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Q4 Consider a pn junction diode at 300 K in which the p doping density is 10²4 m²³ while the n doping density is 1022 m³. The thickness of the p-doped region is 10 um while the thickness of the n-doped region is 20 µm and the cross-sectional area of the diode is 2 μm². Take kT=0.025 V, kT/q-0.025 eV, the intrinsic carrier concentration n; to be 1.5x10¹6 m³ at 300K, the diffusion constant for the electrons De to be 0.0038 m²/s and the diffusion constant for the holes Dh to be 0.0012 m²/s. a) Describe in words the two approaches used to calculate the contact potential at equilibrium. (4 marks) b) i) Calculate contact potential at equilibrium and the total depletion layer thickness. (2 marks) ii) Calculate the maximum electric field strength and say where it is located. (2 marks)