Modification of the N bonding environment in GaN after high-dose Si implantation: An x-ray absorption study

Abstract

The microstructure and electronic structure of epitaxially grown GaN, that has been subjected to high-dose Si implantation, is studied using x-ray absorption fine structure (XAFS) spectroscopy. More specifically, XAFS is used to probe the formation of N–Si bonds and to study the implantation induced distortions in the lattice. The analysis of the extended XAFS spectra reveals that implantation with 100keV Si ions with a fluence equal to 1×1018cm−2 renders the material amorphous and promotes the formation of Si–N bonds with a bond length equal to that corresponding in Si3N4. In addition to that, the N–Ga distances increase by ∼5% due to the lattice expansion caused by the incorporation of the Si ions and the formation of point and extended defects. The absence of long or midrange order is also verified by the near edge XAFS (NEXAFS) spectra where the characteristic peaks are smeared out. However, a characteristic sharp resonance line, that appears about 1eV above the absorption edge, indicates the existence of defect states which are strongly localized on the N atoms, most probably defect complexes involving N dangling bonds. In order to provide additional evidence on the nature of the implantation induced changes we resorted to simulations of the NEXAFS spectra using the FEFF8 code by applying chemical and lattice deformations in the immediate environment of the absorbing atom as well as to larger clusters.

X-ray absorption study of defects in reactively sputtered GaN films displaying large variation of conductivity

“…The present work attempts to investigate the nature of defects in unintentionally doped GaN by x-ray absorption spectroscopy (XAS), exploiting the control over nitrogen incorporation and the consequently large variation of conductivity of these films, which are facilitated by reactive sputtering. Both extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) techniques, which are widely used to investigate local structure have also been applied to GaN films [45][46][47][48][49][50][51][52][53][54], although mostly for the fingerprinting of cubic and hexagonal symmetries and for exploring the coexistence of polytypes in mixed phase GaN [45,46]. There are also some reports on the investigation of the nature of point defects arising from Ar + bombardment and low energy ion implantation of MBE and MOCVD grown GaN films [47][48][49][50].…”

“…Both extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) techniques, which are widely used to investigate local structure have also been applied to GaN films [45][46][47][48][49][50][51][52][53][54], although mostly for the fingerprinting of cubic and hexagonal symmetries and for exploring the coexistence of polytypes in mixed phase GaN [45,46]. There are also some reports on the investigation of the nature of point defects arising from Ar + bombardment and low energy ion implantation of MBE and MOCVD grown GaN films [47][48][49][50]. Near-edge x-ray absorption fine structure (NEXAFS) [47][48][49][50] studies at N K-edge have shown that ion implantation/bombardment of GaN films results in compositional changes and enhances microstructural distortion, which is evidenced by the presence of extra component peaks on the lower energy side, attributed to N interstitials and N antisites.…”

X-Ray Absorption Spectroscopy of Semiconductors

“…3.15 for 6H-SiC implanted at 77 K with Na ions at fluences ranging two orders of magnitude. Chemical effects have been also observed in GaN heavily implanted with Si, where the formation of Si-N bonds has been detected in [89]. In SiC both the Si and C atoms are tetrahedrally coordinated.…”

Influence of Si doping on size of GaN quantum dots grown by molecular beam epitaxy under Ga‐rich conditions

“…These frequency shifts may indicate the increasing length of Ga-N bonds in GaN wetting layer. In the case of bulk GaN film [9], high dose Si implantation causes the formation of Si-N bonds and defects in GaN. In addition, introduction of Si resulted in expansion of Ga-N bonds because the Ga-N bonds around the defect were pulled in the direction of the defect site.…”