Drift-diffusion solution wihtout using Plasma module

I want to use comsol to solve drift-diffusion and Poisson equation in a coupled manner for a wire that has variable resistance (or charge density) across it. Charge density at each location depends on the potential that is present at that point. I need the solution in a 2D-axisymetric geometry. Currently, I can do the Poisson part easily using the comsol 4.3a that we have in our lab. However, our version does not have the Plasma module that I need for solving Drift-Diffusion.

In such case, please suggest me alternate ways of solving drift-diffusion without using the plasma module.