Single-crystal Al0.8 In0.2 N (0001) thin films were grown epitaxially onto lattice-matched Ti0.2 Zr0.8 N (111) seed layers on MgO(111) substrates at 300 °C by magnetron sputter epitaxy. Low-energy ion-assisted epitaxial growth conditions were achieved by applying a substrate potential of -15 V. Cross-sectional high-resolution electron microscopy verified the epitaxy and high-resolution x-ray diffraction ω -rocking scans of the Al0.8 In0.2 N 0002 peak (full width at half maximum ∼2400 arc sec) indicated a high structural quality of the films. Cathodoluminescence measurements performed in a scanning electron microscope at 5 K revealed Al0.8 In0.2 N luminescence at 248 nm, or equivalently 5.0 eV, showing that Al0.8 In0.2 N is a promising material for deep-ultraviolet optoelectronic devices. © 2006 American Institute of Physics.

InN to 6.2 eV for AlN, which opens possibilities to engineer opto-electronic devices operating from infra-red to deep ultra-violet wavelengths. Al_1-xIn_xN with the alloy composition x~0.2 can also be used as a lattice-matched electron confinement layer for GaN based electronic devices. However, the ternary Al_1-xIn_xN system exhibits a miscibility gap for compositions in the range 0.1<0.9 where a stable alloy cannot be grown under thermodynamic equilibrium conditions, which is why low temperature growth techniques such as magnetron sputtering are of advantage for their syntheses.

This thesis describes the growth and structural characterization of epitaxial 2h-Al_1-xIn_xN(0001) [0<1] thin films synthesized by dual DC reactive Magnetron Sputter Epitaxy (MSE) in an ultra-high vacuum (UHV) deposition system. Growth parameters such as deposition temperature, substrate bias, and magnetron power settings were adjusted in order to control the film stoichiometry and crystallinity. The role of in-situ deposited Ti_1-yZr_yN(111) [0£y£1] seed layers on the Al_1-xIn_xN growth was also investigated. It was found that the ZrN(111) seed layers provide a wider stoichiometric composition region for the wide band-gap nitride at elevated temperatures due to its generally lower lattice mismatch as compared to TiN(111). Microstructural characterization of Al_1-xIn_xN deposited at temperatures from room temperature to 900 °C was carried out by X-ray diffraction (XRD) techniques and transmission electron microscopy (TEM). TEM micrographs revealed a dense and columnar microstructure with column widths ranging from 10 to 200 nm depending on growth temperature and seed layer. In addition, a novel generic growth mode giving rise to extremely curved, though stress-free, crystal lattices was observed and investigated. It was found that these, so called, nano-grass structures arise due to specific kinetic and geometrical limitations during growth. Compositional differences are formed over the columns due to self-shadowing effects, which are partly preserved due to the low surface ad-atom mobility. Thus, extremely curved crystalline columns can be formed. XRD investigations showed thatsingle-phase wurtzite epitaxial Al_1-xIn_xN was obtainable throughout the whole composition range for deposition temperatures of up to 600 °C onto ZrN(111) seed layers. At higher temperatures almost pure hexagonal AlN was formed. XRD and selected area electron diffraction also showed that the Al_1-xIn_xN films were grown hetero-epitaxially onto Ti_1-yZr_yN with the epitaxial relationship: Al_1-xIn_xN(0001) // Ti_1-yZr_yN(111) and Al_1-xIn_xN[11-20] // Ti_1-yZr_yN[110]. Based on the results, pseudo-binary phase diagrams for MSE deposition of 2h-Al_1-xIn_xN, at temperatures up to 1000 °C, onto TiN(111) and ZrN(111) coated MgO(111) could be established.

