Conduction in Polycrystalline Silicon: Generalized Thermionic Emission-Diffusion Theory and Extended State Mobility Model

ABSTRACTWe present a general theory of conduction in polysilicon. The theoretical framework reconciles two apparently divergent approaches for modeling conduction processes in polysilicon and provides a physical basis to correctly interpret and to point out the deficiencies of previously reported thermionic and thermionic field emission theory. This model is based on an extended state mobility in the disordered grain boundary and the thermionic emission-diffusion theory for conduction of current. The attractive features of our theory are (a) it can explain the experimental data without the use of an artificial factor, f, (b) the conduction process is characterized explicitly by the inherent material properties of the grain and the grain boundary. Our model is particularly suited for describing the electrical properties of laser restructured polysilicon, where because of large grain size the diffusion process is expected to be dominant.

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Conduction in polycrystalline silicon: Diffusion theory and extended state mobility model

IEEE Electron Device Letters ◽

10.1109/edl.1982.25514 ◽

1982 ◽

Vol 3 (5) ◽

pp. 141-143 ◽

Cited By ~ 22

Author(s):

D.M. Kim ◽

A.N. Khondker ◽

R.R. Shah ◽

D.L. Crosthwait

Keyword(s):

Polycrystalline Silicon ◽

Diffusion Theory ◽

Mobility Model ◽

Extended State ◽

Silicon Diffusion

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The Influence of Grain-Boundary Recombination and Grain Size on the I(V)-Characteristics of Polycrystalline Silicon Solar Cells

Fourth E.C. Photovoltaic Solar Energy Conference ◽

10.1007/978-94-009-7898-0_84 ◽

1982 ◽

pp. 516-521

Author(s):

M. Böhm ◽

R. Kern ◽

H. G. Wagemann

Keyword(s):

Grain Size ◽

Solar Cells ◽

Grain Boundary ◽

Polycrystalline Silicon ◽

Silicon Solar Cells

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Carrier Transport in Ultra-Thin Nano/Polycrystalline Silicon Films and Nanowires

MRS Proceedings ◽

10.1557/proc-664-a16.2 ◽

2001 ◽

Vol 664 ◽

Cited By ~ 1

Author(s):

Toshio Kamiya ◽

Yong T. Tan ◽

Yoshikazu Furuta ◽

Hiroshi Mizuta ◽

Zahid A.K. Durrania ◽

...

Keyword(s):

Grain Boundary ◽

Polycrystalline Silicon ◽

Carrier Transport ◽

Crystalline Silicon ◽

Thermionic Emission ◽

Nanocrystalline Silicon ◽

Silicon Films ◽

Si Nanowires ◽

Potential Barriers ◽

Boundary Potential

ABSTRACTCarrier transport was investigated in two different types of ultra-thin silicon films, polycrystalline silicon (poly-Si) films with large grains > 20 nm in size and hydrogenated nanocrystalline silicon (nc-Si:H) films with grains 4 nm – 8 nm in size. It was found that there were local non-uniformities in grain boundary potential barriers in both types of films. Single-electron charging effects were observed in 30 nm × 30 nm nanowires fabricated in 30 nm-thick nc-Si:H films, where the electrons were confined in crystalline silicon grains encapsulated by amorphous silicon. In contrast, the poly-Si nanowires of similar dimensions showed thermionic emission over the grain boundary potential barriers formed by carrier trapping in grain boundary defects.

