Characteristics of Irregular Forward Current Conduction in 4H-SiC pn Junction Diodes

Abstract

SiC diodes show an irregular forward current conduction deviating from the standard diode theory, JF∝exp (VF), where JF is the forward current conduction density and VF is the forward voltage. However, it is not known whether this irregular conduction is due to defects formed by ion implantation or to native defects in the epitaxial layer. This paper reports how we analyzed an irregular forward current conduction in 4H-SiC pn junction diodes by a combination of gate-controlled diodes and X-ray topography. We found that one of the two irregular forward current conductions is due to defects formed by ion implantation, and the other conduction was due to the defects penetrating the pn junction. An x-ray topography image showed that the quantity of isolated native defects in the epitaxial layer does not affect the forward current conduction and that “linear defect” could be observed when the forward current conduction is particularly irregular.