1. The problem statement, all variables and given/known data An extrinsic semiconductor sample of cross section A and length L is doped in such a way that the doping concentration varies as Nd=N0 Exp(-x/L) Assume that mobility μ of the majority carriers remain constant.What is the resistance of the sample? 2. Relevant equations σ=neμ ρ=1/σ R=Lρ/A=L/(Aμen) 3. The attempt at a solution In the eqn n is the free electron concentration. I thought this will be eqal to doping concentration. then,R = L/(AμeNoExp(-x/L)) But this is not the right answer. Can this resistance be varrying with x since doping concentration depend on x? Thanks.