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This is for solid state electronics: Problem 4: Excess electrons and holes are generated at the...

This is for solid state electronics:

Problem 4:
Excess electrons and holes are generated at the end of a Si bar (at x=0).
The Si is homogeneously doped with P atoms to a concentration of 1017 cm-3.
The minority carrier lifetime = 1 μs.
The electron diffusion coefficient = 25 cm2/s
The hole diffusion coefficient = 10 cm2/s
The excess electron and hole concentrations at x=0 are equal to each other and are 1015 cm-3.
(a) Write the formula (with all known numerical values substituted) for the Steady‐state nonequilibrium
minority carrier concentrations in the Si for x>0.
(b) Calculate the steady‐state non‐equilibrium minority carrier concentrations for x=31.6 μm.
(c) Calculate the steady‐state non‐equilibrium minority carrier concentrations for x=1000 μm.
(d) Repeat (b) and (c) to calculate the total steady‐state minority carrier concentrations.


Answers: (b) 3.68x1014 cm‐3s‐1, (c) ≈ 0 cm‐3s‐1, (d) Hint: Determine n0, p0, and remember that n(x)=n0+δn(x) or p(x)=p0+δp(x) .

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