Predicted electronic properties of polycrystalline silicon from three-dimensional device modeling combined with defect-pool model

We assess a broad range of published experiments to show that the density of states (DOS) at high-energy grain boundaries in silicon is appropriately described by the defect-pool model. This implies that the DOS of such grain boundaries depends strongly on the dopant density and on the position of the Fermi level during device processing. However, since high-energy grain boundaries consist of an amorphous layer that is confined to a width of a few angstroms, the DOS is “frozen in” after material processing and does not suffer the strong degradation effects commonly observed in bulk a-Si:H. By combining three-dimensional device modeling and the defect-pool model, we reproduce various test structures and polycrystalline thin-film Si solar cells considerably more precisely than in the past. Our simulation model potentially provides a link between processing conditions and grain boundary quality.

[1]  A. Ghosh,et al.  Hall mobility of polycrystalline silicon , 1980 .

[2]  Tsu-Jae King,et al.  Effective density‐of‐states distributions for accurate modeling of polycrystalline‐silicon thin‐film transistors , 1994 .

[3]  N.C.C. Lu,et al.  A quantitative model of the effect of grain size on the resistivity of polycrystalline silicon resistors , 1980, IEEE Electron Device Letters.

[4]  R. Bube.  ERRATA: ``Interpretation of Hall and Photo‐Hall Effects in Inhomogeneous Materials'' , 1968 .

[5]  Lee,et al.  Atomic and electronic structure of amorphous Si from first-principles molecular-dynamics simulations. , 1994, Physical review. B, Condensed matter.

[6]  A. Bourret,et al.  Atomic structure of grain boundaries in semiconductors , 1987 .

[7]  Andreas Schenk,et al.  Finite-temperature full random-phase approximation model of band gap narrowing for silicon device simulation , 1998 .

[8]  M. J. Powell,et al.  Defect-pool model parameters for amorphous silicon derived from field-effect measurements , 1993 .

[9]  I. Balberg,et al.  Direct determination of the band‐gap states in hydrogenated amorphous silicon using surface photovoltage spectroscopy , 1995 .

[10]  J. Stuchlík,et al.  Microcrystalline Silicon - Relation between Transport and Microstructure , 2001 .

[11]  G. Fortunato,et al.  Field-effect analysis for the determination of gap-state density and Fermi-level temperature dependence in polycrystalline silicon , 1988 .

[12]  N. H. Nickel,et al.  Nature of grain boundaries in laser crystallized polycrystalline silicon thin films , 2001 .

[13]  J. W. Orton,et al.  REVIEW ARTICLE: The Hall effect in polycrystalline and powdered semiconductors , 1980 .

[14]  Hall measurements and grain‐size effects in polycrystalline silicon , 1980 .

[15]  C. Wronski,et al.  Differences in the densities of charged defect states and kinetics of Staebler–Wronski effect in undoped (nonintrinsic) hydrogenated amorphous silicon thin films , 1997 .

[16]  Vaillant,et al.  Recombination at dangling bonds and steady-state photoconductivity in a-Si:H. , 1986, Physical review. B, Condensed matter.

[17]  A model of interface states and charges at the Si‐SiO2 interface: Its predictions and comparison with experiments , 1981 .

[18]  Powell,et al.  Defect-pool model and the hydrogen density of states in hydrogenated amorphous silicon. , 1996, Physical review. B, Condensed matter.

[19]  Broniatowski.  Measurement of the grain-boundary states in semiconductors by deep-level transient spectroscopy. , 1987, Physical review. B, Condensed matter.

[20]  J. Volger,et al.  Note on the Hall Potential Across an Inhomogeneous Conductor , 1950 .

[21]  J. G. Groot,et al.  Grain boundary states and the characteristics of lateral polysilicon diodes , 1982 .

[22]  J. Binder,et al.  Laser‐recrystallized polycrystalline silicon resistors for integrated circuit applications , 1983 .

[23]  W. Read,et al.  Statistics of the Recombinations of Holes and Electrons , 1952 .

[24]  H. Foll,et al.  TEM observations on grain boundaries in sintered silicon, part 1 , 1978 .

[25]  N. Nickel.  Hydrogen-induced defects in polycrystalline silicon , 1996 .

[26]  T. Makino,et al.  The influence of plasma annealing on electrical properties of polycrystalline Si , 1979 .

[27]  C. D'anterroches,et al.  Atomic structure of [011] and [001] near-coincident tilt boundaries in germanium and silicon , 1984 .

[28]  Cohen,et al.  Density of states for an electron in a correlated Gaussian random potential: Theory of the Urbach tail. , 1988, Physical review. B, Condensed matter.

