Hot-carrier-induced dissociation of hydrogen-defect complexes in GaN and AlN 

Degradation of AlGaN-based ultraviolet light-emitting diodes (UV-LED) remains a challenge that limits their practical applications. Experiments indicate that the degradation is caused by point defects that may be activated by hydrogen dissociation, which enhances non-radiative recombination and trap-assisted tunneling. However, the microscopic mechanism of the hydrogen dissociation is unknown. Here we combine first-principles calculations with a Wannier-based tight-binding framework to analyze hot-carrier-stimulated hydrogen dissociation at hydrogen-defect complexes in GaN and AlN. We find that electron injection into antibonding orbitals (or hole injection into bonding orbitals) of the complex creates a strong repulsive interaction between the bonded atoms, leading to the femtosecond-scale bond dissociation. By treating the motion of hydrogen nuclei quantum-mechanically, we quantitatively describe the dissociation yield, enabling direct comparison with experiments. Given that hot carriers could be generated by Auger-Meitner recombination or excited by photons, our results suggest a dissociation pathway that could operate under device operation conditions.