Reference no: EM132522057

Question 1) The electrical resistivity of pure silicon is 3 x 103 ohm·m at room temperature (300 K). Determine the conductivity at 250°C. (band gap of Si=1.1 eV)

Question 2) For Germanium at 25 ?, estimate  

1. The number of charge carriers, 
2. The fraction of the total electrons in the valence band that are excited into the conduction band 
3. The constant σ0. (hint: the constant that appears in temperature dependence of intrinsic semiconductors) 

Given: ρ (Ge, 25 ?) = 43 Ω.cm, Eg=0.67 eV, µe=3900cm2/V.s, µh=1900cm2/V.s, lattice parameter of Ge is 5.6575 Å, in cubic ZnS type structure there are 8 atoms/cell 

Question 3) Estimate the probability of thermally exciting an electron to the conduction band in diamond (Eg = 5.6 eV) at 25?? Hint: Use the Fermi distribution function introduced in the last slides of Electrical Properties part I and for semiconductors/insulators, the Fermi energy of the material is located in the middle of the band gap. 

Question 4) A liquid nitrogen dewar is made up of steel with a yield strength of 350 MPa. The steel is constrained from contracting and sustains a temperature difference of 150? when filled with liquid nitrogen. If the coefficient of thermal expansion is of this steel is 9x10-6, what thermal stress is produced? Use elastic modulus of this steel as 193 GPa.