Concerted diffusion, clustering, and magnetic properties of Mn dopants on a 2 x 2-T4 GaN(0001) substrate

Based on first-principles calculations within density functional theory, we propose a kinetic pathway for Mn incorporation on reconstructed 2 x 2-T4 GaN(0001), characterized by concerted substitution of a Ga atom by a Mn adatom via a precursor surface site T4. The Mn dopants at low densities are randomly distributed, resulting in intrinsic diluted magnetic semiconductors (DMS). At high Mn densities, planar ferromagnetic clusters oriented in the (0001) plane can be readily formed at relatively low growth temperatures, but ferrimagnetic zigzag columns along the growth orientation will be formed at high temperatures. Furthermore, intrinsic DMS are more likely to be formed via codeposition of Mn+Ga+N at high growth rates. These findings help to explain the observed variations in both the magnetic ordering temperature TC and the magnetic nature of Ga1-xMnxN.