Silicon (Si) is to be doped with Boron (B) such that the extrinsic semiconductor has a...

Transcribed Image Text:

Silicon (Si) is to be doped with Boron (B) such that the extrinsic semiconductor has a room temperature electrical conductivity of 0.08 (2m)-1. To achieve this, B atoms are diffused into a pure crystalline Si wafer using a heat treatment conducted at 900C for 286.5 hours. The surface concentration of B is to be maintained at a constant level of 3.0x1024 atoms/m. The values of activation energy and pre-exponential are 3.87eV/atom and 2.4x10-3 m/s, respectively. Si has a density of 2.33g/cm, an intrinsic conductivity of 4x10-4 (2m)-1, with e = 0.19 m/Vs. B has a density of 2.34 g/cm. Assume that B atoms substitute for Si atoms and saturation is reached. (i.) (ii.) (iii.) Find the concentration of B in Si at a depth of 1.0m from the surface. Assuming the value from (i) to be the equilibrium concentration of B in Si, find: a. The atomic % of B in the Si sample. ( ) b. The charge carrier mobility of this sample. (Hint: what is the dominant charge carrier in this extrinsic semiconductor?) ( ) The electrical conductivity of this sample if it was further doped with an additional 5x1018 atoms/m B. Silicon (Si) is to be doped with Boron (B) such that the extrinsic semiconductor has a room temperature electrical conductivity of 0.08 (2m)-1. To achieve this, B atoms are diffused into a pure crystalline Si wafer using a heat treatment conducted at 900C for 286.5 hours. The surface concentration of B is to be maintained at a constant level of 3.0x1024 atoms/m. The values of activation energy and pre-exponential are 3.87eV/atom and 2.4x10-3 m/s, respectively. Si has a density of 2.33g/cm, an intrinsic conductivity of 4x10-4 (2m)-1, with e = 0.19 m/Vs. B has a density of 2.34 g/cm. Assume that B atoms substitute for Si atoms and saturation is reached. (i.) (ii.) (iii.) Find the concentration of B in Si at a depth of 1.0m from the surface. Assuming the value from (i) to be the equilibrium concentration of B in Si, find: a. The atomic % of B in the Si sample. ( ) b. The charge carrier mobility of this sample. (Hint: what is the dominant charge carrier in this extrinsic semiconductor?) ( ) The electrical conductivity of this sample if it was further doped with an additional 5x1018 atoms/m B.