Enhanced capabilities of Silicon Carbide (SiC) power semiconductor technology permit new ultra-high voltage and current applications and offer attractive options for power electronics in satellites, space stations and space exploration. However, the space environment has multiple radiation sources that interact with the SiC crystal and can damage the circuit. Studies show that when heavy ions impinge on an operating SiC power device, the device degradation may range from no discernable damage to increased leakage to catastrophic failure. In SiC MOSFET devices subjected to high-energy ion bombardment in the OFF-state, single-event burnout (SEB) and single-event gate rupture (SEGR) are two major failure types. Commercial SiC power devices have been observed to incur catastrophic failure at biases below 40% of their nominal blocking voltage, and irreversible degradation (SEGR) at biases well below 10% when exposed to ions with a Linear Energy Transfer (LETs) at 10 MeV-cm2/mg. Latent gate damage that precedes SEGR significantly limits the safe operation area of SiC MOSFETs for space applications. To avoid SEB failures, derating schemes are proposed like reducing the operating voltage to less than half its rated value. Similarly, to minimize SEGR, the operating voltage is reduced to less than one quarter of its rated value. Such de-rating penalty not only diminishes the SiC technology advantages of performance, cost and weight in space but may lead to costly field failures. SCDevice is developing a patented self-aligned device design for high-voltage SiC MOSFETs, with the goal of achieving reliable gate oxide performance up to 600V (state of the art MOSFET survives about 100V) for ion striking with LET=40 MeV-cm2/mg. Goal of Phase-I is to (a) Optimize device design for performance and (b) Demonstrate electric field across gate oxide below 4MV/cm for the ion strike at bias of 600V in the off-state.
Radiation-tolerant SiC MOSFET devices could have significant impact on satellite launch costs due to reduced weight of overall sub-systems, smaller satellites, or satellites with greater useful functionalities for a given weight and volume.
Example use in Space Electric Propulsion: When utilized in place of Si MOSFET in satellite electric propulsion power supply, SiC MOSFETs have been shown to improve power efficiency of Hall thruster Power Processing Units (PPU) from 94% to 97% and Ion thrusters from 92% to 95.8%
The burgeoning private satellite industry in the United States will be the single most promising market for SCDevice's radiation-tolerant SiC MOSFET. Satellites, aerospace and automotive applications will greatly benifit from (a) low-loss switching of SCDevice's MOSFET due to low gate-drain capacitance compared to commercial MOSFET and (b) Low drain-source leakage for high temperature applications