Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Band parameters for III–V compound semiconductors and their alloys

Theoretical models of Schottky-barrier height formation are reviewed. A particular emphasis is placed on the examination of how these models agree with general physical principles. New concepts on the relationship between interface dipole and chemical bond formation are analyzed, and shown to offer a coherent explanation of a wide range of experimental data.

Recent advances in Schottky barrier concepts

The formation of the Schottky barrier height (SBH) is a complex problem because of the dependence of the SBH on the atomic structure of the metal-semiconductor (MS) interface. Existing models of the SBH are too simple to realistically treat the chemistry exhibited at MS interfaces. This article points out, through examination of available experimental and theoretical results, that a comprehensive, quantum-mechanics-based picture of SBH formation can already be constructed, although no simple equations can emerge, which are applicable for all MS interfaces. Important concepts and principles in physics and chemistry that govern the formation of the SBH are described in detail, from which the experimental and theoretical results for individual MS interfaces can be understood. Strategies used and results obtained from recent investigations to systematically modify the SBH are also examined from the perspective of the physical and chemical principles of the MS interface.

The physics and chemistry of the Schottky barrier height

Power semiconductor devices are key components in power conversion systems. Silicon carbide (SiC) has received increasing attention as a wide-bandgap semiconductor suitable for high-voltage and low-loss power devices. Through recent progress in the crystal growth and process technology of SiC, the production of medium-voltage (600?1700 V) SiC Schottky barrier diodes (SBDs) and power metal?oxide?semiconductor field-effect transistors (MOSFETs) has started. However, basic understanding of the material properties, defect electronics, and the reliability of SiC devices is still poor. In this review paper, the features and present status of SiC power devices are briefly described. Then, several important aspects of the material science and device physics of SiC, such as impurity doping, extended and point defects, and the impact of such defects on device performance and reliability, are reviewed. Fundamental issues regarding SiC SBDs and power MOSFETs are also discussed.

https://iopscience.iop.org/article/10.7567/JJAP.54.040103/pdf

Material science and device physics in SiC technology for high-voltage power devices

Forward density-voltage (J-V) measurements of titanium/4H-SiC Schottky rectifiers are presented in a large temperature range. While some of the devices present a behavior in accordance with the thermionic current theory, others present an excess forward current at low voltage level. This anomaly appears more or less depending on the rectifier and on the temperature. A model based on two parallel Schottky rectifiers with different barrier heights is presented. The characteristics show good agreement. It is shown that the excess current at low voltage can be explained by a lowering of the Schottky barrier in localized regions. A proposal for the physical origin of these low barrier height areas is given.

Barrier inhomogeneities and electrical characteristics of Ti/4H-SiC Schottky rectifiers

We investigate the initial oxidation and SiO2/6H-SiC interface formation by core level photoemission spectroscopy using synchrotron radiation. The results indicate that the direct oxidation of the 6H–SiC(0001)3×3 surface leads to SiO2 formation at low temperatures (500 °C) with a nonabrupt interface having significant amounts of mixed (Si–O–C) and intermediate (Si3+,Si2+,Si+) oxidation products. In contrast, C-free and a much more abrupt SiO2/6H-SiC(0001) interface formation is achieved when predeposited Si overlayer is thermally oxidized at low oxygen exposures and low temperatures (500 °C).

SiO2/6H-SiC(0001)3×3 initial interface formation by Si overlayer oxidation

Low pressure metalorganic chemical vapor epitaxial growth and characterization of high purity and Si‐doped indium phosphide on semi‐insulating (100) InP:Fe substrate are presented in this letter. Electrical characteristics of the layers were determined from Hall measurements. Hall mobilities as high as 145 000 cm2 V−1 s−1 at 77 K have been achieved on high purity layers with net donnor density ND−NA≂2×1014 cm−3. High resolution photoluminescence measurements were performed with the as‐grown layers at temperatures down to 1.7 K. Carrier concentration and the resulting mobility of intentionally Si‐doped low pressure metalorganic chemical vapor deposition grown InP layers were also studied.

Growth of ultrapure and Si‐doped InP by low pressure metalorganic chemical vapor deposition

Silicon carbide materials offer specific advantages to MESFET applications. However, to put them to good use requires to apply higher drain voltages than in GaAs devices. Therefore, in spite of the high thermal conductivity of the SiC substrates, this leads to a large power dissipation and a substantial increase in the local temperature. Depending on the device configuration, this self-heating can induce a negative differential conductance at very low frequency near dc regime. A simple analytical model is proposed, which yields a reasonable fit of the MESFET static characteristics. Further experimental evidence for such effects is also given, which corroborates the predictions of the model.

Christian Brylinski

Papers

Barrier inhomogeneities and electrical characteristics of Ti/4H-SiC Schottky rectifiers

SiO2/6H-SiC(0001)3×3 initial interface formation by Si overlayer oxidation

Growth of ultrapure and Si‐doped InP by low pressure metalorganic chemical vapor deposition

Self-heating effects in silicon carbide MESFETs

Power Density Comparison between Microwave Power MESFET's Processed on Conductive and Semi-Insulating Wafer