The ambipolar transport equation for p-type semiconductor is
\(\rm {{\text{D}}_{\text{n}}}\frac{{{\partial ^2}\left( \delta{{\text{n}}} \right)}}{{\partial {{\text{x}}^2}}} + {{\text{}}\mu_{\text{n}}}{\text{E}}\frac{{\partial \left(\delta {{\text{n}}} \right)}}{{\partial {\text{x}}}} + {\text{g'}} - \frac{{{\delta\text{n}}}}{{{{\text{ }}\tau_{{\text{no}}}}}} = \frac{{\partial \left( \delta{{\text{n}}} \right)}}{{\partial {\text{t}}}}\), where all notations have standard meaning. Which term is set to zero when no excess carrier recombination is assumed?
1
\(\rm \frac{{{\partial ^2}\left( {{\rm{\delta n}}} \right)}}{{\partial {{\rm{x}}^2}}} = 0\)
2
\(\rm \frac{{\partial \left( {{\rm{\delta n}}} \right)}}{{\partial {\rm{x}}}} = 0\)
3
\(\rm \frac{{{\rm{\delta n}}}}{{{{\rm{\tau }}_{{\rm{no}}}}}} = 0\)
4
\(\rm \frac{{\partial \left( {{\rm{\delta n}}} \right)}}{{\partial {\rm{t}}}} = 0\)