Analytical Model and Optimization for SiC Floating Island Structure

Conventional power semiconductor devices suffer from a well-known performance limit. Floating Island (FI) structure can break the limit by inserting multiple oppositely doped islands into the drift layer and is suitable for silicon carbide (SiC) devices. In this article, the FI devices are classified into two distinct types according to the doping level of the islands, which are referred to as field-stop FI (FSFI) with highly doped island and fully depleted FI (FDFI) with medium-doped island. The theoretical limits for both types are revealed through 1-D modeling. The FDFI is found to be endowed with 12% lower specific ON-resistance than FSFI. To facilitate the comprehensive design of FDFI devices, 2-D analytical models for both conducting state and blocking state are established and verified by numeric simulation. By virtue of the 2-D models, charge balance effect of FDFI is illuminated, and parametric optimization for 2-, 4-, and 6-kV rated devices is performed. The optimal designs are presented and also simulated numerically. The results from models and numeric simulations show good agreement. The analytical models in this article are proved to be rather effective and can be helpful in revealing the mechanism of FI devices as well as in optimizing FI devices.