Chapter 1, Problem 1.4TYU

The electron and hole diffusion coefficients in silicon are $D_n=35{\text{cm}}^{\text{2}}\text{/s}$ and $D_p=12.5{\text{cm}}^{\text{2}}\text{/s}$ , respectively. Calculate the electron and hole diffusion current densities (a) if an electron concentration varies linearly from $n={10}^{15}{\text{cm}}^{-3}$ to $n={10}^{16}{\text{cm}}^{-3}$ over the distance from $x=0$ to $x=2.5\mu \text{m}$ and (b) if a hole concentration varies linearly from $p={10}^{14}{\text{cm}}^{-3}$ to $p=5\times {10}^{15}{\text{cm}}^{-3}$ over the distance from $x=0$ to $x=4.0\mu \text{m}$ . (Ans. (a) $J_n=202{\text{A/cm}}^{\text{2}}$ , (b) $J_p=-24.5{\text{A/cm}}^{\text{2}}$ )