Upon some calculation I arrive to the expression:
d2DPn(x)/dx2 = DPn(x)/Lh2
Where:
DPn(x) = Pn(x) + Pno - excess minority carriers (holes) concentration in the n-type part of the pn junction.
Now the roots to the characteristic equation are +/- 1/Lh where Lh is the length of the...