Direct Observation of Atomic Structures and Chemical States of Active and Inactive Dopant Sites in Mg-Doped GaN

We employed photoelectron spectroscopy (PES) and photoelectron holography (PEH) to clarify the atomic structures and chemical states in the active and inactive dopant states of Mg-doped GaN. Due to the lack of available direct evidence, this has been a controversial issue. From PES, we found that two chemical states existed in the Mg-doped GaN: One is an active dopant state, and the other is an inactive state. We employed PEH to investigate the two observed chemical states, indicating that the active state could be attributed to a Mg atom substituting a Ga atom in the Mg-doped GaN structure (Mg-Ga). The inactive state, on the other hand, was considered to be a disordered structure, an amorphous structure, defects, and/or MgGa bonding with a H atom in that structure.