Part A seems fairly straight forward, It does not appear that 10^14 is <<10^16 s

Question

Part A seems fairly straight forward,

It does not appear that 10^14 is <<10^16 so we might have to consider high level. I am just unclear how to think about it. A concept is missing. Also, part B is not so clear for me. Thanks for any tips on how to approach this.

16 Assume a 1-dimensional silicon crystal, which has been doped with 10 cm3 arsenic atoms Using a light source, 1014 cm" additional electron-hole pairs are generated at x = 0 in steady state (dp/dt - dn/dt -0). (a) Can we consider low-level injection or do we have to assume high-level injection'? Justify your answer. (b) Calculate analytical expressions for the minority carrier distribution p.(x) in steady state for x > 0 for the following two cases (i) Infinitely long semiconductor with p,(x-o)- P.o (see sketch (i)) (ii) Semiconductor with length W and pn(x-W-Po (see sketch (11)) Hint: The electric field is zero INJECTING SURFACE INJECTING SURFACE ALL EXCESS CARRIERS EXTRACTED hv 0 0 P (x) P (o) p (o) no no 0 0

Explanation / Answer

we have injected carriers= 1014 cm-3.

These injected carriers are small as compared to the majority carrier density i.e.

ND= 1017 cm-3.

so the majority level carriers remains unchanged, while the minority carrier concentration strongly increases

So you can consider it as a LOW LEVEL INJECTION

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