Grain Boundaries In Semiconductors Research Articles

Theoretical investigation on the electronic states localized at grain boundaries in semiconductors

The electronic states localized at the silicon 〈0 0 1〉{1 3 0} tilt grain boundary were re-investigated by the first-principle calculation based on the density functional theory (DFT) for a starter of the theoretical research on a double Schottky barrier. We found that DFT predicts electrical activity of Hornstra’s model of this grain boundary in contrast with a previous tight binding approximation (TBA) calculation with Chadi’s parameterization predicting electrical inactivity of this grain boundary. It is shown that this disagreement is not brought about by the difference of the most relaxed structures between the TBA and DFT, but is the reflection of the wrong description of the conduction band in the TBA. It follows that previous knowledge on the anti-bonding grain boundary states obtained by TBA need to be verified through more reliable calculations.

Charge-transfer theory in polycrystalline semiconductors with deep impurity centers

This paper discusses the static and dynamic properties of charge transfer through electrically active grain boundaries in polycrystalline semiconductors with deep impurity centers in the bulk of the grains. The admittance of the grain boundary is computed as a function of frequency and applied dc bias Ub. When Ub≠0, the admittance is mainly controlled by charge-exchange processes of the intergrain boundary states and to an insignificant extent by the charge exchange of deep traps in the bulk of the semiconductor. The application of this theory to the spectroscopy of intergrain boundary states is considered.

Theoretical studies of grain boundaries in covalent materials

Atomic and electronic structures of grain boundaries in covalent materials such as semiconductors or covalent ceramics have been investigated using various theoretical methods. Significant advances have been made in the understanding of grain boundaries in elemental semiconductors. Currently, ab initio calculations for grain boundaries are possible by virtue of the development of the first-principles molecular dynamics method. A first ab initio approach to grain boundaries in SiC by using the models of the {122} Σ = 9 boundary is presented. It has been shown that interfacial C-C and Si-Si wrong bonds have significant effects on grain boundaries in SiC. The C-C and Si-Si bonds have bond lengths and bond charges similar to those in bulk diamond and Si, and the C-C bonds generate peculiar localized states at the valence-band edges.

Electrical Properties of Grain Boundaries in Ceramic Semiconductors

Electrical Properties of Grain Boundaries in Ceramic Semiconductors

Z-Contrast Imaging of Grain Boundaries in Semiconductors

Interest in grain boundaries in semiconductors is linked to the application of polycrystalline semiconductors as photovoltaic and interconnect materials. In real devices such as solar cells and MOS structures as well as future devices such as flat-panel displays, the intergranular regions of the polycrystalline solid have a significant effect on the flow of electronic current. These grain boundary barriers exist because the chemical potential of the boundary atoms are shifted from the bulk value by the change in local symmetry. The chemical potential is also changed by impurities, other structural defects, and other phases in the boundary. The lack of knowledge on the atomic structure of grain boundaries is, at present, the greatest barrier to advancements in the understanding of the electrical properties of these defects.The advances of the last few years have provided the tools with which to probe these interfaces at the true atomic scale. One such tool is the high-resolution scanning transmission electron microscope installed at Oak Ridge National Laboratory (VG Microscopes HB603) that can form a 1.27Å electron probe. Images are formed by scanning the probe across a thin sample and using an annular detector to collect electrons scattered to high angles. Because the annular detector collects electrons scattered over a wide range of angles, phase correlations and dynamical diffraction effects are averaged by this annular integration. Thus, an image with incoherent characteristics is produced and retained to relatively large specimen thickness.

