A Theoretical Analysis of the Role of Ambipolar Diffusion in Charge-Carrier Transport in a Quasi-Neutral Region Under High Injection

A recent theoretical analysis considered charge collection from an ionization source in a p-n junction silicon diode under steady-state conditions, i.e., carrier liberation is at a quasi-constant rate, and concluded that the quasi-neutral region partitions into distinct sub-regions. A later empirical investigation (via TCAD simulations) found that this partitioning also applies under transient conditions, but a theoretical explanation was not given for the transient problem. The theoretical analysis given here provides that explanation, and also explains why a charge-collection model derived under steady-state conditions gives correct predictions for the transient problem.