Electronic stopping dependence of ion beam induced modifications in GaN (original) (raw)
Related papers
Effect of swift heavy ions of silver and oxygen on GaN
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006
Gallium nitride semiconductors are in the focus of current research. Investigative studies have been carried out to understand the effect of swift heavy ions on metal organic chemical vapour deposition (MOCVD) grown GaN epilayers. Silver (Ag8+) and oxygen (O7+) ions at energy of 100 MeV and fluence of 1 × 1013 ions cm−2 were used in this study. Irradiated samples were characterized by atomic force microscopy (AFM), photoluminescence (PL) and UV–Visible optical absorption. Surface defects were observed from AFM images, which indicate increase in defects after Ag8+ ion irradiation when compared to as-grown GaN. However, with O7+ ion irradiation there is decrease in the surface defects and smoothening of the surface. The PL studies show that O7+ ion irradiation gives rise to red shift and the optical absorption studies provide evidence for the change in the band gap after ion irradiation.
Journal of Physics D: Applied Physics, 2017
An investigation of mechanisms of enhancement of irradiation-induced damage formation in GaN under molecular in comparison to monatomic ion bombardment is presented. Ionimplantation-induced effects in wurtzite GaN bombarded with 0.6 keV/amu F, P, PF2, and PF4 ions at room temperature are studied experimentally and by cumulative MD simulation in the correct irradiation conditions. In the low dose regime, damage formation is correlated with a reduction in photoluminescence decay time, whereas in the high dose regime, it is associated with the thickness of the amorphous layer formed at the sample surface. In all the cases studied, a switch to molecular ion irradiation from bombardment by its monatomic constituents enhances the damage accumulation rate. Implantation of heavy Ag ion, having approximately the same mass as the PF4 molecule, is less effective in surface damage formation, but leads to noticeably higher damage accumulation in the bulk.. The cumulative MD simulations do not reveal any significant difference in the total amount of both point defects and small defect clusters produced by light monatomic and molecular ions. On the other hand, increased production of large defect clusters by molecular PF4 ions is clearly seen in the vicinity of the surface. Ag ions produce almost the same number of small, but more large defect clusters compare to the others. This findings show that the enhancement of stable damage formation in GaN under molecular, as well as under heavy monatomic ion irradiation, can be related to the higher formation probabilityof large defect clusters.
2007
Epitaxial GaN layers grown by MOCVD on c-plane sapphire substrates are irradiated with 150 MeV Ag ions at a fluence of 5 · 10 12 ions/cm 2 . Samples used in this study are 2 lm thick GaN layers, with and without a thin AlN cap-layer. Surface morphology is studied using contact mode atomic force microscopy (AFM). Irradiated samples show qualitatively different morphologies as well as quantitative changes. Different kinds of morphology are attributed to specific type of dislocations using the existing models available in the literature. The residual strain and sample quality have been analysed before and after irradiation using high resolution X-ray diffraction (HRXRD). The Lorentzian shape analyses of the experimental scans complement the AFM results. Optical properties are studied by spectrophotometer used in the transmission mode. A sharp band-edge in the as grown samples was observed at $3.4 eV. The band-edge absorption broadened due to irradiation and these results have been discussed in view of the damage created by the incident ions which compliment HRXRD results. In general the effect of irradiation induced-damages are analysed as a function of material properties. A possible mechanism responsible for the observations has been discussed.
Mechanisms of ion-induced GaN thin layer splitting
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009
The underlying physics and the role of H-defect interaction in H ion-induced splitting of GaN were investigated by transmission electron microscopy, high resolution X-ray diffraction, positron annihilation spectroscopy, ion channeling, elastic recoil detection, and infrared spectroscopy. A high concentration of void-like nanoscopic structures, nanobubbles, is detected immediately after implantation. Positron annihilation measurements demonstrate that the detected structures are vacancy clusters. FTIR data show that H-defect vibrational spectrum peaks at 3141 cm À1 mode attributed to V Ga -H 4 . A large fraction of H was found to be trapped in higher frequency modes which we associate tentatively to N-H stretch modes in the internal surfaces of nanobubbles. These nanobubbles persist during annealing up to 450°C. An increase of the strain is observed in this temperature range. This strain relaxes partially above 450°C following the formation of the platelets which are embryos of the microcracks.