電子材料の接合における界面問題 界面の電子構造計算 半導体の結晶粒界と金属／セラミックス界面

電子材料の接合における界面問題 界面の電子構造計算 半導体の結晶粒界と金属／セラミックス界面

Theoretical Study of the Atomic and Electronic Structures of Grain Boundaries in Semiconductors

Theoretical Study of the Atomic and Electronic Structures of Grain Boundaries in Semiconductors

High Temperature Atomic Simulations of Grain Boundaries in Semiconductors Using a New Type of Periodic Boundary Conditions

High Temperature Atomic Simulations of Grain Boundaries in Semiconductors Using a New Type of Periodic Boundary Conditions

Current–voltage characteristics of grain boundaries in cast polycrystalline silicon

Current-voltage ( I - U ) characteristics of grain boundaries (GBs) in cast polycrystalline silicon are reported. It is found experimentally that these I - U characteristics show a dependence on the polarity of the applied voltage. A model is developed to understand the I-U characteristics of GBs in semiconductors, taking into account the observed difference in doping concentration in the grains forming the GB. A single trap energy level is assumed for GB interface states. The potential barriers at GBs are estimated by calculating the increase in the density of filled interface states at the GB due to the applied bias. The I-U characteristics calculated through this model show the same general features as those of measured I-U characteristics.

Theoretical Study of Grain Boundaries in Compound Semiconductors. Analysis of Coincidence Tilt Boundaries in SiC.

The interface stoichiometry and the wrong bonds between like atoms are important subjects of consideration in the study of grain boundary properties of compound semiconductors. The polar and non-polar interfaces are defined from the interface stoichiometry. A general definition of the interface stoichiometry has been presented. The atomic and electronic structures of one type of coincidence tilt boundary in S1C, the {211} σ=3 boundary, have been calculated on the base of the reconstructed models by using the self-consistent tight-binding method. These have been compared with the previous results of the {122} σ=9 boundary in SiC. It has been shown that the wrong bonds make the boundary energy fairly high by the repulsive electrostatic energies and generate localized states at the band edges. It has been also shown that the different bond lengths of the wrong bonds affect the local bond distortions to a great extent at the interfaces, which determines the relative stability between the present models. The stability of the wrong bonds in the interfaces of general heterovalent compound semiconductors has been also discussed.

Micro- to nano-characterization of semiconductor grain boundaries

This paper examines the use of surface-analysis methods in the characterization of grain boundaries in semiconductors. The purpose is to demonstrate the utility of increasing spatial resolution in the evaluation of defects. Three distinct mechanisms for adjusting the electronic properties of defect regions of semiconductors are presented. These include the passivation of grain boundaries by chemical methods; the electrical neutralization of shallow acceptor impurities; and, the doping of the defect regions. Secondary ion mass spectrometry, Auger electron spectroscopy and specialized scanning tunneling microscopy are used to evaluate the grain-boundary structure, composition and chemistry. Complementary macro- and nano-electro-optical characterization techniques based on electron-beam-induced current and photoluminescence provide correlated information on the effects of the chemical-treatment methods.

Influence of the Dissociation into Shockley Partials on the Dislocation Transmission across [011] Tilt Grain Boundaries in Elemental Semiconductors

Influence of the Dissociation into Shockley Partials on the Dislocation Transmission across [011] Tilt Grain Boundaries in Elemental Semiconductors

Theoretical Study of the Polar and Non-Polar Interfaces of Grain Boundaries in Compound Semiconductors

Theoretical Study of the Polar and Non-Polar Interfaces of Grain Boundaries in Compound Semiconductors

Theoretical Study of Polar and Non-Polar Interfaces in Compound Semiconductors: A Thermodynamic Analysis Based on Electronic Structure Calculations

AbstractPolar and non-polar interfaces of grain boundaries in compound semiconductors can be defined by the stoichlometry in the interface region, and It Is possible to construct two polar and one non-polar Interfaces for a symmetrical tilt grain boundary In the zinc-blende structure of which the Interface Is polar surfaces. The atomic and electronic structures of polar and non-polar interfaces of the {122} Σ=9 grain boundary in SIC have been examined by using the SCTB method coupled with the supercell technique. By using the calculated binding energies, the relative stability of the polar and non-polar interfaces has been analyzed through calculations of the thermodynamic potentials as a function of the atomic chemical potentials. It has been shown that the wrong bonds and the stoichlometry much Influence the stability and properties of grain boundaries in SiC. The stability of polar Interfaces In heterovalent compound semiconductors has been discussed.

