The electrical conductivity is = e(n + n h ji h ) where e > and h are the

The electrical conductivity is

σ = e(n_εμ_ε + n_hji_h)

where μ_e > and μ_h are the electron and hole mobilities. For most semiconductors μ_e > μ_h.

(a) Find the net ionized impurity concentration ∆n = n_d⁺ – nd ^– for which the conductivity is a minimum. Give a mathematical expression for this minimum conductivity.

(b) By what factor is it lower than the conductivity of an intrinsic semiconductor?

(c) Give numerical values at 300 K for Si for which the mobilitics are μ_e 1350 and μ_h = 480cm² V^–3 s^–1, and for InSb, for which the mobilities are μ_e = 77000 and μ_h 750cm² V^–1 s^–1. Calculate missing data from Table 131,

Dielectric Density-of-states cffeative masses, in units of the free electron mass Energy Quantum concentrations of clectrons and holes constants, telative to gaps at 300 K at 300 K vacuunt eV em Cm Si Ge Gals InP InSb L.1 x 10 5.2 x 10 1.5 x 109 6.9 x 10 6.2 x 10" 1.14 0.67 1.43 135 0.18 2.7 x 10* 10 x 10" 46 x 10" 0.58 0.35 0.71 11.7 15.8 1.06 056 007 0073 0015 13.13 12.37 49 x 10" 0.42 46 x 10 17.58 0.39