Consider two cases: (a) a n-type substrate, doped ND=10 cm", with a p* step junction, doped NA=10 7cm, bonded directly to it; vs. (b) a diffused player on the same substrate at "1" but linearly dropping from NA=10 7cm at the substrate surface to NA=10 4cm at 3 um depth. Calculate what the grading parameter is in case "b". Calculate the values of the space-charge region widths, -xp and +xn for both cases "a" and "b"