3.11 Holes are being steadily injected into a region of n-type silicon (connected to other devices, the details of which are not important for this question). In the steady state, the excess-hole concentration profile shown in Fig. P3.11 is established in the n-type silicon region at room temperature. Here “excess” means over and above the thermal-equilibrium concentration (in the absence of hole injection), denoted pn0. If ND = 1016/cm3, ni = 1.5 × 1010/cm3, Dp = 12 cm2/s, and W = 50 nm, find the density of the current that will flow in the x direction.