Thermal Limits of the Blocking Stability of Silicon Carbide Schottky Diodes

Abstract:
The blocking behaviour of Schottky diodes in silicon (Si) is known to be problematic at high voltage and high temperature operation: Due to the feedback loop of high leakage currents and self-heating a thermal runaway can easily occur. This problem was supposed to be solved by the use of silicon carbide (SiC) as semiconductor material because of the higher Schottky barrier. However, early SiC-Schottky diodes showed high leakage current densities and, therefore, were threatened by thermal runaway, too. In this work, the blocking stability of current SiC-Schottky diodes is investigated by means of stability calculations and measurements. Due to different leakage mechanisms in Schottky and pin diodes the leakage current has different voltage and temperature dependencies. The temperature difference DeltaTd, for which a doubling of the leakage current IR occurs, is significantly higher for SiC-Schottky diodes at nominal voltage than for Si-pin diodes. Thus, the thermal stability is achieved even under worst cooling conditions or during high temperature operation and thermal runaway during blocking is no longer a limiting factor.