2.6 Trapping and Recombination

By their very nature, traps capture charge carriers. It is critical to understand their effects on a device in order to judge their relevance. Trapped charge carriers contribute to the space charge (see Eq. ??), without contributing to charge transport. Additionally, trap levels introduce another recombination pathway. Both effects are typically bad for device performance.

In transient simulations, things get a little bit more complicated as the trapping and/or detrapping can take rather long and, therefore, it might take a long time (as compared to the simulated time) before equilibrium is reached. This is especially relevant to cases where there is a distribution of traps, giving rise to multiple trapping/detrapping times.

In sum, traps can have a large impact on the simulations, depending on what is simulated and in what regime.

The non-geminate recombination of electrons and holes can proceed via different mechanisms: direct or band-to-band recombination; trap-assisted or Shockley-Read-Hall (SRH) recombination; and surface recombination. ¹ Surface recombination is described in section 2.2.