P-type Interface Research Articles

Ab initiostudy of the tensile strength and fracture of coincidence tilt boundaries in cubic SiC: Polar interfaces of the {122}Σ=9boundary

The tensile strength and fracture of polar interfaces of the {122} $\ensuremath{\Sigma}=9$ coincidence tilt grain boundary in cubic SiC have been examined through the behavior of electrons and ions using the ab initio pseudopotential method based on the local density-functional theory. The results are compared with previous results for the nonpolar interface of this boundary [M. Kohyama, Philos. Mag. Lett. 79, 659 (1999)], and the effects of interfacial configurations associated with Si-Si or C-C wrong bonds on the mechanical properties are discussed. In stable configurations of the N-type and P-type polar interfaces, all the interfacial bonds are well reconstructed similarly to the nonpolar interface, and the N-type and P-type interfaces contain C-C and Si-Si wrong bonds, respectively, although the nonpolar interface contains both kinds of wrong bonds. An ab initio tensile test has been applied to the supercell containing both types of polar interfaces, where uniaxial tensile strain normal to the interface is applied in small increments. Only the P-type interface is broken just after the maximum tensile stress of about 48 GPa and the N-type interface is not broken at all. This tensile strength of the P-type interface is larger than that of the nonpolar interface of about 42 GPa, and the N-type interface containing C-C bonds is the strongest. The tensile strength of all the reconstructed interfaces is rather large, and is over 80% of the theoretical and experimental strength of bulk SiC. A critical bond stretching of about 20% is observed for the Si-C bond breaking, similarly to the case of the nonpolar interface. It is shown that the atomic-scale inhomogeneity or singularity associated with the wrong bonds seriously affects the tensile strength and interfacial fracture. For the nonpolar interface, the fracture starts from the back Si-C bond of the C-C bond because of local stress concentration at the atomic scale, and proceeds from bond to bond rather continuously. For the P-type polar interface, on the other hand, there occurs no remarkable local stress concentration except for just before the fracture, because of the highly symmetric configuration. Thus larger tensile strain and stress are introduced before the fracture, and a larger number of interfacial bonds reach the criterion of bond breaking at the same time. This is the reason why the P-type polar interface containing Si-Si bonds is stronger than the nonpolar interface and is broken rather catastrophically. The present results should be applicable to general coincidence tilt grain boundaries in SiC with similar reconstructed configurations.

K-0102 第一原理計算による炭化ケイ素粒界の強度と破壊の研究(J01-1 第一原理強度解析)(J01 第一原理計算・分子動力学法による材料強度評価)

The tensile strength and fracture of the polar and non-polar interfaces of the {122}Σ=9 tilt boundary in cubic SiC have been examined through the behavior of electrons and atoms using the ab initio tensile tests. The strength of these interfaces is very large because of reconstructed interfacial bonds. However, the interfacial C-C and Si-Si bonds have serious effects. For the non-polar interface with both C-C and Si-Si bonds, the fracture starts at the back Si-C bond of the C-C bond because of local stress concentration, and the fracture proceeds rather continuously. The P-type polar interface with Si-Si bonds has larger tensile strength with no remarkable local stress concentration because of highly symmetric configuration, and the fracture occurs rather catastrophically. There exists the general critical bond stretching for the Si-C bond breaking.

Effects of wet oxidation/anneal on interface properties of thermally oxidized SiO/sub 2//SiC MOS system and MOSFET's

Effects of wet atmosphere during oxidation and anneal on thermally oxidized p-type and n-type MOS interface properties were systematically investigated for both 4H- and 6H-SiC. Deep interface states and fixed oxide charges were mainly discussed. The wet atmosphere was effective to reduce a negative flatband shift caused by deep donor-type interface states in p-type SiC MOS capacitors. Negative fixed charges, however, appeared near the interface during wet reoxidation anneal. In n-type SIC MOS capacitors, the flatband shift indicated a positive value when using wet atmosphere. The relation between interface properties and characteristics of n-channel planar 6H-SiC metal-oxide-semiconductor field effect transistors (MOSFETs) was also investigated. There was little relation between the interface properties of p-type MOS capacitors and the channel mobility of MOSFETs. The threshold voltage of MOSFETs processed by wet reoxidation anneal was higher than that of without reoxidation anneal. A clear relation between the threshold voltage and the channel mobility was observed in MOSFETs fabricated on the same substrate.

Electrical characterization of anodically grown native oxide on GaInSb

Surface passivation of single crystal bulk grown Ga 1− x In x Sb with x=0.08–0.18 is investigated using anodically grown native oxide and MOS devices. Electrical characterization of the interface is performed by using capacitance–voltage and conductance–voltage measurements at room temperature. The as-grown film shows relatively large hysteresis and high densities of negative (positive) fixed interface charges at the n- (p-) type interface. A long-time low-temperature annealing significantly improves interface properties, while a high temperature annealing degrades the interface. Very good interface properties are obtained for n-type wafers, with a fixed interface charge density of around mid 10 10 cm −2 (either positive or negative), an interface trap density in the range of low 10 11 to less than 1×10 10 cm −2 eV −1 and a small hysteresis induced by slow trap effect. In contrast, the p-type interface is always characterized by a high density of interface traps which leads to low-frequency-type C– V curves even at 1 MHz.

