Density Of Grain Boundary States Research Articles

Hydrogen passivation of Fe-related deep energy levels at a direct silicon-bonded (1 1 0)/(1 0 0) grain boundary

The influence of hydrogenation on the electrical characteristics of an Fe-contaminated grain boundary (GB) formed by direct silicon bonding technology has been investigated. Due to hydrogen passivation, the density of GB states is reduced by one order of magnitude, but the energy distribution of deep levels and corresponding carrier capture cross-sections cannot be significantly affected. It is believed that the efficiency of hydrogen passivation is strongly dependent on the form of Fe contaminants at the GB.

Effect of iron contamination on grain boundary states at a direct silicon bonded (110)/(100) interface

AbstractThe effect of iron contamination on the electrical property of a (110)/(100) interfacial grain boundary (GB) in a p‐type direct‐silicon‐bonded wafer has been investigated by current–voltage and capacitance–voltage characteristics. It is found that iron contamination can change the charge property of this “model” GB. Based on proper physical modeling, it is found that compared to a “clean” grain boundary, iron contamination can significantly increase the density of GB states, and the corresponding GB neutral level has also been modified. These results show us a clear physical picture of Fe contamination influencing the GB states. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of nickel contamination on grain boundary states at a direct silicon bonded (1 1 0)/(1 0 0) interface

The effect of nickel contamination on the electrical characteristics of a (1 1 0)/(1 0 0) interfacial grain boundary in p-type direct silicon bonded wafers has been investigated by current/capacitance–voltage deconvolution. It was found that, compared with a clean grain boundary, nickel could increase the density of grain boundary states, and the corresponding hole capture cross-section was increased by one order of magnitude. Shockley–Read–Hall simulation verified that these nickel-related grain boundary states could cause a larger leakage current under reverse bias than that for a clean grain boundary.

Hydrogen passivation of deep energy levels at the interfacial grain boundary in (110)/(100) bonded silicon wafers

This letter evaluates the density of grain boundary (GB) states before and after hydrogenation by J-V, C-V, and capacitance transient methods using gold/direct silicon-bonded (DSB) (110) thin silicon top layer/(100) silicon substrate junctions. The GB potential energy barrier in thermal equilibrium was reduced by 70 meV from 0.46 eV (before hydrogenation) to 0.39 eV (after hydrogen treatment). Whereas the clean sample had a density of GB states of ∼6×1012 cm−2 eV−1 in the range of Ev+0.54–0.64 eV, hydrogenation reduced the density of GB states to ∼9×1011 cm−2 eV−1 in the range of Ev+0.56–0.61 eV, which is about a sevenfold reduction from that of the clean sample.

Impact of Cu contamination on the electrical properties of a direct silicon bonded (110)/(100) interfacial grain boundary

Cu contamination of a “model” grain boundary (GB) created by direct silicon bonding of (110)/(100) wafers has been investigated by monitoring the hole emission from GB states. It is found that the electronic states at the clean GB are localized, whereas following Cu contamination, they transform into bandlike states with much larger hole capture cross sections. Following an increase in Cu contamination at the GB by a quenching anneal, the density of GB states decreases, while the GB neutral level remains constant, essentially independent of contamination temperature. It is believed that the electrically active Cu-related states present at the GB are generated from the surfaces of localized Cu precipitates, whereas quench cooling from a higher contamination temperature produces a lower density of large precipitates which results in a reduced density of Cu-related GB states.

Atomic-scale model of the grain boundary potential in perovskite oxides

A combination of experiments and theoretical calculations is used to develop an atomic-scale model of the grain boundary potential in perovskite oxides. More specifically, pristine 8° and 58° [001] tilt grain boundaries in SrTiO 3 , which can be regarded as model systems for all cubic perovskite systems, are examined by Z-contrast imaging and electron-energy-loss spectroscopy. Based on results obtained from these systems, distance-valence least-square analysis and multiple-scattering calculations are used to determine the density of grain boundary states for the 8° and 58° grain boundaries, respectively. To compute the grain boundary potentials, the Thomas-Fermi approach of screened charges and the classical Schottky model is used. The validity of both models for various perovskite oxide grain boundary configurations is discussed, and the appropriate grain boundary potentials are compared with previously reported data.