[29]  Y. Hamakawa,et al.  Amorphous silicon technology , 1988 .

[30]  R. P. Ruth,et al.  Dependence of electrical properties of polycrystalline cvd si films on grain size and impurity doping concentrationa,b , 1981 .

[31]  J. Bruyère,et al.  Recombination at dangling bonds and band tails: Temperature dependence of photoconductivity in hydrogenated amorphous silicon , 1988 .

[32]  M. Hirose,et al.  Energy distribution of trapping states in polycrystalline silicon , 1980 .

[33]  W. Füssel,et al.  Defects at the Si/SiO2 interface: Their nature and behaviour in technological processes and stress , 1996 .

[34]  K. Saraswat,et al.  Determination of the densities of gap states in hydrogenated polycrystalline Si and Si0.8Ge0.2 films , 1992 .

[35]  D. Thomson,et al.  Thermionic‐field emission from interface states at grain boundaries in silicon , 1984 .

[36]  D. Macdonald,et al.  Trapping of minority carriers in multicrystalline silicon , 1999 .

[37]  J. Hornstra.  Models of grain boundaries in the diamond lattice I. Tilt about I 10 , 1959 .

[38]  N. Blum,et al.  Vacuum-deposited polycrystalline silicon solar cells on foreign substrates , 1982 .

[39]  C. Soukoulis,et al.  Band tails, path integrals, instantons, polarons, and all that , 1988 .

[40]  Werner,et al.  Exponential band tails in polycrystalline semiconductor films. , 1985, Physical review. B, Condensed matter.

[41]  S. Hasegawa,et al.  Plasma‐hydrogenation effects on conductivity and electron spin resonance in undoped polycrystalline silicon , 1982 .

[42]  T. Umeda,et al.  Electron-spin-resonance center of dangling bonds in undoped a-Si:H , 1999 .

[43]  J. Rath,et al.  Purely Intrinsic Poly-silicon Films for n-i-p Solar Cells , 1997 .

[44]  J. Hirth,et al.  Structure of twin boundaries with added tilt and twist in silicon , 1989 .

[45]  W. Füssel,et al.  Capture cross sections of defect states at the Si/SiO2 interface , 2000 .

[46]  C. Wronski,et al.  Differences between light induced and native midgap states in intrinsic hydrogenated amorphous silicon obtained from detailed modeling of photoconductivities and subband‐gap absorption , 1992 .

[47]  E. Schiff,et al.  Direct observation of dangling bond motion in disordered silicon , 1998 .

[48]  W. V. Roosbroeck.  Theory of the flow of electrons and holes in germanium and other semiconductors , 1950 .

[49]  M. J. Powell,et al.  Temperature dependence of intergrain barriers in polycrystalline semiconductor films , 1980 .

[50]  M. Martínez-Hernández,et al.  Deformation mechanisms of Σ = 9 bicrystals of silicon , 1987 .

[51]  L. Colombo,et al.  Correlation between atomic structure and localized gap states in silicon grain boundaries , 1998 .

[52]  S. Krishnaswamy,et al.  Black a‐Si solar selective absorber surfaces , 1980 .

[53]  P. Altermatt,et al.  Assessment and parameterisation of Coulomb-enhanced Auger recombination coefficients in lowly injected crystalline silicon , 1997 .

[54]  J. Seto.  The electrical properties of polycrystalline silicon films , 1975 .

[55]  C. H. Seager,et al.  Grain boundary states and varistor behavior in silicon bicrystals , 1979 .

[56]  Y. Taga,et al.  Formation process of interface states at grain boundaries in sputtered polycrystalline Si films , 1999 .

[57]  M. J. Powell,et al.  Dangling-bond defect state creation in microcrystalline silicon thin-film transistors , 2000 .

[58]  Electrical properties of cw laser‐annealed ion‐implanted polycrystalline silicon , 1980 .

[59]  Powell,et al.  Defect pool in amorphous-silicon thin-film transistors. , 1992, Physical review. B, Condensed matter.

[60]  J. Heleskivi,et al.  On the Hall Voltage in an Inhomogeneous Material , 1972 .

[61]  C. H. Seager,et al.  Direct measurement of electron emission from defect states at silicon grain boundaries , 1979 .

[62]  J. Simmons,et al.  Basic equations for statistics, recombination processes, and photoconductivity in amorphous insulators and semiconductors , 1972 .

[63]  R. Street,et al.  Effects of doping on transport and deep trapping in hydrogenated amorphous silicon , 1983 .

[64]  J. B. Adams,et al.  Energetics of hydrogen in amorphous silicon: An ab initio study , 1998 .

