Scientists have found a way to augment the design of silicon carbide power devices that are used in electric vehicles and in other ones. This was stated in a recent study published in the journal Physical Status Solidi (b). Once released, this will create more effective and efficient engines.
The use of silicon carbide has problems like the Catch-22 between specific on-resistance, or a breakdown voltage, and specific resistance of the drift layer. It is widely used and hence it is important to reduce these issues. Researchers have come up with a super junction structure, which denotes the arrangement of the “n and p layers” inside trenches in the drift layer, which allows for the bipolar operation in such devices. And this opens a loophole to surpass the unipolar limit.
Another study in Japan revealed problems with SiC bipolar diodes created from Aluminum doping (Al doping). The ion implantation can create defects embedded deep in the semiconductor layers, which leads to negative effects on conductivity modulation. This affects the performance highly negatively.
“Our findings will help with the optimum design of SiC power devices, which will soon be employed in electric vehicles, trains, etc.,” said Associate Professor Masashi Kato of Nagoya Institute of Technology, Japan, who led the recent study, in a press release shared with IE via email. “These results will ultimately help improve the performance, as well as the size and energy consumption of traction systems in vehicles and trains.” Scientists formed two SiC PiN diodes using Al-doped p-layers to help better the performance.
One diode was made through epitaxial growth, and the other through ion implantation. Afterward, they evaluated the distribution of defects in both diodes with the help of conventional “deep level transient spectroscopy” (DLTS), which enabled them to investigate their properties with cathodoluminescence (CL). It was revealed that the p-type layer deposition via epitaxial growth left no additional damage in the adjacent n-type layers. However, it showed a minor instability that caused deep-level defects to form. Also, the specific on-resistance of this diode was low due to the above factor.
For the other diode, it was found out that it reached a high specific on-resistance without altering the conductivity modulation. The defects in the semiconductor device penetrated to at least 20 micro-meters (µm) from the area of implantation. “Our study shows that the ion implantation in SiC bipolar devices needs [s] to be processed at least 20 µm away from the active regions,” said Kato in the release shared with IE.
Low power consumption found in SiC power devices is the main factor that makes it an ideal option. This is important as climate change is getting worse, thanks in large part to the fossil fuel industry.