Hydrogen at semiconductor grain boundaries and interfaces

This paper is a review of the known effects of hydrogen in crystalline semiconductor grain-boundaries and interfaces and of the recent progress in the fundamental study of the mechanisms of hydrogen-interfaces interactions. The interfaces considered are: grain boundaries of polycrystalline semiconductors, semiconductor/semiconductor or semiconductor/metal interfaces, silicon/silicon oxide interfaces (including precipitated silicon oxide interfaces), and semiconductor/electrolyte interfaces. The influence of structural and electronic defects on the hydrogen passivation processes is discussed. Emphasis is laid upon the role of segregated impurities on the electrical activity of interfaces and its subsequent passivation by hydrogen. Some ideas are given for development of experimental and theoretical research to improve the understanding of the mechanisms of hydrogen action.

Determination of grain-boundary defect-state densities from transport measurements

Transport of majority carriers across the potential barriers frequently found at grain boundaries in semiconductors is treated by considering sequential drift diffusion and thermionic emission processes. The regimes where the thermionic or drift-diffusion approximations can reasonably be made are readily determined from the analysis. Over a wide doping range, we find boundary transport to be under mixed control. Numerical calculations are made for a given barrier height with a range of bulk doping levels. A deconvolution scheme to determine defect-state densities is given and tested for a variety of densities of states.

Σ =13 tilt grain boundary in silicon bicrystal

The structure of grain boundaries (GBs) in metals, semiconductors and ceramics is of considerable interest because of their influence on physical properties. Progress in understanding the structure of grain boundaries at the atomic level has been made by high resolution electron microscopy (HREM) . In the present study, a Σ=13, (510) <001>-tilt grain boundary in silicon was characterized by HREM in conjunction with digital image processing and computer image simulation techniques.The bicrystals were grown from the melt by the Czochralski method, using preoriented seeds. Specimens for TEM observations were cut from the bicrystals perpendicular to the common rotation axis of pure tilt grain boundary, and were mechanically dimpled and then ion-milled to electron transparency. The degree of misorientation between the common <001> axis of the bicrystal was measured by CBED in a Philips EM 400ST/FEG: it was found to be less than 1 mrad. HREM was performed at 200 kV in an ISI-002B and at 400 kv in a JEM-4000EX.

Intrinsic instability and entropy stabilization of grain boundaries.

A simple method is proposed to describe the thermodynamic properties of disordered grain boundaries in nanocrystalline metals and semiconductors. Based on a free-volume approach at negative pressure of the universal equation of state, the maximum free volume, thermal expansion coefficient, specific-heat capacity, and excess enthalpy, entropy, and free energy of grain boundaries are derived from well-known thermodynamic relationships. The results show good agreement with available experimental data and suggest an intrinsic mechanical instability of a nanograin boundary (Gibbs instability) accompanied by divergences of \ensuremath{\alpha} and ${\mathit{c}}_{\mathit{p}}$, and the possibility of an entropy stabilization of nanograin boundaries.

Grain boundary observation in polycrystalline CdSe by photoelectrochemical etching techniques

A new method for studying grain boundaries of polycrystalline CdSe semiconductors by the use of photoelectrochemical etching (photoetching) has been described. The selectivity of the photoetching site of CdSe depends on the grain structure, for instance on the presence of grain boundaries or on crystallographic orientation of the grain bulk. After the photoetching treatment of CdSe under weak anodic polarization, the grain boundaries are left undissolved. This finding makes it possible to observe directly the grain boundaries as separated from the grain bulk. A transmission electron micrograph and a selected area diffraction pattern of the grain boundary are shown.

Atomic and Electronic Structures of Grain Boundaries in Semiconductors

Atomic and Electronic Structures of Grain Boundaries in Semiconductors