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

Horizon 2020 Project “Design for Resource and Energy efficiency in CerAMic Kilns- DREAM Project (Grant No: 723641), Horizon 2020 Industrial THERMal energy recovery conversion and management (Grant No:680599) and ESPRC (Grant No: EP/P004636/1)

https://bura.brunel.ac.uk/bitstream/2438/16137/3/Fulltext.pdf

Waste Heat Recovery Technologies and Applications

The density-matrix theory of semiconductor lasers with relaxation broadening model is finally established by introducing theoretical dipole moment into previously developed treatments. The dipole moment is given theoretically by the k . p method and is calculated for various semiconductor materials. As a result, gain and gain-suppression for a variety of crystals covering wide wavelength region are calculated. It is found that the linear gain is larger for longer wavelength lasers and that the gain-suppression is much larger for longer wavelength lasers, which results in that single-mode operation is more stable in long-wavelength lasers than in shorter-wavelength lasers, in good agreement with the experiments.

Density-matrix theory of semiconductor lasers with relaxation broadening model - Gain and gain-suppression in semiconductor lasers

We review the fundamental band gaps of wurtzite InN and group III nitride ternary alloys in the light of the recent discovery of the narrow band gap of InN. The results on the composition, temperature and hydrostatic pressure dependence of the band gaps of these alloys are summarized and discussed. The role of the Burstein–Moss shift for the accurate determination of the band gap is emphasized. The impact of the narrow band gap of InN on new device applications of group III nitrides is briefly discussed.

Band Gaps of InN and Group III Nitride Alloys

Device simulation of 17.3% efficient lead-free all-perovskite tandem solar cell

In this paper we investigate the optimized design of a short channel gate-all-around-junctionless (GAAJ) metal-oxidesemiconductor field-effect-transistor (MOSFET), including the source-drain extensions, by means of genetic algorithm solutions applied to a compact current-voltage analytical model. In fact, due to the complex device structure, it seems useful to exploit a metaheuristic-based approach to search the optimal combination of the fundamental geometrical and physical parameters that lead to an improved performance. Through this analysis, different parameter constraints are imposed for the calculation of specific objective functions. In particular, for a fixed gate-drain bias level, the task pursues the maximization of the drain current and cut-off frequency while limiting the short channel (SC) effects. The MOSFET series resistance is also evaluated in the transition region of the Id – Vgs characteristics which appear, however, strongly affected by SC effects. The accuracy of the model is verified by comparison with experimental data reported in literature.

Current-voltage analytical model and multiobjective optimization of design of a short channel gate-all-around-junctionless MOSFET

In this work different experimental current–voltage behaviours of several Al implanted 4H-SiC p–i–n diodes are investigated by means of numerical simulations in a wide range of currents and temperatures. Some devices for which recombination and tunneling are the dominant current processes at all biases are classified as “leaky” diodes. The well behaved diodes, instead, show good rectifying characteristics with a current conduction due to tunneling below 1.7 V, recombination between 1.7 V and 2.5 V, and diffusion processes above 2.5 V. At higher current regimes, a series resistance in excess of 1 mΩ cm 2 becomes the main current limiting factor. Depending on the relative weight between the contact resistances and the internal diode resistance, different temperature dependencies of the current are obtained. A good agreement between numerical and measured data is achieved employing temperature-dependent carrier lifetime and mobility as fitting parameters.

Analysis of different forward current–voltage behaviours of Al implanted 4H-SiC vertical p–i–n diodes

Numerical simulation study of a high efficient AlGaN-based ultraviolet photodetector

Full modelling is reported of the capacitance of a long PIN semiconductor diode with a high concentration of generation–recombination (g–r) centres and different concentrations of deep traps. There are considerable differences from the textbook results given for normal lifetime diodes which have low concentrations of g–r centres. For a low density of g–r centres, the capacitance is the usual value. That is it decreases as V −1/2 with increasing reverse bias while it increases rapidly with increasing forward bias. For high density of g–r centres and in reverse bias a departure from this voltage dependence is observed, while in forward bias a negative capacitance appears. This agrees with experiment. From these results we present a physical understanding of the processes involved. There are specific applications of these results to radiation damaged devices, lifetime killed diodes and devices made from high resistance and semi-insulating materials, especially in the interpretation of the C – V curves to evaluate the fixed space charge density.

Modelling of semiconductor diodes made of high defect concentration, irradiated, high resistivity and semi-insulating material: The capacitance–voltage characteristics

In this paper,. an accurate analytical model has been developed to optimize the performance of an Interdigitated Graphene Electrode/p-silicon carbide (IGE/p-4H-SiC) Metal semiconductor Metal (MSM) photodetector operating in a wide range of temperatures. The proposed model considers different carrier loss mechanisms and can reproduce the experimental results well. An overall assessment of the electrodes geometrical parameters’ influence on the device sensitivity and speed performances was executed. Our results confirm the excellent ability of the suggested Graphene electrode system to decrease the unwanted shadowing effect. A responsivity of 238 μA/W was obtained under 325-nm illumination compared to the 16.7 μA/W for the conventional Cr-Pd/p-SiC PD. A photocurrent to- dark-current ratio (PDCR) of 5.75 × 105 at 300 K and 270 at 500 K was distinguished. The response time was found to be around 14 μs at 300 K and 54.5 μs at 500 K. Furthermore, the developed model serves as a fitness function for the multi objective optimization (MOGA) approach. The optimized IGE/p-4H-SiC MSM-PD design not only exhibits higher performance in terms of PDCR (7.2 × 105), responsivity (430A/cm2) and detectivity (1.3 × 1014 Jones) but also balances the compromise between ultrasensitive and high-speed figures of merit with a response time of 4.7 μs. Therefore, the proposed methodology permits to realize ultra-sensitive, high-speed SiC optoelectronic devices for extremely high temperature applications.

Lakhdar Dehimi

Papers

Current-voltage analytical model and multiobjective optimization of design of a short channel gate-all-around-junctionless MOSFET

Analysis of different forward current–voltage behaviours of Al implanted 4H-SiC vertical p–i–n diodes

Numerical simulation study of a high efficient AlGaN-based ultraviolet photodetector

Modelling of semiconductor diodes made of high defect concentration, irradiated, high resistivity and semi-insulating material: The capacitance–voltage characteristics

An optimized Graphene/4H-SiC/Graphene MSM UV-photodetector operating in a wide range of temperature