High-level injection in quasi-neutral region of n/p junction devices: Numerical results and empirical model

The ambipolar transport equation is solved numerically to provide the physical insight of high-level free-carrier injection in the quasi-neutral region of n/p junction devices. It is shown that the diffusion current-only approximation used conventionally to model the minority current fails when high-level injection prevails. Our results further suggest that in high-level injection, the drift current is comparable to the diffusion current and that the minority current in the quasi-neutral region is position dependent even if the region is thin. Based on the numerical results, an empirical model is also developed which, while retaining the form of the conventional diffusion current-only model, can accurately describe the current transport in an n/p junction including the effect of high injection.