Carrier Generation and Recombination

Carrier generation refers to the creation of electron-hole pairs.

Band-to-band generation occurs in direct band gap semiconductors via thermal excitation or photon absorption. In such semiconductors, the valence band maximum and conduction band minimum have the same momentum.

Indirect generation of carriers occurs by absorbing lattice energy from phonons and is dominant in indirect-bandgap semiconductors, which have their valence band maximum and conduction band minimum at different momenta.

In Auger generation, carriers are generated by consuming the energy of a highly energetic particle. These same high energy particles can generate multiple electron-hole pairs using the available high electric field during impact ionization.

In contrast, Recombination is the process of the annihilation of electrons and holes.

In Band-to-band recombination, the electron transitions from the conduction to the valence band, releasing a photon.

During indirect recombination, localized energy states called traps are utilized for transitions between the conduction and valence bands, releasing energy as heat.

Auger recombination involves the recombination of an electron and a hole, transferring the resulting energy to another carrier.