Silicon carbide yüksek gerilim aygıtları

The superior properties such as wide band gap, high breakdown electric field strength, high carrier mobility, and high thermal conductivity make Silicon Carbide (SiC) preferred over Silicon (Si) and Gallium Arsenide (GaAs), in high frequency, high temperature, and high voltage applications.SiC high voltage devices are preferred for their low reverse leakage current, low on-state voltage and resistance, high blocking voltage, and high performance at different temperatures. There are two types of the well-known SiC high voltage devices. One is Schottky diodes, which offer extremely high switching speed, but suffer from high leakage current. The other is, PiN diodes, which offer low leakage current, but show reverse recovery charge during switching and have a large junction forward voltage drop due to the wide band gap of SiC.In this work, various SiC Schottky and PiN epilayers with different doping concentrations between 1015 and 1016cm-3 and i-layer thicknesses between 6 and 20 ?m are used. First, taking the diode radius as 1 mm, resistance and capacitance values are calculated assuming the i-layer is fully depleted. The capacitance values are much less than 100pF and the resistance values are less than 100 m?. The capacitance value at a reverse bias of 50 volts is calculated with another approach, which is derived from the C-V graph of the diode, assuming the diode does not have to be fully-depleted at the given bias. The resulting capacitance is 106pF. At a reverse bias lower than the breakdown voltage, the minimum capacitance value cannot be reached. Knowledge of the capacitance value in a fully depleted thickness case reveals the breakdown voltage, which was found as -3030 volts for the Poland growth SiC PiN epilayer. In the second study, the Poland growth SiC PiN epilayer with a doping concentration of 8.4*1015 cm-3 was again used. With diode diameters ranging from 0.5 mm to 3 mm and depletion thicknesses ranging from 6 ?m to 100 ?m, the resistance and capacitance of the diode are calculated. The minimum resistance of 0.007? corresponds to the maximum capacitance of 1.05*10-10F, whereas the minimum capacitance of 1.75*10-13 F, corresponds to the maximum resistance of 4.4 ?. According to the resulting data sets, the optimal diode diameter and i-layer thickness for the desired resistance and capacitance values that is needed for the switching diode design can be selected.4H-SiC Schottky and PiN diodes with selected Ohmic, Schottky contacts and dielectric coating are fabricated. As the static characterization, we observe diodes with reverse breakdown voltages above 900 V, forward maximum current of 12.5A (current density up to 500 A/cm2), on-state diode resistance below 10 m?.cm2, and a capacitance value of 50 pF at a reverse bias of 40 volts. We also characterize the forward and reverse behaviors at different temperatures. As the dynamic characteristic, the rise-fall time is measured as 120 ns.Keywords: Silicon Carbide, Schottky diode, PiN diode, high breakdown electric field strength, Schottky contact, on-state voltage and resistance, capacitance, switching diode