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Consider a long rectangular bar of direct bandgap p-type semiconductor. The equilibrium hole density is 1017 cm−3 and the intrinsic carrier concentration is 1010 cm−3. Electron and hole diffusion lengths are 2 μm and 1 μm, respectively.
The left side of the bar (x = 0) is uniformly illuminated with a laser having photon energy greater than the bandgap of the semiconductor. Excess electron-hole pairs are generated ONLY at x = 0 because of the laser. The steady state electron density at x = 0 is 1014 cm−3 due to laser illumination. Under these conditions and ignoring electric field, the closest approximation (among the given options) of the steady state electron density at x = 2 μm, is _______
A
0.37 × 1014 cm−3
B
0.63 × 1013 cm−3
C
3.7 × 1014 cm−3
D
103 cm−3

Correct : a

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