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Journal ArticleDOI

Composition, structure and morphology of Al1−xInxN thin films grown on Al1−yGayN templates with different GaN contents

TL;DR: In this paper, four nominally Al0.85In0.15N thin films with different strains were grown simultaneously on Al1−yGayN (y = 1, 0.93, 087 and 0.69) templates by metal organic chemical vapour deposition, and the nominal InN content of ~15% was chosen to achieve close lattice matching of Al 1−xInxN with the templates of intermediate GaN molar fractions.
Abstract: Four nominally Al0.85In0.15N thin films with different strains were grown simultaneously on Al1−yGayN (y = 1, 0.93, 0.87 and 0.69) templates by metal organic chemical vapour deposition. The nominal InN content of ~15% was chosen to achieve close lattice matching of Al1−xInxN with the templates of intermediate GaN molar fractions, a small tensile strain for growth on GaN, and compressive strain for the template with the lowest GaN fraction. The film deposited on GaN reveals the highest structural quality, the lowest surface roughness and a homogeneous composition with depth. For growth on the Al1−yGayN ternary templates, the film roughness and the surface pit density both increase with decreasing GaN content, in line with the roughening of the growth templates themselves. Detailed study indicates that the structural and morphological qualities of the templates influence not only the quality of the Al1−xInxN films but also their composition profile. Results suggest that surface roughness of the template and growth on the inclined facets lead to compositional gradients due to a decreased InN incorporation on these facets and to the formation of V-pits.

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Citations
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TL;DR: In this article, a simple strain model is proposed to explain the unusual behavior of impurity formation energy in semiconductor systems and suggest that strain could be used to improve the doping solubility in semiconductors.
Abstract: When a semiconductor host is doped by a foreign element, it is inevitable that a volume change will occur in the doped system. This volume change depends on both the size and charge state difference between the dopant and the host element. Unlike the "common expectation" that if the host is deformed to the same size as the dopant, then the formation energy of the dopant would reach a minimum, our first-principles calculations discovered that when an external hydrostatic strain is applied, the change of the impurity formation energy is monotonic: it decreases if the external hydrostatic strain is applied in the same direction as the volume change. This effect also exists when a biaxial strain is applied. A simple strain model is proposed to explain this unusual behavior, and we suggest that strain could be used to significantly improve the doping solubility in semiconductor systems.

68 citations

Journal ArticleDOI
TL;DR: InxAl1−−xN films with composition 0.25 and 0.86 were grown on p-type Si (111) substrates by using reactive magnetron co-sputtering technique in an ambient of argon and nitrogen at 200°C as mentioned in this paper.

17 citations

Journal ArticleDOI
TL;DR: In this paper, the lattice parameters of the alloys generally obey Vegard's rule, varying linearly with the InN fraction, within the limits of experimental accuracy, and in the compositional range 0.08 to 0.28, and this is consistent with the small deviation from linear behaviour suggested by Darakchieva et al.
Abstract: In this work, comparative x-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) measurements allow a comprehensive characterization of Al1−x In x N thin films grown on GaN. Within the limits of experimental accuracy, and in the compositional range 0.08 < x < 0.28, the lattice parameters of the alloys generally obey Vegard's rule, varying linearly with the InN fraction. Results are also consistent with the small deviation from linear behaviour suggested by Darakchieva et al (2008 Appl. Phys. Lett. 93 261908). However, unintentional incorporation of Ga, revealed by atom probe tomography (APT) at levels below the detection limit for RBS, may also affect the lattice parameters. Furthermore, in certain samples the compositions determined by XRD and RBS differ significantly. This fact, which was interpreted in earlier publications as an indication of a deviation from Vegard's rule, may rather be ascribed to the influence of defects or impurities on the lattice parameters of the alloy. The wide-ranging set of Al1−x In x N films studied allowed furthermore a detailed investigation of the composition leading to lattice-matching of Al1−x In x N/GaN bilayers.

12 citations

Journal ArticleDOI
TL;DR: In this paper, a detailed spectroscopic analysis of NIR emission of the thulium implanted and annealed AlxGa1-xN layers is presented by using temperature dependent steady-state PL, room temperature PL excitation, and time resolved PL.
Abstract: AlxGa1-xN samples, with different AlN molar fractions, x = 0, 0.15, 0.77, and 1, grown by halide vapor phase epitaxy were implanted with Tm ions. Photoluminescence (PL) measurements revealed that after thermal annealing all the samples exhibit intraionic Tm3+ luminescence. In samples with x > 0, the low temperature emission is dominated by the lines that appear in the near infrared (NIR) spectral region, corresponding to the overlapped 1G4 → 3H5 and 3H4 → 3H6 multiplet transitions. A detailed spectroscopic analysis of NIR emission of the thulium implanted and annealed AlxGa1-xN layers is presented by using temperature dependent steady-state PL, room temperature PL excitation, and time resolved PL. The results indicate that the excitonic features sensitive to the alloy disorder are involved in the excitation population processes of the Tm3+ luminescence and the highest thermal stability for the NIR emission occurs for the AlN:Tm sample.

