Diamond-Based Schottky Barrier Diodes Show ‘Highest Breakdown Voltage’
Diamonds are an engineer's best friend? With a breakdown voltage of ~5 kV, diamond-based devices may hold the key to higher efficiency in power systems.
University of Illinois Urbana-Champaign (UIUC) researchers have developed a diamond-based diode with high breakdown voltage and low leakage currents. This device shows promise for the future of the grid as devices operate at higher voltages
The UIUC diamond-based Schottky barrier diodes show improved breakdown performance. Image used courtesy of UIUC
Although silicon continues to serve faithfully as a low-cost solution for low-power digital and analog circuits, it exhibits weaknesses compared to other semiconductors for high-power applications. In power electronics, where thermal performance is equally important, diamond-based devices prove to be highly efficient switching devices for the future of power transmission.
This article takes a closer look at the history of diamond-based semiconductors and provides more details on the UIUC device. In addition, we will discuss the implications of high-breakdown power electronic devices to give readers a sense of how diamonds may one day become an engineer’s best friend.
Boosting the Bandgap
Much like other materials such as silicon carbide (SiC) or gallium nitride (GaN), diamond exhibits a much wider bandgap than silicon, yielding better performance in power electronics applications. In addition, diamonds also include an extremely high breakdown field, enabling higher voltages and improved efficiency in power systems.
Compared to other semiconductors, diamond shows a higher reverse breakdown with a lower on-resistance, improving efficiency at higher powers. Image used courtesy of MDPI Materials
Researchers in recent years have focused heavily on fabricating diamond-based devices so that they can live up to their theoretical limits. Now the diamond diode from UIUC represents a critical step toward creating more diamond power electronics.
To fabricate their diamond-based Schottky barrier diodes (SBDs), the UIUC researchers used an MPCVD process with a high-pressure, high-temperature diamond substrate. They included an aluminum oxide (Al2O3) field plate, which improved the reverse breakdown performance. The final device’s breakdown voltage was 4,612 V, with a leakage current density of only 0.01 mA/mm.
The reverse breakdown performance of the diamond SDB with a field plate was 4,612 V. Image used courtesy of IEEE Electron Device Letters
Though many engineers may not need kV of reverse breakdown performance, diamond devices' low leakage and high reverse breakdown may ultimately perform very well in power electronics. For power transmission, where high voltages need to be stepped up and down, an efficient high-voltage semiconductor provides much more flexibility.
In addition to its electrical performance, diamonds also exhibit favorable thermal characteristics. The high thermal conductivity of diamond quickly moves any generated heat away, allowing devices to work better at higher powers compared to other semiconductors.
Diamond-based devices may improve efficiency for automotive, power transmission, and many more applications requiring high power or high voltage. This may ultimately reduce the carbon footprint of power systems.
The fabrication process for diamond-based SDBs could potentially be adapted to create diamond-based transistors. Image used courtesy of IEEE Electron Device Letters
While it may still be too early to say that diamond-based devices are the best solution for all power electronics, the developments made by UIUC researchers indicate a bright future for the semiconductor.