IONIZATION RATES AND CRITICAL FIELDS IN 4H SILICON-CARBIDE

Epitaxial p-n diodes in 4H SiC are fabricated showing a good uniformit y of avalanche multiplication and breakdown. Peripheral breakdown is o vercome using the positive angle beveling technique. Photo multiplicat ion measurements were performed to determine electron and hole ionizat ion rates. For the electric field parallel to the c-arris impact ioniz ation is strongly dominated by holes, A hole to electron ionization co efficient ratio of up to 50 is observed. It is attributed to the disco ntinuity of the conduction band of 4H SiC for the direction along the c axis, Theoretical values of critical fields and breakdown voltages i n 4H SiC are calculated using the ionization rates obtained. (C) 1997 American Institute of Physics.