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In this paper we present the current status of modelling the time evolution of the transient conductivity of photoexcited semi-insulating (SI) 4H-SiC taking into account the properties of defect centres. A comprehensive model that includes the presence of six, the most significant, point defects occurring in SI 4H-SiC crystals is presented. The defect centres are attributed to the two kinds of nitrogen-related shallow donors, a boron-related shallow acceptor, deep electron and hole traps, and the Z 1/2 recombination centre. We present the results of the state-of-the-art numerical simulations showing how the photoconductivity transients change in time and how these changes are affected by the properties of defect centres. The properties of defect centres assumed for modelling are compared with the results of experimental studies of deep-level defects in high purity (HP) SI 4H-SiC wafers performed by the high-resolution photoinduced transient spectroscopy (HRPITS). The simulated photoconductivity transients are also compared with the experimental photocurrent transients for the HP SI 4H-SiC wafers with different deep-level defects. It is shown that a high-temperature annealing producing the C-rich material enables the fast photocurrent transients to be achieved. The presented analysis can be useful for technology of SI 4H-SiC high-power photoconductive switches with suitable characteristics.

A model enabling the equilibrium conductivity and transient photoconductivity of semi-insulating 4H-SiC to be simulated has been demonstrated. Using this model, the simulations of both equilibrium conductivity and transient photoconductivity have been carried out. Both the simulation and experimental results have shown that the evolution of photoconductivity in time after switching on the band-to-band generation of electronhole pairs is strongly aected by the properties of deep level defects. The results of transient photocurrent measurements conrm the simulations results indicating that the Z 1/2 center is a very eective recombination center in semi--insulating 4H-SiC having detrimental eect on the transient photoconductivity.

In Poland, approx. 95% of electrical energy is generated in a coal combustion process. Saving electrical energy gives economic effects related to the smaller fees and contributes to protection of the natural environment. Additionally, saving electrical energy should translate into our health, lesser degradation of the natural environment, or less consumption of natural deposits of energy. The paper has presented the issues related to analysis of energy consumption in a selected building object. The analyse includes the following issues − document analysis related to the building’s power, energy distribution, and power consumption of individual load and time regimes of work of receivers in the object and analysis of electrical energy which has been measured in a building. Keywords: electricity quality parameters measurement, higher harmonics of current/voltage.

The procedure for determination of trap parameters by photo-induced transient spectroscopy is based on the Arrhenius plot that illustrates a thermal dependence of the emission rate. In this paper, we show that the Arrhenius plot obtained by the correlation method is shifted toward lower temperatures as compared to the one obtained with the inverse Laplace transformation. This shift is caused by the model adequacy error of the correlation method and introduces errors to a calculation procedure of defect center parameters. The effect is exemplified by comparing the results of the determination of trap parameters with both methods based on photocurrent transients for defect centers observed in tin-doped neutron-irradiated silicon crystals and in gallium arsenide grown with the Vertical Gradient Freeze method.