Electronic structure and chemical bonding anisotropy investigation of wurtzite AlN

Abstract

The electronic structure and the anisotropy of the AlN and chemical bonding of wurtzite AlN has been investigated by bulk-sensitive total fluorescence yield absorption and soft x-ray emission spectroscopies. The measured N K, Al L 1 , and Al L 2,3 x-ray emission and N 1s x-ray absorption spectra are compared with calculated spectra using first-principles density-functional theory including dipole transition matrix elements. The main N 2p-Al 3p-Al 3d and N 2p-Al 3s hyridization regions are identified at −1.0 to −1.8 eV and −5.0 to −5.5 eV below the top of the valence band, respectively. In addition, N 2s-Al 3p and N 2s-Al 3s hybridization regions are found at the bottom of the valence band around −13.5 and −15 eV, respectively. A strongly modified spectral shape of Al 3s states in the Al L 2,3 emission from AlN in comparison to Al metal is found, which is also reflected in the N 2p-Al 3p hybridization observed in the Al L 1 emission. The differences between the electronic structure and chemical bonding of AlN and Al metal are discussed in relation to the position of the hybridization regions and the valence-band edge influencing the magnitude of the large band gap.

Electronic structure of GaN and Ga investigated by soft x-ray spectroscopy and first-principles methods

“…Electronic dipole transitions over the band gap thus essentially involve the N 2p states of the valence band and the unoccupied Ga 4s states of the conduction band. In comparison to AlN, 10 the Ga 3d semicore level generally stabilizes the crystal structure of w-GaN as no 3d states are located at the very top of the valence-band edge in GaN. Furthermore, by looking at Fig.…”

“…SXE of GaN has been utilized at the Ga L 3 edge, but the position and shape of the weak Ga 4s valence states could not be resolved or identified. 9 Contrary to the case of the wide band-gap nitride AlN, 10 where the populated A 3d states ͑here A denotes the IIIB element Al͒ are located at the very top of the valence band, the Ga 3d states in GaN are located at the bottom of the valence band and therefore the N 2p-A 3d interaction plays a different role than in AlN. In N K emission of GaN, a small peak structure has been observed at the bottom of the valence band around −17 to −19 eV ͑Refs.…”

Electronic properties and bonding characteristics of AlN:Ag thin film nanocomposites

“…Region (i) is mainly due to N 2s-Al 3s and N 2s -Al 3p hybrid states around À21.5 and -20 eV, respectively, in agreement with other electronic structure calculations. 1 Interestingly, although less pronounced, the occupation of Al 3d states is found around À20 eV which is mainly characterized by Al 3p-N 2s hybridization, whereas in this region Ag contributions are absent. The lower part of Region (ii) is mainly due to N 2p-Al 3s-3p hybridizations, while the N 2p -Al 3p-3d electrons participate in the upper part.…”

“…Moreover, AlN is included within the direct wideband-gap (6.2 eV) materials (AlN, GaN and SiC) that are considered to be the third generation of semiconducting materials in the microelectronic industry. [1][2][3][4][5][6] In addition, AlN thin films when doped with rare earth impurities (Er 3þ , Tb 3þ ) exhibit photo-emission lines corresponding to intra-4f| n -shell transitions in the ultraviolet and visible spectra region, making these films potential candidates for optical communication systems based on silica fibers that could constitute the backbone of long distance telecommunications and high speed data transfer networks. [7][8][9] Furthermore, crystalline ternary early transition-metal nitrides (Ti 2 AlN and Sc 3 AlN) exhibit a technologically important combination of metallic and ceramic properties.…”

Chemical structure of vanadium-based contact formation on n-AlN

“…These 2 techniques have previously been used successfully to shed first light on the V-based contact formation on n-GaN [8]. XES has also been widely used to investigate the electronic structure of GaN, AlN, and their alloys [9,10,11]. Here, XES was used to investigate the local atomic environment of nitrogen and vanadium of Au/V/Al/V/n-AlN structures before and after RTA treatment.…”