphous Doping Superlattices.- Material Design by Structural Modulation of Amorphous Semiconductors.- Junction Capacitance Studies of Hydrogenated Amorphous Silicon Doping Superlattice Films.- The Effects of Band Bending on the Optical, Electrical, and Photoelectronic Properties of a-Si:H Thin Films in Surface Cell Structures.- Effect of Band Tails on the Electric Field of Amorphous Silicon Solar Cells.- Seven: Stability Of a-Si.- Hydrogen Motion and the Staebler-Wronski Effect in Amorphous Silicon.- Elimination of Photo-Induced Degradation in Semiconductor Devices.- Dangling Bonds and Metastability in Semiconductors.- Recombination-Enhanced Defect Formation and Annealing in a-Si:H.- Composition and Thermal Stability of Glow- Discharge a-Si:C:H and a-Si:N:H Alloys.- Investigation of the Electronic Structure of Amorphous Silicon Based on Studies of the Amorphous-to-Crystalline Transition.- Eight: Theories and Models for The Electronic Properties of Amorphous Semiconductors.- Theory of Covalent Amorphous Semiconductors.- Tails in the Density of States.- Localization Effects in Amorphous Semiconductors.- Band-Edge Conduction in Amorphous Semiconductors.- The Statistical Shift of the Fermi Energy and the Prefactor of the DC Conductivity in a-Si:H.- Luminescence and Relaxation of Energy in Disordered Organic and Inorganic Materials.- Thermoelectric Power of Anderson-Mott Insulators with an Exponential Density of States Distribution.- Dramatic Effects of Disorder on Small-Polaron Formation and Motion.- Author Index.