Nonradiative electron-hole recombination by a low-barrier pathway in hydrogenated silicon semiconductors

A microscopic pathway for nonradiative electron-hole recombination by large structural reconfiguration in hydrogenated Si is found with first-principles calculations. Trapped-biexciton formation leads to a low-barrier reconfiguration of the H atom, accompanied by crossing of doubly occupied electron and hole levels in the band gap. This crossing represents the nonradiative recombination of the carriers, without multiphonon emission. The proposal provides a mechanism for carrier-induced H emission during metastable degradation of hydrogenated amorphous silicon.