Electron and hole concentrations increase with temperature. For pure silicon, suitable expressions are h =

Electron and hole concentrations increase with temperature. For pure silicon, suitable expressions are ρ_h = −ρ_e = 6200T^1.5e⁻⁷⁰⁰⁰/T C/m³. The functional dependence of the mobilities on temperature is given by μh = 2.3 × 10⁵T^−2.7 m²/V · s and μ_e = 2.1 × 10⁵T^−2.5 m²/V · s, where the temperature, T, is in degrees Kelvin. Find σ at:

(a) 0◦C;

(b) 40◦C;

(c) 80◦C.