Investigation of electrical contacts to p-Grid in SiC power devices based on charge storage effect and dynamic degradation

Abstract

P‐grid is a typical feature in power devices to block high off‐state voltage. In power devices, the p‐grid is routinely coupled to an external electrode with an Ohmic contact, but Schottky contact to the p‐grid is also proposed/adopted for certain purposes. This work investigates the role of contact to p‐grid in power devices based on the commonly adopted technology computer‐aided design (TCAD) device simulations, with the silicon carbide (SiC) junction barrier Schottky (JBS) diode as a case study. The static characteristics of the JBS diode is independent of the nature of the contact to p‐grid, including the forward voltage drop (VF) and the breakdown voltage (BV). However, during the switching process, a Schottky contact would cause storage of negative charges in the p‐grid, which leads to an increased VF during switching operation. On the contrary, an Ohmic contact provides an effective discharging path for the stored negative charges in the p‐grid, which eliminates the dynamic degradation issues. Therefore, the necessity of an Ohmic contact to p‐grid in power devices is clarified.