7 citations

Journal ArticleDOI
TL;DR: In this paper, a layer deconvolution Williamson-Hall (WH) plot analysis was proposed to estimate the peak broadening of a single crystal by deconvoluting the total crystal size into a finite number of layers, each with a constant thickness, strain and mosaic spread.
Abstract: The application of conventional Williamson–Hall (WH) plot analysis to crystals often results in broadening not proportional to the scattering length vector Several reasons may influence the broadening such as composition or strain heterogeneities, wafer curvature, dislocation anisotropy and other defects In this work, linearization of WH plots is achieved given the assumption that the total crystal size may be deconvoluted into a finite number of layers, each with a constant thickness, strain and mosaic spread A novel linearization algorithm, the layer deconvolution WH (LdCWH) method, employs a finite number of pseudo-Voigt (PV) functions for each measurement Afterwards, it searches for possible solutions by changing the PV coefficients until r2 of the conventional WH representation is above 0999 The searching procedure consists in a combination of a genetic algorithm (GA) to generate randomly the PV coefficients within a specified range and a Marquardt–Levenberg algorithm to fit simultaneously the measured reflections using the PV coefficients as inputs The possible solutions further allow estimating the upper and lower bounds of the mosaicity Conventional WH plots and the implementation of the LdCWH are applied to a commercial AlGaN thick layer and to bulk α-MoO3 crystals and discussed For the former, the lateral and perpendicular coherence lengths, tilt angle and heterogeneous strain derived are 616 ± 7 nm, 510 ± 10 nm, 0069 ± 0001° and 00345 ± 00002%, respectively, while for the latter, a vertical coherence length of 3883 ± 56 nm and heterogeneous strain of 00556 ± 00002% are found The nature of peak broadening regarding integral breadth and full width at half-maximum is discussed

4 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III-V semiconductors that have been investigated to date is presented.
Abstract: We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

2,525 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the stress associated with crystallite coalescence during the initial stages of growth in thin polycrystalline films with island growth morphology and predicted large tensile stresses in agreement with experimental results.
Abstract: We examined the stress associated with crystallite coalescence during the initial stages of growth in thin polycrystalline films with island growth morphology. As growing crystallites contacted each other at their bases, the side-walls zipped together until a balance was reached between the energy associated with eliminating surface area, creating a grain boundary and straining the film. Our estimate for the resulting strain depends only on interfacial free energies, elastic properties, and grain size and predicts large tensile stresses in agreement with experimental results. We also discuss possible stress relaxation mechanisms that can occur during film growth subsequent to the coalescence event.

554 citations

Journal ArticleDOI
TL;DR: In this paper, the structural and optical properties of lattice-matching AlInN layers to GaN have been investigated and their specific use to realize nearly strain-free structures for photonic and electronic applications has been discussed.
Abstract: We report on the current properties of Al1-x InxN (x approximate to 0.18) layers lattice- matched ( LM) to GaN and their specific use to realize nearly strain- free structures for photonic and electronic applications. Following a literature survey of the general properties of AlInN layers, structural and optical properties of thin state- of- the- art AlInN layers LM to GaN are described showing that despite improved structural properties these layers are still characterized by a typical background donor concentration of ( 1 - 5) x 10(18) cm(-3) and a large Stokes shift (similar to 800 meV) between luminescence and absorption edge. The use of these AlInN layers LM to GaN is then exemplified through the properties of GaN/ AlInN multiple quantum wells ( QWs) suitable for near- infrared intersubband applications. A built- in electric field of 3.64MVcm(-1) solely due to spontaneous polarization is deduced from photoluminescence measurements carried out on strain- free single QW heterostructures, a value in good agreement with that deduced from theoretical calculation. Other potentialities regarding optoelectronics are demonstrated through the successful realization of crack- free highly reflective AlInN/ GaN distributed Bragg reflectors ( R > 99%) and high quality factor microcavities ( Q > 2800) likely to be of high interest for short wavelength vertical light emitting devices and fundamental studies on the strong coupling regime between excitons and cavity photons. In this respect, room temperature ( RT) lasing of a LM AlInN/ GaN vertical cavity surface emitting laser under optical pumping is reported. A description of the selective lateral oxidation of AlInN layers for current confinement in nitride- based light emitting devices and the selective chemical etching of oxidized AlInN layers is also given. Finally, the characterization of LM AlInN/ GaN heterojunctions will reveal the potential of such a system for the fabrication of high electron mobility transistors through the report of a high two- dimensional electron gas sheet carrier density ( n(s) similar to 2.6 x 10(13) cm(-2)) combined with a RT mobility mu(e) similar to 1170 cm(2) V-1 s(-1) and a low sheet resistance, R similar to 210 Omega square.

313 citations

Journal ArticleDOI
TL;DR: In this article, room temperature electron mobility of 1170cm2∕Vs is obtained in an undoped, lattice-matched, Al0.82In0.18N∕GaN field effect transistor heterostructure.
Abstract: Room temperature electron mobility of 1170cm2∕Vs is obtained in an undoped, lattice-matched, Al0.82In0.18N∕GaN field-effect transistor heterostructure, while keeping a high (2.6±0.3)×1013cm−2 electron gas density intrinsic to the Al0.82In0.18N∕GaN material system. This results in a two-dimensional sheet resistance of 210Ω∕◻. The high mobility of these layers, grown by metal-organic vapor phase epitaxy on sapphire substrate, is obtained thanks to the insertion of an optimized AlN interlayer, reducing the alloy related interface roughness scattering.

311 citations