1. The problem statement, all variables and given/known data An abrupt Si p-n junction of cross sectional area 10-4cm-2 has the following properties: p side: number densities of acceptor impurity atoms: NA = 1017cm-3 minority carrier lifetime: τn = 0.1 us hole mobility: μp = 200cm2/Vs electron mobility: μn = 700cm2/Vs n side: number densities of donor impurity atoms: NA = 1015cm-3 minority carrier lifetime: τn = 10 us hole mobility: μp = 1300cm2/Vs electron mobility: μn = 450cm2/Vs (I've assumed that μp is hole mobility and μn is electron mobility although I'm not 100% on this) What is the reverse saturation current Is? 2. Relevant equations Reverse saturation current: Is = eA[(Dhpno / Lh) + (Denpo / Le)] Where, Dh = kTμh / e De = kTμe / e Lh = √(τhDh) Le = √(τeDh) pno = ni2 / NA npo = ni2 / ND 3. The attempt at a solution With these equations I should be able to find the reverse saturation current. However, I'm not entirely sure on which values of mobility μ I should be using. It seems like I can find the reverse saturation current in either the p side or the n side. I thought I'd work it out for both sides and hope that would be equal but I came a little unstuck when finding Lh and Le as it seems I need two values for τ on each side. In a PN junction, the reverse saturation current is due to the diffusive flow of minority electrons from the p-side to the n-side and the minority holes from the n-side to the p-side. I feel like I'm lacking some understanding, I was wondering if anyone could help clear this up for me?