Capacitance and conductance of Zn/sub x/Cd/sub 1-x/S/ZnTe heterojunctions

Capacitance-voltage and conductance-voltage characteristics of RF-sputtered ZnCdS films on ZnTe single crystals are studied as a function of frequency up to 1 MHz. It is found that the measured capacitance decreases with frequency while the conductance increases. A physical circuit model of the junction is proposed to explain this dependence. A relationship relating the junction capacitance to the polycrystalline film properties and the built-in voltage of the junction is derived. It shows that the junction capacitance is related to the average carrier concentration rather than the doping concentration of the polycrystalline material. From a C/sup -2/ versus V plot an average carrier concentration in the films which is in good agreement with that obtained by Hall measurement is obtained. The lower average electron concentration in the ZnCdS film near the substrate is due to either interdiffusion of Cd from the film into substrate or due to higher density of grain boundary states in the starting deposition portion of the film.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Grain boundary barrier heights and recombination velocities in polysilicon under optical illumination

A new model of recombination of carriers at grain boundaries in polycrystalline silicon under optical illumination is presented by considering the monoenergetic density of grain boundary states. Calculations have been performed on the grain boundary barrier heights ( V g), and on the interface and effective recombination velocities of minority carriers as a function of illumination level, grain size ( d) and bulk diffusion length of the minority carriers ( L b). These computations show that if the grain size lies in the range W g < d < L b (where W g is the depletion width) and the illumination level is high, the dependence of V g on grain size and illumination level will be much higher than that in the small and large grain size ranges. It is also found that, in the small grain size range, the dependence of interface and effective recombination velocities on the grain size is quite different, especially when illumination level is low. The dependence of the bending of the minority-carrier quasi-Fermi level in the grain boundary space-charge and quasi-neutral regions on the grain size and on the illumination level is studied. Calculations show that the validity of the quasi-equilibrium assumption decreases as grain size decreases and V g increases. This model predicts that the existing experimental studies cannot be used to calculate the effective recombination velocity of the minority carriers for polysilicon with small grain sizes. A number of experimental results have been fitted well on the basis of the theory.

Effect of dopants on the conductivity of electrodeposited CdTe

Thin-film polycrystalline CdTe was electrodeposited as described previously onto indium-tin-oxide coated glass under argon and then stored either under argon or air before and after the annealing step. Dopants were incorporated into films by several methods. Indium, Cadmium, and silver were introduced into the films either by codeposition or by electromigration techniques as described previously for copper, and the doping process was followed by heat treatment. Tellurium was introduced into two films by heating the samples in a tellurium atmosphere, and the effect of oxygen on the CdTe was investigated by a high-temperature heat treatment in air. The effect of these doping procedures on the conductivity was investigated at various temperatures. For this purpose, a system was built to measure extremely high resistances (&amp;gt;1012) over a large and well-controlled temperature range. Because of the polycrystalline nature of the films, the results are discussed in terms of a model in which the conducitivity is affected by the density of grain boundary states.

Electronic Properties of Grain Boundaries in GaAs: A Study of Oriented Bicrystals Prepared by Epitaxial Lateral Overgrowth

ABSTRACTThe electronic properties of tilt boundaries with misorientation angles ranging from 0 to 30° in n-type GaAs bicrystal layers have been investigated. The current-voltage and capacitance-voltage characteristics are consistent with a double-depletion-region model. The height of the grain boundary potential barrier remains constant while the density of grain boundary states varies with misorientation angle. Deep level transient spectroscopy has revealed the presence of two bands of grain boundary states at approximately 0.65 and 0.9 eV below the conduction band. These states are attributed to bond reconstruction at the grain boundary.