MRS Proceedings, 2011
We report here swift heavy ion (SHI) irradiation induced effects on structural and surface properties of III-nitrides. Tensile strained Al (1-x) In x N/GaN Hetero-Structures (HS) were realized using Metal Organic Chemical Vapour Despotion (MOCVD) technique with indium composition as 12%. Ion species and energies are chosen such that electronic energy deposition rates differ significantly in Al (1-x) In x N and are essential for understanding the ion beam interactions at the interfaces. Thus the samples were irradiated with 80 MeV Ni 6+ and 100 MeV Ag 7+ ions at varied fluence (1×10 12 and 3 ×10 12 ions/cm 2 ) to alter the structural properties. Under this energy regime, the structural changes in Al (1-x) In x N would occur due to the intense ultrafast excitations of electrons along the ion path. We employed different characterization techniques like High Resolution X-ray Diffraction (HRXRD) and Rutherford back scattering spectrometry (RBS) for composition, thickness and strain. HRXRD and RBS experimental spectra have been fitted with Philip's epitaxy SIMNRA code, which yields thickness and composition from compound semiconductors. The surface morphology of pristine and irradiated samples is studied and compared by Atomic Force Microscopy (AFM).
Defect formation in GaN epitaxial layers due to swift heavy ion irradiation
Radiation Effects and Defects in Solids, 2011
GaN epitaxial layers were irradiated with 200 MeV Ag ions at various fluences. These samples were characterized ex situ by resistivity/Hall, XRD, and transmission electron microscopy (TEM). The resistivity of irradiated layers increased by eight orders of magnitude after irradiation with a fluence of 5 × 10 12 ions/cm 2 . The increase in peak width (FWHM) with the incident ion fluence showed a reduction in the crystallinity of epitaxial layers. Cross-sectional TEM images confirmed that at the highest fluence (5 × 10 12 ions/cm 2 ), electronic energy loss caused structural defect formation in the GaN layer.
Cu IONS IRRADIATION IMPACT ON STRUCTURAL AND OPTICAL PROPERTIES OF GaN THIN FILM
International Journal of Modern Physics B, 2013
Epitaxial grown Gallium nitride (GaN) thin film on sapphire was irradiated with Cu 23 ions at various fluences (5 × 10 14 , 1 × 10 15 and 5 × 10 15 cm −2 ). The level of lattice disorder, as measured by Rutherford backscattering spectrometry and channeling (RBS/C), 25 gradually increases with the increasing of ions fluence. Lattice amorphization is observed for the sample irradiated with fluence of 5 × 10 15 cm −2 which is also confirmed by X-27 ray diffractometer (XRD) analysis. It was found that both Raman modes of GaN layer clearly shifted with Cu + fluences. Both Raman and X-ray analyses explore that Cu 29 atom substituted into Ga sites. Atomic force microscopy (AFM) images show the irradiated GaN surface roughness increases with the increasing ions fluence. The UV-visible 31 transmittance spectrum and ellipsometric measurements show a decrease in the band gap value after irradiation of Cu ions in the GaN film. Moreover, the optical constants 33 (n and k) of the films vary with the increasing of Cu ion fluences.
Oxygen ion irradiation on AlGaN/GaN heterostructure grown on silicon substrate by MOCVD method
2015
In the present work, we have reported 100 MeV O 7+ ion irradiation with 1x10 12 and 5x10 12 ions/cm 2 fluence on AlGaN/GaN heterostructures grown on silicon substrate by Metal Organic Chemical Vapour Deposition (MOCVD). The Irradiated samples were characterized by High Resolution X-Ray Diffraction (HRXRD), Atomic Force Microscope (AFM) and Photoluminescence (PL). Crystalline quality has been analysed before and after irradiation using HRXRD. Different kinds of morphology are attributed to specific type of dislocations using the existing models available in the literature. A sharp band-edge emission in the as grown samples was observed at ~3.4 eV in GaN and 3.82 for AlGaN. The band-edge absorption intensity reduced due to irradiation and these results have been discussed in view of the damage created by the incident ions. In general the effect of irradiation induced-damages were analysed as a function of material properties. A possible mechanism responsible for the observations has been discussed.