3. The p-i-n diode shown schematically below is a three-region device with a middle region that is intrinsic (actually lightly doped) and relatively narrow. Assuming the p- and n-regions to be uniformly doped and ND - NA = 0 in the i-region: (a) Roughly sketch the expected charge density, electric field, and the electrostatic potential inside the device. Also draw the energy band diagram for the device under equilibrium conditions. (b) What is the built-in voltage drop between the p- and n- regions? Justify your answer. (c) Establish quantitative relationships for the charge density, electric field, electrostatic potential, and the p- and n-region depletion widths. P - 지 2 2 N

Fig: 1