Question

The electron concentration gradient of some material is dn/dx=10¹⁷cm^-4, and the

Constant Table:

e₀ =8.85´10^-12C²×N^--1×m^-2 ; R=8.315J-mol^-1×K^-1; m₀= 4π´10^-7N×A^-2; h = 6.63´10^-34J×s;

e = 1.602´10^-19C; G=6.67´10^-11N×m²-kg^-2; m_e=9.11´10^-31kg; g=9.8 m/s²;

mobility of the electron is 1350 cm²/V.s，calculate:

(a) the diffusion coefficient of the electron, assuming kT=0.0259ev at T = 300 K.

(b) the diffusion current density of electrons.

Answer 1

a)

By using the Einstein relation between diffusion coefficient and mobility,

where Dn= diffusion coefficient of electrons

So,

Given, mobility = 1350 cm^2/V-s

And kT/q = 0.0259 eV

So

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B)

Diffusion current density of electrons = Jn

Given, dn/dx=10¹⁷cm^-4

q = 1.602´10^-19C

So

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