A study on the relationship between the Al1-xInxN mole fraction x, in the range 0.07<0.82, and the lattice parameters was carried out for epitaxial Al_1-xIn_xN(0001)/ Ti_1-yZr_yN/MgO(111) films using Rutherford Backscattering Spectrometry (RBS) and XRD. A non-linear relationship was found with a maximum deviation as large as 37 % from the commonly used linear Vegard’s rule. The highest relative deviations were found at low InN mole fractions, while the largest absolute deviation was found at x=0.63. This shows that Vegard’s rule is not directly applicable to determine the compositions in the Al_1-xIn_xN system.

Moreover, the post-growth thermal stability of the Al_1-xIn_xN films was investigated by in-situ annealing in an X-ray diffractometer during extensive time periods at temperatures up to 1300 °C. It was found that the thermal stability of the Al1-xInxN films increased with a decreasing In content. Al_0.87In_0.13N deposited onto ZrN(111) at 300 °C showed to be stable up to 1050 °C, which is about the growth temperature used for GaN in HVPE, thus showing that Al1-xInxN can be used as a template for lattice-matched growth of GaN devices.

An optimized growth process for Al_0.8In_0.2N(0001) onto lattice matched seed layers of T_i0.2Zr_0.8N(111) was developed. A mild ion assistance together with a low deposition temperature was found to give the best over-all epi-layer quality. Full-width-at-halfmaximum (FWHM) values of ~40 arc min. was obtained in XRD rocking mode. Furthermore, luminescence at wavelengths as short as 248 nm was observed in these epilayers by cathodoluminescence (CL) measurements performed at 5 K. The corresponding energy of 5.0 eV is the highest reported to date for Al_0.8In_0.2N.

In summary, these results point on the feasibility of metastable Al0.8In0.2N solid solutions as an active luminous material in opto-electronics. It also shows that MSE-grown Al_1-xIn_xN has a high band gap, which make it an excellent choice as a strong charge carrier confinement epi-layer in lattice matched GaN or In_1-zGa_zN hetero-structures.

Hydrogen incorporation is shown to cause passivation of various N-related localized states and partial neutralization of N-induced changes in the electronic structure of the GaNxP1-x alloys with x < 0.008. According to the performed X-ray diffraction measurements, the hydrogenation is also found to cause strong expansion of the GaNP lattice which even changes from a tensile strain in the as-grown GaNP epilayers to a compressive strain in the post-hydrogenated structures with the highest H concentration. By comparing results obtained using two types of hydrogen treatments, i.e. by implantation from a Kaufman source and by using a remote dc H plasma, the observed changes are shown to be inherent to H due to its efficient complexing with N atoms, whereas possible effects of implantation damage are only marginal. (c) 2005 Elsevier B.V. All rights reserved.

A materials structure is reported that is characterized by high lattice curvature assigned to a compositional gradient. The phenomenon occurs for physical vapour deposition of Al1-xInxN epitaxial thin films with directional fluxes of Al and In at kinetically limited growth conditions. According to our growth model unit cells are incorporated on the growth surfaces of emerging whiskers (nanowires) with a continuously varying lattice parameter depending on their position with respect to Al- and In-rich sides of the whisker. Such curved crystals are effectively quenched solid solutions. We present a description of this generic, self-assembled curved crystal structure and its implications. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ternary wurtzite Al1-x Inx N thin films with compositions throughout the miscibility gap have been grown onto seed layers of TiN and ZrN by magnetron sputter epitaxy (MSE) using dual reactive direct current magnetron sputter deposition under ultra high vacuum conditions. The film compositions were calculated using Vegard's law from lattice parameters determined by x-ray diffraction (XRD). XRD showed that single-phase Al1-x Inx N alloy films in the wurtzite structure with [0.10<x<0.90] could be obtained at substrate temperatures up to 600°C by heteroepitaxial growth. Epitaxial growth at 600°C gave the crystallographic relations Al1-x Inx N (0001) TiN,ZrN (111) and Al1-x Inx N <10-10> TiN,ZrN <110>. At higher substrate temperatures almost pure AlN was formed. The microstructure of the films was also investigated by high-resolution electron microscopy. A columnar growth mode with epitaxial column widths from 10 to 200 nm was observed. Rocking curve full-width-at-half-maximum measurements revealed highly stressed lattices for growth onto TiN at 600°C. Pseudobinary MSE growth phase field diagrams for Al1-x Inx N onto ZrN and TiN were established for substrate temperatures up to 1000°C. Large regimes for single-phase solid solutions were thus identified with In being the diffusing species. © 2005 American Institute of Physics.

