Maybe you can solve it-------How to edit/ add a semiconductor doping model in a p-n junction?

Hi there,

I am learner of Comsol. I have simulated a p-n junction according to help documents step by step, and it worked. But now I want to change the doping profile in the n domain. How should I do ? I used the semiconductor doping model that in Comsol but its equation seems to fixed, which I can not make any changes of it. Is there anyway I can edit it or maybe adding a new doping profile model which I could edit ? Basically I aimed to add an interval of charge distribution in the n domain. I am very appreciated if you can give me some suggestions .

Thank you very much!