It has been discovered that holeelectron pair recombination in ntype nitrogendoped gallium phosphide GaP is predominantly radiative emitting green light A certain device designer wants to make green GaP lightemitting diodes and has the following materials available to use in his design ntype N2doped ND 1018 cm3 ntype N2doped Np 5 1016 cm3 ptype Zndoped NA 1018 cm3 ptype Zndoped NA 5 1016 cm3 In each instance De 25 cm2s D1 5 cm2s and 106 s a Which is the best combination of materials to use to make an efficient green lightemitting pn junction diode Explain your answer b In a GaP green LED we want the holes injected into the nside to recombine in the semiconductor and not at the ohmic contact Thus the nside should be much wider than a minority carrier diffusion length How wide wn should the n JUNCTION DIODES 183 side be to ensure that less than 10 percent of the injected carriers recombine at the contact GaP is costly so find a lower limit for the width w Use reasonable c When designing this device is it better to select the width of the pside so that approximations it operates in the longbase limit or shortbase limit or does it matter Explain your answer d Consider for the sake of argument a GaP LED that is sufficiently thick that it operates in the longbase limit on both sides of the junction that is wp Le Wn Lh Assume also that the device is doped as you said it would be in part a above When the diode is forwardbiased what fraction of the total current is carried by electrons at the following positions in the device and why i In the depletion region at the junction ii Inside the semiconductor close to the ohmic contact on the pside iii Inside the semiconductor close to the ohmic contact on the nside