This thesis describes the growth and structural characterization of epitaxial 2h­ A1_1-xIn_xN ranging from pure A1N to InN [0<x<1]. Thin A1_1-xIn_xN films were synthesized by dual DC reactive Magnetron Sputter Epitaxy (MSE) in an ultra-high vacuum (UHV) system. Growth parameters such as deposition temperature and magnetron power settings were adjusted in order to control the film stoichiometry. The role of in-situ deposited TiN(111) and ZrN(111) seed layers on the A1_1-xIn_xN growth was also investigated. It was found that ZrN(111) seed layers provide a wider stoichiometric composition region at elevated temperatures due to its low lattice mismatch as compared to TiN(111). Microstructural characterization of A1_1-xIn_xN deposited at temperatures from 300 to 900 °C was carried out by X-ray diffraction (XRD) techniques and transmission electron microscopy (TEM). TEM micrographs revealed a dense and columnar microstructure with column widths ranging from 10 to 200 nm depending on growth temperature and seed layer. In addition, a novel generic growth mode giving rise to extremely curved, though stress- free, crystal lattices was observed and investigated. It was found that these, so called, nano-grass structures arise due to specific kinetic and geometrical limitations during growth. Compositional differences are formed over the columns due to self-shadowing effects, which are partly preserved due to the low surface ad-atom mobility. Thus resulting in extremely curved crystalline columns. XRD investigations showed that single-phase wurtzite epitaxial A1_1-xIn_xN was obtainable throughout the whole composition range for deposition temperatures of up to 600 °C onto ZrN(111) seed layers. At higher temperatures almost pure hexagonal A1N was formed. XRD and selected area electron diffraction also showed that the A1_1-xIn_xN films were grown hetero-epitaxially onto TiN and ZrN with the epitaxial relationship: A1_1-xIn_xN(0001)//TiN(ZrN)(111) and A1_1-xIn_xN[10-10]//TiN(ZrN)[110]. In the case of A1_1-xIn_xN depositions onto TiN(111) seed layers, a phase separation of A1_1-xIn_xN was observed when mid-x compositions was targeted at deposition temperatures of 600 °C. This observation was confirmed by TEM results, which revealed a layered structure with epitaxial 2h-A1_1-xIn_xN followed by a nano-crystalline structure. Based on the results, pseudo-binary phase diagrams for MSE deposition of 2h-A1_1-xIn_xN, at temperatures up to 1000°C, onto TiN(111) and ZrN(111) coated MgO(111) could be established.

Ternary Al1-xInxN thin films were grown by dual target direct current (DC) reactive magnetron sputtering under UHV conditions. The film compositions were determined to range from 0.30

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(SiC)(X)(AIN)(1-X) thin films have been grown epitaxially on vicinal 6H-SiC (0001) by low-energy ion assisted dual magnetron sputtering in UHV conditions. AES showed a decreasing Si and C content for an increasing magnetron power ratio, (P-Al/P-SiC). The epitaxial quality of the films was improved as the SiC fraction increased. Films containing less than 5% of Si and C show an evolution of domain width similar to the growth of pure AIN. HRXRD show a decreased c-axis lattice parameter for a film with composition of AINC(X) (0less than or equal toxless than or equal to0.1), indicating carbon substitution in AIN. CL spectra show defect-related peaks of similar to3.87 and similar to4.70 eV, corresponding to O and C impurities respectively as well as on un-identified peak at similar to3.40 eV.

[No abstract available]