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Ion Implantation Doping of Semi-Insulating Polycrystalline Silicon

MRS Proceedings ◽

10.1557/proc-316-307 ◽

1993 ◽

Vol 316 ◽

Author(s):

Salvatore Lombardo ◽

S. U. Campisano

Keyword(s):

Grain Boundary ◽

Polycrystalline Silicon ◽

Room Temperature ◽

Thermionic Emission ◽

Threshold Value ◽

Threshold Level ◽

Room Temperature Resistivity ◽

Undoped Material ◽

Donor And Acceptor ◽

And Diffusion

ABSTRACTThe study of doping of silicon nano-grains in semi-insulating polycrystalline silicon is of paramount importance since intense room-temperature luminescence at 1.54 µm has been demonstrated in this silicon-based semiconductor when doped with erbium ions. We have investigated the formation of p- and n-type layers of semi-insulating polycrystalline silicon by implantation and diffusion of B, P, As, and Er. The room-temperature resistivity can be changed by more than six orders of magnitude for both p- and n-type doping. A dramatic decrease of resistivity is observed for dopant concentrations above a threshold level; this effect is explained by assuming that the free-carrier motion is limited by grain boundary barriers and the electrical conduction is due to thermionic emission and tunneling of the carriers through the barriers. The prevalence of one mechanism over the other depends upon temperature, oxygen concentration and doping. In the undoped material the barrier height is large (≈ 0.5 eV), but for dopant concentrations above the threshold, it decreases with the doping level. Correspondingly, the conductivity increases by many orders of magnitude. The determination of the threshold value allows the evaluation of donor and acceptor grain boundary trap densities. Diodes have been fabricated by implantation and diffusion of boron and erbium. The I-V characteristics of these diodes are interpreted on the basis of the material modeling.

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Boron Diffusion in Polycrystalline Silicon

MRS Proceedings ◽

10.1557/proc-76-283 ◽

1986 ◽

Vol 76 ◽

Cited By ~ 1

Author(s):

Moustafa Y. Ghannam ◽

Robert W. Dutton ◽

Steven W. Novak

Keyword(s):

Grain Size ◽

Diffusion Coefficient ◽

Grain Boundary ◽

Grain Boundaries ◽

Polycrystalline Silicon ◽

Boundary Diffusion ◽

Crystalline Silicon ◽

Unit Area ◽

Grain Boundary Diffusion ◽

Boron Diffusion

ABSTRACTThe diffusion of boron in ion implanted LPCVD polycrystalline silicon is shown to be dominated by grain boundary diffusion at low and moderate concentrations. The diffusion coefficient is 2 to 3 orders of magnitude larger than its value in crystalline silicon. In preannealed polysilicon, the boron diffusion coefficient is found to be 30% smaller than in polysilicon annealed after implantation. This reflects the effect of the grain size in the diffusion coefficient since preannealed polysilicon has larger grains and smaller density of grain boundaries per unit area.

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Theoretical Calculation for the Young's Modulus of Poly-Si and a-Si Films

MRS Proceedings ◽

10.1557/proc-276-233 ◽

1992 ◽

Vol 276 ◽

Cited By ~ 2

Author(s):

Shuwen Guo ◽

Daowen Zou ◽

Weiyuan Wang

Keyword(s):

Experimental Data ◽

Thin Films ◽

Grain Size ◽

Grain Boundary ◽

Theoretical Calculation ◽

Young’S Modulus ◽

Young's Modulus ◽

Boundary Effects ◽

Wide Range ◽

Si Films

ABSTRACTA newly theoretical calculation for the Young's modulus Ey of poly-Si and a-Si thin films based on the combination of grain and grain boundary effects as well as the dependance of crystalline orientations is presented. The calculated results are in agreement with the experimental results in a wide range of grain size and hydrogen concentrations published in the literatures. The reason for aberration among experimental data of poly-Si and a-Si films caused by different hydrogen concentrations, texture and grain size has been discussed. The results offer a better understanding of. the effects of film structures on elastic properties of poly-Si and a-Si films.

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Structural Changes During Transient Post-Annealing of Preannealed and Arsenic Implanted Polycrystalline Silicon Films

MRS Proceedings ◽

10.1557/proc-52-145 ◽

1985 ◽

Vol 52 ◽

Author(s):

S. J. Krause ◽

S. R. Wilson ◽

R. B. Gregory ◽

W. M. Paulson ◽

J. A. Leavitt ◽

...