Gas source MBE growth of [formula omitted] device materials

This contribution reviews the status quo for the growth of Si SiGe device materials on Si(001) substrates by Si SiGe gas source MBE (GSMBE) technology. The technology is compared to related growth techniques like ultra-high vacuum chemical vapour deposition (UHV-CVD) and low pressure CVD (LP-CVD) in terms of equipment, process conditions and precursors used. Materials aspects like n- and p-type dopant behaviour, Ge incorporation and interface qualities are compared to those of the competing technologies. Realised devices based on GSMBE material such as heterostructure bipolar transistors (HBTs), (electro-)luminescent quantum well structures and modulation doped heterostructures for two-dimensional electron and hole gases are reviewed. Particular emphasis is given to devices that exploit selective area epitaxy (SAE). The limits of SAE in GSMBE are discussed. Devices employing SAE into small structures for the manufacture of e.g. semiconducting quantum point contacts are given. Summarising, we point to the particular strongholds of GSMBE within the device and materials research field; a field that demands versatility and flexibility but not necessarily high throughput. An outlook to the envisaged future role of GSMBE within research and production is given.

Fracture interface waves

Interface waves on a single fracture in an elastic solid are investigated theoretically and numerically using plane wave analysis and a boundary element method. The finite mechanical stiffness of a fracture is modeled as a displacement discontinuity. Analysis for inhomogeneous plane wave propagation along a fracture yields two dispersive equations for symmetric and antisymmetric interface waves. The basic form of these equations are similar to the classic Rayleigh equation for a surface wave on a half‐space, except that the displacements and velocities of the symmetric and antisymmetric fracture interface waves are each controlled by a normalized fracture stiffness. For low values of the normalized fracture stiffness, the symmetric and antisymmetric interface waves degenerate to the classic Rayleigh wave on a traction‐free surface. For large values of the normalized fracture stiffness, the antisymmetric and symmetric interface waves become a body S wave and a body P wave, respectively, which propagate parallel to the fracture. For intermediate values of the normalized fracture stiffness, both interface waves are dispersive. Numerical modeling performed using a boundary element method demonstrates that a line source generates a P‐type interface wave, in addition to the two Rayleigh‐type interface waves. The magnitude of the normalized fracture stiffness is observed to control the velocities of the interface waves and the partitioning of seismic energy among the various waves near the fracture.

Cyclic Voltammetric Studies of Charge Transfer Reactions at Highly Boron-Doped Polycrystalline Diamond Thin-Film Electrodes

Cyclic voltammetry and ac impedance analysis were used to measure the background current response and capacitance of interfaces formed at as grown (untreated) boron-doped polycrystalline diamond thin-film electrodes in contact with aqueous electrolytes. The diamond films (∼1 cm 2 , 15 μm thick ; carrier concentration, ∼10 17 cm -3 ) were grown on conducting Si substrates by plasma-enhanced chemical vapor deposition. Cyclic voltammetry was also used to determine the charge transfer reactions of several redox analytes at as grown and chemically wet etched diamond thin-film electrodes and to study the effect of surface pretreatment, including Fe(CN) 6 3-/4- , IrCl 6 2-/3- , Ru(NH 3 ) 6 3+/2+ , dopamine, 4-methylcatechol, MV 2+/+/0 , and ferrocene. The electrochemical response exhibited by the films is explained using two models : (i) traditional electron transfer at a p-type semiconductor-electrolyte interface and (ii) electron transfer at a composite electrode composed of nondiamond carbon impurities contained within a diamond matrix such that k° nondiamond >> k° diamond.

Metal contacts to GaAs with 1 eV Schottky barrier height

Metal Schottky barrier contacts to n-type (100) GaAs are described in which a 1 eV Schottky barrier height φB is achieved by using a very thin Si interface layer to influence the interface Fermi energy EiF. The metals investigated are Au, Cr, and Ti. The contact structure consists of a thick metal in combination with a ∼15–30 Å heavily p-type Si interface layer. The EiF and interface composition during initial contact formation were obtained by x-ray photoemission spectroscopy (XPS); the φB for the corresponding thick contacts was measured by current-voltage (I-V) and capacitance-voltage (C-V) techniques. The XPS, I-V, and C-V measurements gave consistent results. The 1 eV φB for the Si interface layer contact structure is independent of the contact metal.

A model for electron transfer at the illuminated p-type semiconductor-solution interface

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA model for electron transfer at the illuminated p-type semiconductor-solution interfaceShahed U. M. Khan and John O'M. BockrisCite this: J. Phys. Chem. 1984, 88, 12, 2504–2515Publication Date (Print):June 1, 1984Publication History Published online1 May 2002Published inissue 1 June 1984https://doi.org/10.1021/j150656a016RIGHTS & PERMISSIONSArticle Views307Altmetric-Citations31LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts