I'm wondering how this actually can be solved since i think there is one piece missing. 1. The problem statement, all variables and given/known data Determin the diffusion length L on a P+N diode with Nd = 10^16 cm^-3 in the N region. 2. Relevant equations Known is that Diffusion length can be found from L=sqrt(Dt) 3. The attempt at a solution As D = kT/q*u where u can be determined using a electron and hole mobility graph. But now how can i find t? It is not staded what t is.