Effect of Grain Boundary Segregation on the Transbarrier Conductivity of Polycrystalline Silicon (original) (raw)
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A model for conduction in polycrystalline silicon—Part II: Comparison of theory and experiment
IEEE Transactions on Electron Devices, 1981
A new phenomenological model for the electrical conduction in polycrystalline silicon is developed. The combined mechanisms of dopant segregation, carrier trapping, and carrier reflection at grain boundaries are proposed to explain the electrical conduction in polycrystalline silicon. The grain boundaries are assumed to behave as an intrinsic wide-band-gap semiconductor forming a heterojunction with the grains. Thermionic emission over the potential barriers created within the grains due to carrier trapping at the grain boundaries and then tunneling through the grain boundaries is proposed as the carrier transport mechanism. A generalized current-voltage relationship is developed which shows that the electrical properties of polycrystall i e silicon depend on the properties of the grain boundaries.
Solar Cells, 1983
In this article the properties of grain and twin boundaries in polycrystalline silicon layers grown by the ribbon-against-drop process are reported; the thermal diffusion of phosphorus, the electrical activity of these defects and their passivation by hydrogen are discussed. Autoradiography experiments did not evidence any significant intergranular diffusion of phosphorus; crossed electron-beam-induced current (or light-beam-induced current) and autoradiography experiments strongly suggest that the recombination at grain and twin boundaries is dominated by impurities. Finally, it is shown that the hydrogen passivation is associated with retarded diffusion and large segregation effects.
Carrier Transport across a Few Grain Boundaries in Highly Doped Polycrystalline Silicon
Japanese Journal of Applied Physics, 2001
We have fabricated nanometer-scale point-contact devices in 50-nm-thick poly-Si films with a grain size of from 150 nm to 20 nm. Both linear and nonlinear I ds-V ds characteristics were observed in these devices, corresponding to a channel without a grain boundary (GB) and that with a single or a few GBs, respectively. The temperature dependence of resistivity indicated that the effective potential barrier height qV B of the GBs for the devices which show the nonlinear I ds-V ds characteristics ranges from 30 meV to 80 meV. We discussed percolation conduction of electrons through a few GBs due to nonuniform GB properties in heavily doped poly-Si films.
Carrier transport across few grain boundaries in highly doped polycrystalline silicon
Japanese Journal of Applied Physics, 2001
We have fabricated nanometer-scale point-contact devices in 50-nm-thick poly-Si films with a grain size of from 150 nm to 20 nm. Both linear and nonlinear I ds-V ds characteristics were observed in these devices, corresponding to a channel without a grain boundary (GB) and that with a single or a few GBs, respectively. The temperature dependence of resistivity indicated that the effective potential barrier height qV B of the GBs for the devices which show the nonlinear I ds-V ds characteristics ranges from 30 meV to 80 meV. We discussed percolation conduction of electrons through a few GBs due to nonuniform GB properties in heavily doped poly-Si films.
Conductivity anisotropy ofn-type silicon in the range of warm and hot carriers
Zeitschrift f�r Physik, 1965
The electric conductivity of n-type silicon was measured as a function of the field intensity in different crystallographic directions at temperatures between 78 and 275 ~ From the data at medium fields (range of warm carriers) the coefficients t0 and Y0 of SCHMIDT-TIEDEMANN'S anisotropy theory were determined. Especially at low temperatures these coefficients are different for lightly and heavily doped crystals. The differences can be explained by the influence of ionized impurity scattering in addition to lattice scattering. The repopulation of the energy valleys of the conduction band as a function of the field intensity was calculated from the ratio 70/to and-in the range of hot carriers-from the conductivities measured in (001) and (111) directions. A maximum increase of population of a cool valley was found to be between 0.5 and 1.2 of the zero-field population, depending on the particular sample, the field intensity being about 0.5 kV/cm and the lattice temperature 89 ~
Electrical and Structural Properties of Grain Boundary in Polycrystalline Si
MRS Proceedings, 1981
ABSTRACTA special type of high angle grain boundary with mirror symmetry of the crystallographic orientation between the two grains is examined electrically and structurally. Transmission electron microscopy investigations show the nonuniform nature of the grain boundary. Both coherent and incoherent regions are observed along the boundary plane, and the types of dislocations and their densities vary from place to place. Electrical measurements of the boundary properties indicate no measurable barrier height. Heat treatment of the sample in an oxygen atmosphere at 950°C for 30 min did not change the boundary resistance. However, recombination effects are enhanced after boron diffusion. When pulsed laser radiation was used to process this material, it was found that the grain boundary structures were modified by laser-induced surface melting, i.e., incoherent boundaries were converted to coherent boundaries in the melted region.
