Field enhanced diffusion of nitrogen and boron in 4H–silicon carbide

Abstract

A field enhanced diffusion (FED) model is proposed for the observed phenomenon of dopant migration within 4H silicon carbide (4H–SiC) during high temperature annealing. The proposed FED model is based on the combined effects of both dopant diffusion and the in-built p–n junction electric field gradients found within the doped substrate resulting from the presence of the substrate dopants. Measured as-implanted dopant concentration profile data prior to high temperature annealing are utilized as input data for the proposed FED model. The resultant FED profile predictions of the proposed model during annealing are shown to be in excellent agreement with experimental findings. Parameters are extracted using the FED model simulation for the high temperature ionic diffusivity and ionic field mobility for nitrogen dopant in boron co-doped 4H–SiC. The extracted values for the ionic diffusivity and the ionic mobility of the nitrogen donor in boron co-doped 4H–SiC found using the model are 7.2×10−15 cm2 s−1 and 1.6×10−13 cm2 V−1 s−1, respectively.