The application of Silicon Carbide (SiC) power semiconductors is accelerating, from electric vehicles to solar photovoltaics. But where does this material come from? What's so special about it? Why did Silicon Carbide, used as the basis for radio detectors over a century ago, take so long for the semiconductor industry to develop?
In the early 20th century, experimenters discovered that crystals of various materials, such as germanium, could produce an "asymmetric current flow," or rectification, a phenomenon that was applied to crystal radios. When attempting to use Silicon Carbide, unusual behavior occurred. The crystals emitted yellow light, sometimes green, orange, and blue. Transistors were discovered 40 years ago.
Although SiC was quickly replaced as a light-emitting diode (LED) by gallium arsenide and gallium nitride, which offer 10-100 times higher luminous efficiency, it continues to attract attention in the electronics field as a material. Its thermal conductivity is 3.5 times that of silicon, and heavy doping can achieve even higher conductivity while maintaining high electric field breakdown. Mechanically, it is very rigid and inert, with an extremely low coefficient of thermal expansion and a high temperature rating. SiC does not fuse—it sublimates at around 2700°C.
In its early days, Silicon Carbide was considered the ideal semiconductor device. What obstacles hindered its development compared to silicon? The main defects present in SiC crystals were eliminated: edge dislocations, various types of screw dislocations, triangular defects, and basal plane dislocations. The smaller the crystal, the worse its anti-resistance, making these components essentially unusable.
There were also issues with using SiC and SiO2 interconnects to create popular MOSFET and IGBT devices. However, with technological advancements, quality continued to improve, and 6-inch wafers now offer acceptable quality. A breakthrough (also known as nitridation or nitride oxide annealing) allowed the stable growth of SiC on SiC.
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