Q4. (a) In the absence of an electric field E and generation G, the continuity -=D, 0 SP- a8p Sp Solve Tp equation for holes can be expressed as asp at the equation to show that the steady-state excess carrier concentration for holes can be expressed as Sp(x)= Ape" and draw a characteristic diagram showing the variation of & as a function of x. The symbols carry their standard notations. (b) A Si p-n junction with a cross-sectional area 0.001 cm has N, = 5x1015 /cm, and N =1x107 /cm. Assuming =1350 cm/V-s, H, =480 cm/V-s, and r, = r, =2.5 ms, i. Calculate the current with a forward bias of 0.7V. ii. Which type of carrier contributes to most of the current? iii. If you wanted to double the electron current, what should you do?