I assume you are using the short base mode, so lifetime due to SRH is not a major concern---your current is drift current. With this assumption in mind,two diodes with n=1 and n=2 makes big sense in physics. So you can use silvaco to get ib semilog plot and use n=1 and n=2 two diodes mode to fit get j01 and j02. They are your indicators of epi quality and junction quality. Well under low injection level.