Silicon carbide diodes came out in 1985. Yoshida made it on 3C-silicon carbide. Its Schottky barrier height is 1.15 (0.15) eV measured by capacitance and 1.11 (0.03) eV measured by optical response. Its breakdown voltage is only 8 volts. The breakdown voltage of the first 6H-silicon carbide Schottky diode was approximately 200 volts. Bhatnagar reported the first high-voltage 400V 6H-SiC Schottky barrier diode with low on-state voltage drop (1 V) and no reverse recovery current. With the continuous improvement of silicon carbide single crystal, epitaxial quality and technical level, more and more silicon carbide diodes with superior performance have been reported.
In 1993, the first silicon carbide diode with a breakdown voltage exceeding 1000 volts was reported. The Schottky contact metal of the device is palladium. It uses nitrogen type epitaxy, doping concentration is 110 cm, thickness is 10 microns. Around 1995, high-quality 4H-silicon carbide single crystals appeared. It has higher electron mobility and greater critical breakdown electric field than 6H-silicon carbide, which makes people more inclined to study 4H-silicon carbide Schottky diodes.
Nickel/4H-silicon carbide diode was first reported in 1995. The epitaxial doping concentration is 11016 cm, the thickness is 10 microns, the breakdown voltage is 1000 V, the forward voltage drop is 1.06 V at 100 A/cm, and the specific on-resistance at room temperature is 210 cm. In 2005, Yuki Nakamura and others used molybdenum as a Schottky contact with a breakdown voltage of 4.15 kV and a specific contact resistance of 9.07 mcm. The barrier height of Schottky diodes also increases as the annealing temperature increases. When the annealing temperature is 600, the barrier height is 1.21 eV, and the ideality factor is stable, and does not change much as the annealing temperature increases. Zhao Jianhui used nitrogen-type silicon carbide epitaxy and multi-stage junction extension technology to fabricate a nickel/4H-silicon carbide Schottky diode with a breakdown voltage of 10.8 kV. The epitaxial doping concentration is 5.610cm and the thickness is 115m. Schottky diodes use multi-stage junction termination extension technology to protect the edge of the Schottky junction from premature breakdown.
Silicon carbide diode has no additional carrier injection and storage during the turn-on process, so the reverse recovery current is small, the turn-off process is fast, and the switching loss is small. Traditional silicon Schottky diodes can only be used in low voltage applications of 120-200 volts, and are not suitable for working above 150, because the work function difference between all metals and silicon is not very large, and the Schottky barrier of silicon is low, and silicon SBD The reverse leakage current is large and the blocking voltage is low. However, silicon carbide SBD makes up for the shortage of silicon SBD. Many metals, such as nickel, gold, palladium, titanium, cobalt, etc. It can form Schottky contacts with silicon carbide whose Schottky barrier height exceeds 1 eV. According to reports, the barrier height of gold/4H-silicon carbide contact can reach 1.73 eV, while the barrier height of titanium/4H-silicon carbide contact is relatively low, but the highest can reach 1.1 eV. The Schottky barrier height between 6H-SiC and various metal contacts varies greatly, with a minimum value of 0.5 eV and a maximum value of 1.7 eV. Therefore, SBD has become the first focus of the development of silicon carbide power electronic devices. It is an ideal device that integrates high voltage, high speed, low power consumption and high temperature resistance. At present, a variety of silicon carbide devices with a high degree of success have been developed in the world.
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