3. Assume that the donor concentration in an n-type semiconductor at T = 300 K is given by Na(x) = 106-1015x (cm-3) where x is in cm and 0 x 0.01 cm. The electron mobility is, n = 960 cm V.S (i) Calculate: (a) the electronic diffusivity D and (b) the electron diffusion current. (ii) (a) Find an expression for the induced electric field E(x), which brings the semiconductor slab back into equilibrium and (b) calculate its value at x = 0.