Phys Chem Chem Phys. 2025 Oct 29. doi: 10.1039/d5cp02522b. Online ahead of print.
ABSTRACT
It has been demonstrated that quantum effects play an important role in nitrogen adatom diffusion over partially Ga-covered GaN(0001) surfaces. This is partially related to the bonding in both the initial and activated complex states. It is shown that wurtzite gallium nitride is bonded differently from standard semiconductors having two separate valence subbands: upper by gallium 4sp3 hybridized orbitals and nitrogen resonant 2p states, and lower by gallium 3d and nitrogen 2s orbitals. Second, the diffusion energy barrier may be changed owing to the quantum statistics of electrons governed by the Fermi energy, as shown in the case of nitrogen diffusion over a clean and gallium-covered Ga-terminated GaN(0001) surface. Under fractional Ga coverage of the GaN(0001) surface, the nitrogen diffusion energy barrier is at the saddle point. The barrier affects the electron redistribution between the surface quantum states at both the initial and saddle points. In the case of full GaN coverage, the diffusion path is from the top N adatom configuration to the H3 site, which corresponds to the maximal energy. Therefore the diffusion barrier is ΔEbar = 1.18 eV for clean and ΔEbar = 0.92 eV for (1/6) ML to finally ΔEbar = 1.23 eV for full Ga coverage. Thus, the overall barrier was ΔEbar = 0.92 eV. The identified stable N-on-top configuration for Ga coverage is essential for the GaN growth mechanism.
PMID:41159340 | DOI:10.1039/d5cp02522b
