1. The problem statement, all variables and given/known data The drift current in a p-n junction is 20μA . Estimate the number of electrons crossing a cross section per second in the depletion region. 2. Relevant equations Drift current is the current that occurs due to formation of holes and electrons in the depleted region from where the electrons and the holes are sucked away to the respective sides . This creates a current from n to p . Called the drift current The drift current is a result of flow of both holes and electrons. 3. The attempt at a solution So the electrons and the holes both equally contribute to the drift current . So the current due to the electrons would be 10μA . So that means 10 * 10^(-6) C flowing per second charge on one electron = 1.6 * 10^-19 C so we can write n * 1.6 * 10^-19 C =10 * 10^(-6) n = 6.25 * 10^13 electrons . But the answer given is 3.125 * 10 ^ 13 , half of what I calculated . Where am I wrong ?