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

Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (e) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.

A review of Ga2O3 materials, processing, and devices

J. Y. Tsao,* S. Chowdhury, M. A. Hollis,* D. Jena, N. M. Johnson, K. A. Jones, R. J. Kaplar,* S. Rajan, C. G. Van de Walle, E. Bellotti, C. L. Chua, R. Collazo, M. E. Coltrin, J. A. Cooper, K. R. Evans, S. Graham, T. A. Grotjohn, E. R. Heller, M. Higashiwaki, M. S. Islam, P. W. Juodawlkis, M. A. Khan, A. D. Koehler, J. H. Leach, U. K. Mishra, R. J. Nemanich, R. C. N. Pilawa-Podgurski, J. B. Shealy, Z. Sitar, M. J. Tadjer, A. F. Witulski, M. Wraback, and J. A. Simmons

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Ultrawide-Bandgap Semiconductors: Research Opportunities and Challenges

By systematically comparing experimental and theoretical transport properties, we identify the polar optical phonon scattering as the dominant mechanism limiting electron mobility in β–Ga2O3 to <200 cm2/V s at 300 K for donor doping densities lower than ∼1018 cm–3. Despite similar electron effective mass of β–Ga2O3 to GaN, the electron mobility is ∼10× lower because of a massive Frohlich interaction, due to the low phonon energies stemming from the crystal structure and strong bond ionicity. Based on the theoretical and experimental analysis, we provide an empirical expression for electron mobility in β–Ga2O3 that should help calibrate its potential in high performance device design and applications.

Intrinsic electron mobility limits in β-Ga2O3

Electron density and Hall mobility data were simultaneously analyzed in the frame of the relaxation time approximation in order to identify the main scattering mechanisms that limit the carrier mobility in β-Ga2O3 single crystals. The Hall factor correction was self-consistently included in the fitting procedure. The analysis indicates that low-energy optical phonons provide the main scattering mechanism, via lattice deformation. In this regard, a deformation potential of about 4 × 109 eV cm−1 was estimated. Furthermore, it is shown that the Hall coefficient and mobility can be measured by the usual experimental geometry, and the standard transport theory can be applied when off-diagonal elements of the resistivity tensor at zero magnetic field are negligible with respect to the diagonal ones. This directly follows from the analysis of the magneto-resistive tensor of a semiconductor with monoclinic structure. Such a requirement is satisfied under the hypothesis of nearly spherical energy surfaces, as has been reported to occur at the Γ minimum of the conduction band of β-Ga2O3.

https://iopscience.iop.org/article/10.1088/0268-1242/31/3/035023/pdf

Analysis of the scattering mechanisms controlling electron mobility in β-Ga2O3 crystals

Thermal stability of ε-Ga2O3 polymorph

Low resistivity n-type e-Ga2O3 epilayers were obtained for the first time either by adding silane to the gas phase during the metal organic vapour phase epitaxy deposition or by diffusing Sn in nominally undoped layers after the growth. The highest doping concentrations were few 1018 cm−3 and about 1017 cm−3 for Si and Sn doping, with corresponding resistivity below 1 and 10 Ω cm, respectively. Temperature dependent transport investigation in the range of 10-600 K shows a resistivity behavior consistent with the Mott law, suggesting that conduction through localized states dominates the electrical properties of Si- and Sn-doped samples. For both types of dopants, two different mechanisms of conduction through impurity band states seem to be present, each of them determining the transport behavior at the lower and higher temperatures of the measurement range.

/pdf/si-and-sn-doping-of-e-ga2o3-layers-2qk007amwm.pdf

Si and Sn doping of ε-Ga2O3 layers

The temperature dependence of the Hall hole density and the Hall mobility data of heavy doped p-type 4H-SiC(Al) materials obtained by Al+ ion implantation have been analysed in the frame of the charge neutrality condition and the relaxation time approximation. Samples with implanted Al concentrations in the range 1019–1020 cm−3 and 1950 °C/5 min conventional annealing have been taken into account. The reliability of the calculation has been critically discussed by focusing the attention on both the validity limits of the models for the impurity scattering mechanisms and the adopted Hall factor. By introducing empirical mass anisotropy factors, reasons were given in favour of a generalized use of the unique experimental evaluation of the Hall factor reported by the literature for p-type 4H-SiC, assessed for an Al acceptor density in the range of 1.8 × 1015 cm−3–2 × 1018 cm−3. The simultaneous fits of the Hall hole density and mobility data indicate an electrical activation of the Al impurities of the order or higher than 70% and a compensation of about 10% of the Al acceptors.

Analysis of the hole transport through valence band states in heavy Al doped 4H-SiC by ion implantation

The fundamental absorption of GaSb, experimentally investigated by optical transmission measurements performed in the temperature range 9--300 K on nominally undoped molecular-beam-epitaxy-grown GaSb layers, is compared to theory. Calculations related to a band-to-band optical transition theory based on the models of Kane and Elliott, considering the band nonparabolicity and the electron-hole (exciton) interaction effects, respectively, show excellent agreement with experimental results. The role of different contributions to absorption coefficient is discussed.

Antonella Parisini

Papers

Analysis of the scattering mechanisms controlling electron mobility in β-Ga2O3 crystals

Thermal stability of ε-Ga2O3 polymorph

Si and Sn doping of ε-Ga2O3 layers

Analysis of the hole transport through valence band states in heavy Al doped 4H-SiC by ion implantation

Optical absorption near the fundamental absorption edge in GaSb