[65]  H. K. Charles,et al.  Evaporated polycrystalline silicon films for photovoltaic applications - grain size effects , 1978 .

[66]  S. Yamasaki,et al.  Temperature dependence of electron-capture cross section of localized states in a − S i : H , 1983 .

[67]  K. Bube,et al.  Values of capture cross sections of metastable defects in hydrogenated amorphous silicon , 1996 .

[68]  J. J. Yang,et al.  Grain‐size effects on electrical properties of n‐type polycrystalline chemical vapor deposition Si films , 1984 .

[69]  C. H. Seager,et al.  The determination of grain‐boundary recombination rates by scanned spot excitation methods , 1982 .

[70]  G. Pike,et al.  Anomalous low-frequency grain-boundary capacitance in silicon , 1980 .

[71]  Pantelides.  Defects in amorphous silicon: A new perspective. , 1986, Physical review letters.

[72]  W. E. Taylor,et al.  Grain Boundary Barriers in Germanium , 1952 .

[73]  J. Piqueras,et al.  Electronic properties of undoped polycrystalline silicon , 1974 .

[74]  R. Hall.  Electron-Hole Recombination in Germanium , 1952 .

[75]  T. Chu,et al.  Deposition and Properties of Silicon on Graphite Substrates , 1976 .

[76]  Krishna C. Saraswat,et al.  Phosphorus Doping of Low Pressure Chemically Vapor‐Deposited Silicon Films , 1979 .

[77]  Werner,et al.  Deep-level-noise spectroscopy of ion-implanted polysilicon thin films. , 1988, Physical Review B (Condensed Matter).

[78]  C. H. Seager,et al.  The dc voltage dependence of semiconductor grain‐boundary resistance , 1979 .

[79]  Biegelsen,et al.  Dangling or floating bonds in amorphous silicon? , 1988, Physical review letters.

[80]  R. Petritz.  Theory of an Experiment for Measuring the Mobility and Density of Carriers in the Space-Charge Region of a Semiconductor Surface , 1958 .

[81]  G. Fortunato,et al.  Determination of gap state density in polycrystalline silicon by field‐effect conductance , 1986 .

[82]  E. Pincik,et al.  EVIDENCE FOR THE IMPROVED DEFECT-POOL MODEL FOR GAP STATES IN AMORPHOUS SILICON FROM CHARGE DLTS EXPERIMENTS ON UNDOPED A-SI:H , 1997 .

[83]  Carlsson,et al.  Energy levels and charge distributions of nonideal dangling and floating bonds in amorphous Si. , 1989, Physical review. B, Condensed matter.

[84]  C. H. Seager,et al.  Grain boundary recombination: Theory and experiment in silicon , 1981 .

[85]  K. Arai,et al.  Rapid Quenched Ribbon-Form Silicon , 1980 .

[86]  Werner,et al.  Non-Lorentzian noise at semiconductor interfaces. , 1985, Physical Review Letters.

[87]  L. Kazmerski,et al.  Chemical, compositional, and electrical properties of semiconductor grain boundaries , 1982 .

[88]  P. Altermatt,et al.  Development of a three-dimensional numerical model of grain boundaries in highly doped polycrystalline silicon and applications to solar cells , 2002 .

[89]  J. Werner.  Origin of Curved Arrhenius Plots for the Conductivity of Polycrystalline Semiconductors , 1994 .

[90]  S. Iyer,et al.  Grain-boundary states and hydrogenation of fine-grained polycrystalline silicon films deposited by molecular beams , 1991 .

[91]  Conduction mechanism of high-resistivity polycrystalline silicon films , 1985 .

[92]  Wang,et al.  Electronic structure of dangling and floating bonds in amorphous silicon. , 1989, Physical review letters.

[93]  T. Castner,et al.  Zero‐bias resistance of grain boundaries in neutron‐transmutation‐doped polycrystalline silicon , 1978 .

[94]  E. Morgado.  Recombination at correlated dangling bonds and the effects of Fermi level position on steady-state photoconductwiry in amorphous silicon , 1991 .

[95]  C. H. Seager.  Temperature dependence of minority‐carrier recombination velocities at grain boundaries in silicon , 1982 .

[96]  Balberg,et al.  Evidence for the defect-pool model from induced recombination level shifts in undoped a-Si:H. , 1993, Physical review. B, Condensed matter.

[97]  D.B.M. Klaassen,et al.  A unified mobility model for device simulation—I. Model equations and concentration dependence , 1992 .

[98]  R. Sinton,et al.  On the use of a bias-light correction for trapping effects in photoconductance-based lifetime measurements of silicon , 2001 .

