Q4 part d please Q4. a) With the aid of suitable labelled diagrams, describe the processes of carriergeneration and recombination in a semiconductor.b)Explain what is mean by the "mobility" of carriers in a conducting material,why electron mobilities are higher for electrons than holes, and why electronmobilities are higher in semiconductors like silicon than in a highlyconducing metal like copper.c) Explain how the electrical conductivity of a material depends on the freecarrier density and carrier mobility, and hence describe and explain thedifferences in the temperature dependences of the conductivity of anintrinsic semiconductor (e.g. pure silicon) compared with a good metal (e.g.copper).d) A silicon wafer has a p-type feature on its surface, with an acceptor densityof NA = 7.5 × 10²1 per m³, a length of 200μm and cross-sectional dimensionsof 15μm x 0.9μm. A voltage of 1.5V is applied across its length.(i)Calculate the conductivity of the p-type silicon, hence the drift currentdensity and the total drift current along the length of the doped feature.(ii) Calculate the sheet resistance of the p-type silicon and the resistanceof the doped feature.(iii) If the same p-type silicon is used in a pn diode with a built-in voltageof 0.70V, calculate the n-type doping density that is required.

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d) A silicon wafer has a p-type feature on its surface, with an acceptor density of NA = 7.5 × 1021 per m³, a length of 200μm and cross-sectional dimensions of 15μm x 0.9μm. A voltage of 1.5V is applied across its length. (i) Calculate the conductivity of the p-type silicon, hence the drift current density and the total drift current along the length of the doped feature. (ii) Calculate the sheet resistance of the p-type silicon and the resistance of the doped feature. (iii) If the same p-type silicon is used in a pn diode with a built-in voltage of 0.70V, calculate the n-type doping density that is required.