a) Draw the band edge diagram of a pn-junction at equilibrium [5pt]. Label regions where you would expect diffusion and/or drift currents. b) Draw the current versus voltage behavior you would expect if you hooked up a voltage power supply to the junction. Clearly label which electrode goes to which end of the pn-junction so I can see if you understand how the diode works [3pt]. c) What happens under forward bias? Where do the electrons and holes go? Draw a picture to make things clear [3pt]. d) What happens under large reverse bias? Do you get any current? If so how? Draw a picture to make things clear [3pt]. e) What would you add/change in this structure to make a good LED? Draw a picture to make things clear [3pt]. f) What would you do to the LED you made in part (e) to make it into a laser? Draw a picture to make things clear [3pt].