[99]  Car,et al.  Amorphous silicon studied by ab initio molecular dynamics: Preparation, structure, and properties. , 1991, Physical review. B, Condensed matter.

[100]  H. Okamoto,et al.  Electronic behaviors of the gap states in amorphous semiconductors , 1977 .

[101]  Warren B. Jackson,et al.  Density of gap states of silicon grain boundaries determined by optical absorption , 1983 .

[102]  N. Johnson,et al.  Hydrogen-induced metastable changes in the electrical conductivity of polycrystalline silicon , 1994 .

[103]  D. Thomson,et al.  Electronic transport at grain boundaries in silicon , 1983 .

[104]  H. Kuwano,et al.  Energy distribution of trapping states at grain boundaries in polycrystalline silicon , 1992 .

[105]  A. Baldereschi,et al.  Coordination defects in amorphous silicon and hydrogenated amorphous silicon: A characterization from first-principles calculations , 2000 .

[106]  F. Cleri.  Atomic and electronic structure of high-energy grain boundaries in silicon and carbon , 2001 .

[107]  R. Bube,et al.  Interpretation of Equilibrium and Steady-State Hall and Thermoelectric Effects in Inhomogeneous Materials , 1970 .

[108]  David Alan Drabold,et al.  Defects, tight binding, and first-principles molecular-dynamics simulations on a-Si. , 1992, Physical review. B, Condensed matter.

[109]  C. Wronski,et al.  Effect of midgap states in intrinsic hydrogenated amorphous silicon on sub‐band‐gap photoconductivity , 1991 .

[110]  A. Hourd,et al.  The temperature dependence of the D° and D+ capture cross-section in a-Si , 1985 .

[111]  M. Green,et al.  Spatially resolved analysis and minimization of resistive losses in high-efficiency Si solar cells , 1996 .

[112]  M. Stutzmann,et al.  Occupancy of dangling bond defects in doped hydrogenated amorphous silicon , 1987 .

[113]  S. Phillpot,et al.  Grain boundaries in silicon from zero temperature through melting , 1988 .

[114]  T. Mcmahon,et al.  Charged defect states in intrinsic hydrogenated amorphous silicon films , 1994 .

[115]  J. Werner,et al.  Density of states of grain boundaries in silicon , 1982 .

[116]  M. Caymax,et al.  Polysilicon Thin-Film Solar Cells: Influence of the Deposition Rate upon Enhanced Diffusion and on Cell Performance , 2001 .

[117]  Computer simulation of the effect of phosphorous doping of the i-layer in a thin-film a-Si:H p–i–n solar cell , 2000 .

[118]  J. Simmons,et al.  Nonequilibrium Steady-State Statistics and Associated Effects for Insulators and Semiconductors Containing an Arbitrary Distribution of Traps , 1971 .

[119]  Powell,et al.  Improved defect-pool model for charged defects in amorphous silicon. , 1993, Physical review. B, Condensed matter.

[120]  Enhanced conductivity in plasma‐hydrogenated polysilicon films , 1980 .

[121]  J. Palm.  Local investigation of recombination at grain boundaries in silicon by grain boundary‐electron beam induced current , 1993 .

[122]  L. H. Slack,et al.  Resistivity of Doped Polycrystalline Silicon Films , 1973 .

[123]  Van de Walle Cg,et al.  ENERGETICS OF BOND-CENTERED HYDROGEN IN STRAINED SI-SI BONDS , 1995 .

[124]  Ch. Hof,et al.  MOBILITY LIFETIME PRODUCT : A TOOL FOR CORRELATING A-SI:H FILM PROPERTIES AND SOLAR CELL PERFORMANCES , 1996 .

[125]  Giorgio Baccarani,et al.  Transport properties of polycrystalline silicon films , 1978 .

[126]  Dominique Vuillaume,et al.  TEMPERATURE-DEPENDENT STUDY OF SPIN-DEPENDENT RECOMBINATION AT SILICON DANGLING BONDS , 1994 .

[127]  D. Dumin.  Deep levels within the forbidden gap of silicon-on-sapphire films , 1970 .

[128]  Electron Transport Mechanisms in Nickel Schottky Barrier Contacts to Hydrogenated Amorphous Silicon , 1992 .

[129]  S. Pantelides.  Defects in Amorphous Silicon , 1991 .

[130]  S. Phillpot,et al.  On the Thermodynamic Stability of Amorphous Intergranular Films in Covalent Materials , 1997 .

[131]  Y. Okayasu,et al.  Fabrication of poly-crystalline silicon films using plasma spray method , 1994 .

[132]  W. V. Roosbroeck,et al.  The Transport of Added Current Carriers in a Homogeneous Semiconductor , 1953 .