Evaluation of on-state resistance and boron-related levels in n-type 4H-SiC

Specific on-resistance R-on. estimated from current density-voltage characteristics of Schottky diodes on thick layers exhibits variations from tens of m Omega.cm(2) to tens of Omega.cm(2) for different doping levels. In order to understand the occurrence of high on-state resistance, Schottky barrier heights were first estimated for both forward and reverse bias with the application of thermionic emission theory and were in agreement with a literature reported values. Decrease in mobility with the temperature was observed and its dependencies of T-13 and T-2.0 for moderately doped and low doped samples respectively were estimated. From deep level measurements by Minority Carrier Transient Spectroscopy, an influence of shallow boron related levels and D-center on dependence of on-state resistance was observed, being more pronounced in low doped samples. Similar tendency was observed in depth profiling of R-on. This suggests a major role of boron in a compensation mechanism thus resulting in high R-on.