Abstract
The effect of generation rate on transient photoconductivity of semi-insulating (SI) 4H-SiC is discussed. The rate of generation of electron–hole pairs is dependent on the number of photons incident on the sample material and its absorption and reflection coefficients. The number of photons and their energy is dependent on the radiation power and wavelength of the light source illuminating the material. The results of research, obtained with a specialized simulator, present the influence of changes in the filling of individual defect centres’ levels on changes in conductivity of the test material observed after switching on the photoexcitation. For the purpose of simulations, presented is a versatile model of semiconductor material. It encompasses six point defects that appear in SI 4H-SiC materials the most often. Those defect centres correspond to Z1/2 recombination centre, deep electron and deep hole traps, nitrogen-related shallow donors of two kinds and a boron-related shallow acceptor. The simulation results can be used to design and determine properties of photoconductive switches.
Highlights
The effect of generation rate on transient photoconductivity of semi-insulating (SI) 4H-SiC is discussed
The method is intended for investigating defect structure of semiconductor materials and involves filling defect centres’ levels with excess electrons or holes generated during illumination of the test material with a pulse of light and measuring the transient waveform of photocurrent relaxation induced by thermal emission of charge carriers after turning the photoexcitation o ff[5,6]
We exploit a model described by a system of differential equations proposed in our earlier works[15–17], which is more complex as it enables us to simulate the kinetics phenomena in the presence of three types of defect centres, i.e. donorlike electron traps, acceptor-like hole traps and a donor-like recombination centre
Summary
The effect of generation rate on transient photoconductivity of semi-insulating (SI) 4H-SiC is discussed. Its wide band gap enables devices based one the semi-insulating silicon carbide to operate in a range of temperatures up to 600 °C Designing such devices requires an efficient method of investigation of the material electrical properties. The method is intended for investigating defect structure of semiconductor materials and involves filling defect centres’ levels with excess electrons or holes generated during illumination of the test material with a pulse of light and measuring the transient waveform of photocurrent relaxation induced by thermal emission of charge carriers after turning the photoexcitation o ff[5,6]. As the principle of operation of the photoconductive switches is based on the photoconductivity p henomenon[1], the PITS method is a very useful method for investigating the switches’ properties as well In this context, simulation studies of rates of changes in excess charge carrier concentrations are becoming very important for selection of measurement conditions that provide a proper quality of measured signals[7,8]. The knowledge is crucial in terms of designing the P CSSes[18] as the optical properties of the device’s material (induced by generation and recombination processes of charge carriers) determine its turn-on and turn-off times and its maximum switching frequency
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