Materials research involving novel semiconductors for application to high-temperature electronics has taken on much interest recently by the scientific community. While silicon (Si) based electronic materials and devices continue to play a dominant role in much of the electrical power industry, novel high-power and high-temperature materials are of great interest to the electric combat systems community The technical interest in silicon carbide (SiC) is mainly due to its ability to operate at greatly elevated power and temperature (>300 degrees C) levels compared to its Si-based counterpart. High-power and temperature pulsed-power electronics can be exploited by future military combat systems, which could potentially provide significantly improved combat vehicle performance including increased lethality through extending the maximum obtainable gun performance using advanced electric weapon concepts such as electrothermal-chemical (ETC) and electromagnetic (EM) gun technologies. The results of recent experiments conducted at the U.S, Army Research Laboratory (ARL) and the University of Delaware demonstrate the electrical behavior of SiC and metal ohmic-contact layers as a function of thermal stress. It has been determined from these experiments that both titanium (Ti) and tantalum (Ta) metalization structures will provide a stable electrical ohmic-contact with n-type SiC at elevated temperatures for short bursts of time that are considered relevant for pulsed-powered electric weapon technologies. The Ti-SiC structure investigated exhibited a stable current-voltage (I-V) characteristic to as much as 800 degrees C for a 10-min burst, while Ta metalizations provided a stable I-V characteristic on SiC even after a temperature burst of 1,000 degrees C for as long as a 3-min interval. For samples of n-type, 4H SiC, metalized with (Ti), the standard deviation in resistance (resistivity) of the measured samples is less than 0.17 ohms for a sample having an average resistance of 4.45 ohms. The Ti-SiC sample was exposed to an elevated temperature range of 300-1,120 degrees C. For the Ta contact on SIG, the standard deviation in resistance is 0.05 ohms for a sample having an average resistance of 4.25 ohms over a temperature range of 600-1,120 degrees C. The experiments showed that for both Ti and Ta metalized SiC samples, the change in resistivity of annealed samples is between 3.8% and 1.2% compared to the average values of sample resistance based upon the I-V measurement technique used. These results indicate the ability of Ti-SiC and Ta-SiC structures to perform in a stable manner without significant electrical degradation to the metal contact, SIC substrate, or the metal-semiconductor interface as a function of high-temperature burst conditions.