Electrical activity of extended defects in polycrystalline silicon
1988
2014 On étend l'analyse de la relation entre microstructure du silicium polycristallin et longueur de diffusion des porteurs minoritaires en y incluant l'influence du carbone et de l'oxygène, deux impuretés dont on connaît l'effet sur l'activité électrique des dislocations et des joints de grain. On trouve qu'un terme de la forme ND . (NO-NC), où ND est la densité de dislocations et No, NC les concentrations respectives d'oxygène et de carbone, rend bien compte de l'influence de ces deux impuretés sur la longueur de diffusion des porteurs minoritaires. 11 en résulte que cette influence n'est que marginale et que la recombinaison aux joints de grain dépend presqu'exclusivement des dislocations. Abstract. 2014 The analysis of the dependence of the diffusion length of minority carriers on the microstructure in polycrystalline silicon has been extended by considering the influence of oxygen and carbon. These impurities are in fact known to have a definite effect on the electrical activity of dislocations and grain boundaries (GB). The results of this analysis show that a term of the type ND(NO-NC), where ND is the dislocation density and NO, NC are the concentration of oxygen and carbon, respectively, well accounts for the influence of oxygen and carbon on the diffusion length of minority carriers. Oxygen and carbon, therefore, affect only marginally the recombination losses at GB in polycrystalline silicon, whose average diffusion length is determined almost exclusively by dislocations.
Some controversial points related to transport in microcrystalline silicon
2009
We have compared the results of effective medium theories with the d.c. dark electrical conductivity for a number of undoped thin film Si series crossing the amorphous/microcrystalline transition. All series exhibited the percolation threshold at 70-80 % crystallinity, i.e., at values higher than expected for a random mixture. We explain this observation by a resistive coating of the crystalline grains, which presents a limiting step for transport. We identify this coating with the Large Grain Boundaries (LGB) from our previously formulated model of transport. The LGBs consist of an amorphous Si based tissue with a band gap increased due to H and O alloying, to which also most of the defects concentrate. The apparent paradox of higher room temperature conductivity resulting from the formation of LGBs is explained, too. Our microscopic measurements of conductivity with an AFM tip are consistent with this model if care is taken to avoid artifacts related to tip induced oxidation of the sample surface.
2021
In monocrystalline structures, their structural properties determine thermal and electrical ones. Here, the effect of defects induced by intrinsic and extrinsic parameters on the thermal and electrical properties during manufacturing processes and samples preparation in p-type Si wafers with different carrier concentrations was investigated. Photoacoustic technique and thermal relaxation method sensed local variations in the thermal diffusivity and volumetric heat capacity, respectively. These variations are due to the local changes in the defect density produced by polishing processes and doping inclusion. The Hall effect sensed the effective carrier lifetime changes by the presence of defects in the crystalline structure. The carrier distribution was determined by photothermal and photocarrier images allowing to see local variations in the boron distribution. The crystalline quality obtained by studying the FWHM of the X-Ray diffraction patterns elucidated the effect of samples polishing and preparation on the thermal properties
Modeling of Poly-Silicon Carrier Transport with Explicit Treatment of Grains and Grain Boundaries
VLSI Design, 1998
Explicit treatment of grains and grain boundaries is necessary to model the carrier transport in poly-silicon devices whose feature size is comparable to the grain size. The grain boundaries were modeled by interface traps, and comparison was made between thermionic and diffusion transport across the grain boundaries. It was found that the numerical model for diffusion transport with total trap conservation in grain boundary areas is not physically convergent and shows a strong grid sensitivity. Effects of the critical doping level and the lattice temperature are demonstrated on poly-silicon resistors with 1-D bamboo-type and 2-D realistic microstructures.