Evaluation of Electrical Resistivity Characteristics of Metalized 4H-SiC for Application to Electric Guns

Report No. ARL-TR-1937
Authors: Katulka, Gary L.
Date/Pages: April 1999; 30 pages
Abstract: The experiments described 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 after exposure to 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 deg 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 deg 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. For the Ta contact on SiC, the standard deviation in resistance is 0.05 ohms for a sample having an average resistance of 4.25 ohms. 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.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 1999