DEVELOPMENT OF SILICON CARBIDE METAL-SEMICONDUCTOR FIELD-EFFECT TRANSISTORS FOR HIGH POWER OPERATION AT HIGH TEMPERATURES

SILICON CARBIDE POSSESSES A UNIQUE COMBINATION OF PROPERTIES THAT ALLOW SIMULTANEOUS HIGH TEMPERATURE AND HIGH POWER OPERATION OF ELECTRONIC DEVICES MADE FROM THIS MATERIAL. THE CUBIC FORM OF SIC (BETA) HAS A WIDE BANDGAP (2.2 EV @ 27 DEG C), WHICH THEORETICALLY GIVES A MAXIMUM OPERABLE TEMPERATURE OF 925 DEG C. ALPHA SIC (6H) HAS AN EVEN WIDER BANDGAP OF 2.86 EV @ 27 DEG C, GIVING A MAXIMUM OPERABLE TEMPERATURE OF 1240 DEG C. BOTH FORMS ALSO HAVE A HIGH BREAKSOWN ELECTRIC FIELD OF 4X10(6) V/CM (10 TIMES THAT OF SI & GAAS),WHICH ALLOWS HIGH POWER OPERATION. RECENT RESEARCH ON SIC HAS RESULTED IN THE FABRICATION OF MESFETS AND MOSFETS THAT, FOR THE FIRST TIME, SHOW OPERATION AT HIGH TEMPERATURES. WHILE THE MOSFETS HAD VERY GOOD CURRENT-VOLTAGE CHARACTERISTICS UP TO 650 DEG C, THE MESFET OPERATION WAS LIMITED TO 350 DEG C BECAUSE OF REACTION OF THE GOLD SCHOTTKY CONTACT WITH THE SIC, AND BY THE LOWER QUALITY MATERIAL (BETA-SIC ON SI SUBSTRATES) USED FOR THESE SCHOTTKY BARRIED DEVICES. HOWEVER, RECENT RESEARCH HAS ALSO YIELDED MUCH BETTER SCHOTTKY CONTACTS FOR HIGH TEMPERATURE (PLATINUM OR PLATINUM SILICIDE) AND PROCESSES FOR GROWING BOTH BETA-SIC AND 6H-SIC THIN FILMS THAT HAVE MUCH LOWER DEFECT DENSITY THAN THAT MENTIONED PREVIOUSLY. IT IS HEREIN PROPOSED TO FABRICATE MESFETS IN THE HIGHER QUALITY SIC THIN FILMS (BOTH BETA AND 6H) USING PLATINUM BASED SCHOTTKY CONTACTS IN ORDER TO DECREASE THE ...THRESHOLD LEAKAGE CURRENT AND INCREASE THE MAXIMUM OPERABLE TEMPERATURE OF THESE DEVICES.