ELECTROCRYSTALLIZATION OF SINGLE CRYSTAL BORON PHOSPHIDE SEMICONDUCTORS

BORON PHOSPHIDE (BP) IS A SEMICONDUCTOR WITH A WIDE BANDGAP AND EXCEPTIONAL PHYSICAL PROPERTIES, INCLUDING A MELTING POINT GREATER THAN 3,000 DEGREES CENTIGRADE, HIGH TEMPERATURE OXIDATION RESISTANCE, CHEMICAL STABILITY, HIGH THERMAL CONDUCTIVITY, AND EXTREME HARDNESS. THESE ATTRIBUTES MAKE IT ATTRACTIVE FOR USE IN HARSH ENVIRONMENTS. UNFORTUNATELY, THESE SAME PHYSICAL PROPERTIES MAKE IT DIFFICULT TO SYNTHESIZE BY CONVENTIONAL METHODS. THE OBJECTIVE OF THIS PROJECT IS TO SYNTHESIZE SINGLE CRYSTAL EPITAXIAL BP LAYERS ON SILICON SUBSTRATES USING ELECTROCRYSTALLIZATION. ELECTROCRYSTALLIZATION FROM MOLTEN SALT MELTS ALLOWS THE GROWTH OF SINGLE CRYSTAL LAYERS AT LOW TEMPERATURES (700-1000 DEGREES CENTIGRADE). BECAUSE THE CRYSTALLIZATION PROCESS IS DRIVEN ELECTRICALLY INSTEAD OF THERMALLY, EXTRAORDINARY FINE CONTROL CAN BE EXERCISED OVER THE DEPOSITION RATE AND COMPOSITION. ALSO, THE PROCESS CAN BE READILY SCALED UP TO PRODUCE LARGE WAFERS OR BOULES.