We present results from ab-initio local-orbital calculations performed to study the impact of ammonia on GaN. We focus on chemical reactions on the non-polar (101̄0) and (112̄0) surfaces as well as the dissociative adsorption of NH3 on GaN(0001̄), for which an energy barrier is obtained by computing the potential energy surface. For the adsorption of NH3 on GaN(0001̄), finite-temperature molecular-dynamics simulations show that the molecule splits into NH2 and H. The NH2 group binds to two of the three second-layer Ga atoms neighboring the vacancy, while the dissociating H binds to a first-layer nitrogen atom. This reaction lowers the total energy of the system by 2.05 eV. The energy barrier estimated for dissociative adsorption of NH2 and H on the vacancy p(2×2) reconstruction of the GaN(0001̄) surface is 0.5 eV.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Condensed Matter Physics
- Surfaces and Interfaces