SiドープGaN(0001)におけるドーパントの活性サイト・不活性サイトの化学状態解明

抄録

We have investigated the electronic states of active and inactive dopant sites in Si-doped GaN using the X-ray absorption near-edge structure (XANES), Auger electron spectroscopy (AES), and photoelectron spectroscopy (PES). From AES and PES, it was found that Si-doped GaN contains Si₃N₄ and SiN_x dopant states. According to Si K-edge XANES, the Si₃N₄ state does not exhibit electronic states in the GaN bandgap, indicating that these dopant sites in Si-doped GaN are inactive, whereas SiN_x exhibited bandgap states. Thus, the SiN_x state should act as an active dopant site in Si-doped GaN. The simulated XANES spectra accurately reproduce the electronic state in the GaN-bandgap where a Ga atom is replaced by a Si atom, suggesting that these are the active dopant sites. Inactive dopant sites (Si₃N₄) in Si-doped GaN are formed predominantly close to the surface. Since Ga vacancies are formed largely at sites close to the surface, it is apparent that the quantity of Ga atoms or its vapor should be optimized to prevent formation of Ga vacancies thus avoiding population of the inactive sites.