Atomic Structures and Chemical States of Active and Inactive Dopant Sites in Si-Doped GaN

The atomic structures and the electronic states of active and inactive dopant sites in semiconductor are elucidated successfully by using X-ray absorption near-edge structure (XANES), Auger electron spectroscopy (AES), and photoelectron spectroscopy (PES). To demonstrate the versatility of this method, we investigated Si-doped GaN as a prototype and clarified the atomic structures and chemical states at the active and inactive dopant sites in GaN. From AES and PES, it was found that Si-doped GaN formed two dopant states, which were attributed to Si3N4 and SiNx. From the Si K-edge XANES, the Si3N4 state did not exhibit electronic states in the GaN bandgap, indicating inactive dopant sites in GaN, whereas the SiNx state exhibited bandgap states. Thus, the SiNx state should act as an active dopant site in Si-doped GaN. The simulated XANES spectra well reproduced the electronic state in the GaN bandgap when the Ga atom is replaced by the Si atom, suggesting that the active dopant site may be the Si-substituted Ga sites.