Structural Changes Induced by Swift Heavy Ion Beams in tensile strained Al (1-x)InxN /GaN Hetero-structures (original) (raw)
Related papers
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.
Strain effects in group-III nitrides: Deformation potentials for AlN, GaN, and InN
Applied Physics Letters, 2009
A systematic density functional theory study of strain effects on the electronic band structure of the group-III nitrides ͑AlN, GaN, and InN͒ is presented. To overcome the deficiencies of the local-density and generalized gradient approximations the Heyd-Scuseria-Ernzerhof ͑HSE͒ hybrid functional is used. Cross checks for GaN demonstrate good agreement between HSE and exact-exchange based G 0 W 0 calculations. We observe a pronounced nonlinear dependence of band-energy differences on strain. For realistic strain conditions in the linear regime around the experimental equilibrium volume a consistent and complete set of deformation potentials is derived.
Swift heavy ions effects in III–V nitrides
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2008
Four III-V nitrides, BN, AlN, GaN and InN have been irradiated under normal incidence at 300 K at GANIL (Caen, France) accelerator with 132 MeV 209 Pb 32+ swift heavy ions. Specimens were ion thinned for TEM observations before irradiation. Boron and aluminium nitrides were undamaged by the irradiation unlike the two others. In gallium and indium nitrides, ion impacts are found, forming circular areas. Their diameters are 3 and 8 nm, respectively. In fact, two regions may be distinguished around the ion impact: the inner part attributed to the section of the track formed along the ion path and corresponding to re-crystallized material and the external part to a strained material. For InN, structural defects, dislocations or interstitial loops are localised at the interface between the two regions and in the inner part.
Journal of Applied Physics, 2004
We have investigated compositional changes on GaN surfaces under low-energy Ar ion bombardment using synchrotron-based high-resolution core-level photoemission measurements and near-edge x-ray absorption fine-structure ͑NEXAFS͒ spectroscopy. The low-energy ion bombardment of GaN produces a Ga-rich surface layer which transforms into a metallic Ga layer at higher bombarding energies. At the same time, the photoemission spectra around the N 1s core level reveal the presence of both uncoordinated nitrogen and nitrogen interstitials, which we have analyzed in more detail by x-ray absorption measurements at the N K-edge. We have proposed a mechanism for the relocation and loss of nitrogen during ion bombardment, in agreement with some recent experimental and theoretical studies of defect formation in GaN. We have also demonstrated that photoemission spectroscopy and NEXAFS provide a powerful combination for studying compositional changes and the creation of point defects at GaN surface.
Ion beam studies of multi-quantum wells of III-nitrides
Vacuum, 2010
a b s t r a c t III-Nitrides have attracted much attention due to their versatile and wide range of applications, such as blue/UV light emitting diodes. Strained layer super lattices offer extra degree of freedom to alter the band gap of lattice-mismatched heterostructures. Swift heavy ion irradiation is a post-growth technique to alter the band gap of semiconductors, spatially. In the present study, strained AlGaN/GaN multi-quantum wells (MQWs) were grown on sapphire with insertion of AlN and GaN as buffer layers between substrate and epilayers. Such grown AlGaN/GaN MQWs, AlGaN/GaN heterostructures and GaN layers were irradiated with 200 MeV Au and 150 MeV Ag ions at a fluence of 5 Â 10 11 ions/cm 2 and 5 Â 10 12 ions/cm 2 respectively. As-grown and irradiated samples have been characterized by high resolution XRD, photoluminescence and RBS/channelling. Measured strain values show that strain increases upon irradiation and the luminescence properties are enhanced. RBS/channelling confirms the increase in strain values upon irradiation. In this paper we describe the effects of swift heavy ion irradiation on structural and optical properties.
Electronic stopping dependence of ion beam induced modifications in GaN
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2011
We report here Swift heavy ion induced effects in GaN samples grown by metal organic chemical vapor deposition (MOCVD) technique. These samples were irradiated with 80 MeV Ni and 100 MeV Ag ions at a fixed fluence of 1 Â 10 13 ions/cm 2 . Ion species and energies are chosen such that the difference in their electronic energy loss (S e ) would be 8 keV/nm. Effects of Ag on structural and optical properties over Ni ions have been discussed extensively. We employed different characterization techniques like High Resolution X-ray Diffraction (HRXRD) and Raman Spectroscopy for defect density calculations and for vibrational modes, respectively. Defect densities are calculated and compared using Williamson-Hall method from HRXRD. Change of strain and vibrational modes with S e has been discussed.