Growth Studies of Silicon Carbide Crystals

Silicon carbide crystals are commonly grown from the vapor at a temperature of about 2600°C in so called "sublimation" furnaces wherein crystals are grown on the inside walls of a cavity formed within a large porous block of silicon carbide. A model for growth in this system is postulated and growth rate as a function of temperature is calculated. Growth in argon with pulses of nitrogen introduced at regular (7½ min) intervals is shown to produce sharp green lines that define the successive crystal sizes during the entire growth period (~8 hr). Temperature changes are made during growth and the growth rates are measured during successive temperature cycles. Considerable fluctuation in growth rate is revealed by this new measuring procedure. Theory and experiment are in qualitative agreement.