Keyword(s):

Grain Size ◽

Grain Boundary ◽

Sheet Resistance ◽

Network Structure ◽

Cellular Network ◽

Polycrystalline Silicon ◽

Structural Changes ◽

Silicon Films ◽

Post Annealing ◽

Polycrystalline Silicon Films

ABSTRACTPolycrystalline silicon films were transient preannealed, As implanted, and transient post-annealed at peak temperatures up to 1250°C for times up to 17.5 seconds. Structural changes occurring during post-annealing were examined by transmission electron microscopy. These results were correlated to Rutherford Backscattering and sheet resistance results. The grain size, which increased from 5–20 to 150–300 nm during preannealing, did not increase during post-annealing. During early stages of post-annealing, As diffused along grain boundaries and generated dislocation sources at grain boundary surfaces. Subsequently, as annealing progressed, a fine, As-rich cellular network structure propagated into the grains until the structure of an entire grain was transformed into a fine cellular network at the longest annealing times. Residual stresses in the film were relieved during formation of the network structure. The sheet resistance of preannealed samples, in comparison with non-preannealed samples with similar implantation and final transient anneals, was lower at shorter annealing times due to the larger grain size, which increased mobility, and the reduced grain boundary area, which trapped less As. It was also lower at longer annealing times due to the formation of the cellular network structure. In subsequent furnace stability tests for 30 minutes at 700–900°C, the sheet resistance increased less for preannealed than for non-preannealed samples.

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A New Approach to Temperature Dependent Ideality Factors in Schottky Contacts

MRS Proceedings ◽

10.1557/proc-260-359 ◽

1992 ◽

Vol 260 ◽

Cited By ~ 13

Author(s):

Zs. J. Horváth

Keyword(s):

Experimental Data ◽

Low Temperatures ◽

Schottky Diodes ◽

Thermionic Emission ◽

Schottky Contacts ◽

Temperature Dependent ◽

Model Calculations ◽

New Approach ◽

Barrier Heights ◽

Thermionic Field Emission

ABSTRACTSchottky diodes often exhibit anomalous current-vol tage characteristics at low temperatures (T) with T dependent ideality factors (IF) and apparent barrier heights (BH) evaluated for the thermionic emission. In this paper theoretical expressions are first presented for the T dependences of the IF and the apparent BH for the thermionic-field emission (TFE) including the bias dependence of BH. Model calculations are reported, which has been performed using these expressions, and their results are compared with the available experimental data. It is shown that the T dependence of the 1 Fs and apparent BHs often may be explained self consistently by the TFE with anomalously high characteristic energies Eoo.

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Percolative composite model for prediction of the properties of nanocrystalline materials

Journal of Materials Research ◽

10.1557/jmr.1997.0251 ◽

1997 ◽

Vol 12 (7) ◽

pp. 1828-1836 ◽

Cited By ~ 33

Author(s):

Rachman Chaim

Keyword(s):

Experimental Data ◽

Grain Size ◽

Grain Boundary ◽

Nanocrystalline Materials ◽

Composite Model ◽

Grain Sizes ◽

Percolation Thresholds ◽

Definition Of ◽

Critical Grain Size ◽

Transport Type

A physical percolating composite model is presented for description of the changes in the transport-type properties with grain size in nanocrystalline materials. The model is based on hierarchial percolation through the different microstructural components such as grain boundaries, triple lines, and quadruple nodes at grain sizes when their respective percolation thresholds are reached. The model yields critical grain sizes at which the properties may change significantly. These grain sizes depend on the grain boundary thickness. Master curves were calculated for the elastic modulus and compared to the experimental data from the literature. Better fit was found with the experimental data in comparison to Hill's approximation model. The critical grain size at grain boundary percolation threshold is suggested as a criterion for definition of materials to exhibit nanocrystalline properties.

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