This inventions' capacitor structure consists of Al2O3/AlN/4H-SiC material stack.
This inventions' capacitor structure consists of Al2O3/AlN/4H-SiC material stack. AlN and Al2O3 are ultrawide band gap materials, and as a result, they can be use as the dielectric in the capacitors. Their material properties are stable over wide temperature ranges (< 0 - ~ 600 ̊C). As a substrate, we have used 4H- SiC because of it has less than 1% lattice mismatch with AlN so that crystalline AlN can be grown. After that, polycrystalline or amorphous Al2O3 layer is deposited in order to reduce the leakage current of the capacitor at higher voltages. To finalize the capacitors, a nickel Schottky contact was deposited on Al2O3 and a nickel ohmic contact made on SiC. For the ohmic contact, Ni was annealed at 1000 ̊C for 1min. A schematic of two different proposed structures of the capacitors is shown below. This capacitor will provide high temperature stability without significant change in capacitance which is very important for the high temperature and high power applications. Most of the other state-of-the-art high temperature capacitors lose 70% or more of their capacitance at high temperatures, which is very risky for the whole system. But in our case, the capacitance changes less than 10% between -188 ̊C and + 327 ̊C, which is very effective for the circuit as well as for the system. Problem Addressed by Invention Wide-bandgap (WBG) power electronics will significantly increase the driving range and reduce the cost of electric vehicles, for example, through increasing the power conversion efficiency, switching frequencies, and power density, as well as supporting high temperature operations of traction drive systems. Future generations of high power electronic converters will rely on the flexibility and tolerance of components used to increase power density in order to supply a greater power in a smaller form. As a result of the increased power density, there will be an associated increase in heat load which generally degrades the performance of most board level components. Traditional capacitor design, with conventional dielectrics, cannot adequately meet all of the performance goals for capacitance density, weight, volume, and high temperature operation necessary for WBG power electronics. This invention is suitable for high temperature electronic applications with no significant change in capacitance.
* Capacitance doesn’t change over the approximate range -200C to 400C* Mid-to-high voltage application* Thin film capacitors with small volume* Can work without any costly and complicated cooling system* Will help to increase power density* Will help to reduce EMI and parasitic inductance and resistance
Concept has been proven through testing. Further tests and prototypes will be made in order to reduce leakage current further and make larger area capacitors.
* Electric vehicles
* Space exploration
* Down-hole exploration
* Other harsh environments