Question

Find the electron diffusion and drift currents at x, in ap*-n junction D q-V kT for V? kT e P L2 v.b x)I q-V D. ид. "а. .V.b-(0"x) I = I L Assuming space charge neutrality, the excess hole distribution is equal to the excess electron distribution on(x) = op(x) q-V dбр IXiqAD dx kT Pm e diff q-V I (x I (x)-(x) A D. D kT 1 e e diff drift T T L'p n or

i don't get it why the whole current is like that
can u explain in detail?

Answer 1

Its because ,

At any point in the quasi neutral region, the total current is given by

I_total= I_n +I_p

where I_n is current due to elecron and I_p is due to holes.

Now each current component corresponding to holes or electrons is made up of drift and diffusion currents.

And since it is p+ n diode , the n type will be minority carrier in the p region where x_n=0 , so they are approximating total current at the edge to be that of only holes and current due to electrons is assumed to be zero.

Hence you are seeing that,.