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

Abstract

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 Sidoped GaN formed two dopant states, which were attributed to Si 3 N 4 and SiN x . From the Si K-edge XANES, the Si 3 N 4 state did not exhibit electronic states in the GaN bandgap, indicating inactive dopant sites in GaN, whereas the SiN x state exhibited bandgap states. Thus, the SiN x 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.

X-ray Absorption Fine Structural Study of Atomic Structures and Chemical States of Dopants in 4H-SiC(0001)

“…Figure shows the Si 1s core-level HAXPES spectrum for N-doped 4H-SiC(0001). The peak at 1840.4 eV is attributed to the Si–C species, while the peak at 1842.1 eV is due to the Si–N species. ,, …”

“…For the XANES simulations, we used FEFF9. ,− We employed full multiple scattering, self-consistent field, Hedin-Lundqvist (HL) exchange-correlation potential, and the final-state effect (Z+1 approximation). ,, …”

“…In the case of photon energy of 1486.6 eV, photoelectron kinetic energy is ∼1085 eV at the N 1s core level, while the kinetic energy is ∼120 eV in the case of photon energy of 520 eV. Because lower kinetic energy indicates more surface sensitivity, 17,34 the N−C species is predominantly formed near the surface. Note that the areal intensity ratio (I SiN /I SiC ) in the Si 2p spectrum (Figure S1) is 0.148, whereas the areal intensity ratio in the Si 1s spectrum (Figure 1) is 0.106.…”

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

“…In the case of X-ray diffraction, the atomic structures of dopants cannot be obtained due to the lack of periodicity with such dopants. Nevertheless, in the case of extended X-ray absorption fine structure and X-ray absorption near edge structure, they could provide information about the coordination number, the bond length between Mg and the surrounding atoms, and the unoccupied states of the Mg-dopant . However, the energy ranges of resonant absorption for the Mg K-edge and Ga L-edge overlap each other, showing little information on the Mg-dopant.…”

“…Nevertheless, in the case of extended X-ray absorption fine structure and X-ray absorption near edge structure, they could provide information about the coordination number, the bond length between Mg and the surrounding atoms, and the unoccupied states of the Mg-dopant. 27 However, the energy ranges of resonant absorption for the Mg K-edge and Ga L-edge overlap each other, showing little information on the Mg-dopant. Highresolution scanning transmission electron microscopy can clarify the atomic arrangement of the dopants in real space.…”