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10 Jan 2005

Volume 86, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 86, 021101 (2005); http://dx.doi.org/10.1063/1.1849439 (3 pages)

H. W. Choi, C. W. Jeon, C. Liu, I. M. Watson, M. D. Dawson, P. R. Edwards, R. W. Martin, S. Tripathy, and S. J. Chua
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Combination of time of flight direct recoiled spectroscopy and ion scattering trajectory simulations of (Ga,Mn)N growth by chemical beam epitaxy

Luz Angela Carreño and Abdelhak Bensaoula

Appl. Phys. Lett. 86, 021901 (2005); http://dx.doi.org/10.1063/1.1841478 (3 pages)

Online Publication Date: 30 December 2004

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In situ direct recoiled spectroscopy combined with scattering-recoiling trajectory simulations were applied to characterization of (Ga,Mn)N thin films grown by chemical beam epitaxy. Relative intensities of the scattering and recoiling signals recorded as a function of the sample azimuthal rotation allowed determination of the surface composition and periodicity. Models locating the Mn atoms at Ga sites and interstitial positions and the presence of N vacancies at percent levels were simulated. We find that most Mn atoms are located at Ga sites with a nonnegligible level going to interstitial positions; inclusion of N vacancies is also necessary to duplicate some experimental features. This agrees with the samples free carrier concentrations and photoluminescence measurements.
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68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.55.A- Nucleation and growth
81.05.Hd Other semiconductors
68.55.Nq Composition and phase identification
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.J- Point defects and defect clusters
68.35.Dv Composition, segregation; defects and impurities
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.S- Impurities in crystals
75.50.Pp Magnetic semiconductors

Lowered dislocation densities in uniform GaN layers grown on step-free (0001) 4H-SiC mesa surfaces

N. D. Bassim, M. E. Twigg, C. R. Eddy, J. C. Culbertson, M. A. Mastro, R. L. Henry, R. T. Holm, P. G. Neudeck, A. J. Trunek, and J. A. Powell

Appl. Phys. Lett. 86, 021902 (2005); http://dx.doi.org/10.1063/1.1849834 (3 pages) | Cited 6 times

Online Publication Date: 3 January 2005

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We report that very low threading dislocation densities (8×107/cm2) were achieved in uniform GaN layers grown by metalorganic chemical vapor deposition on (0001) 4H-SiC mesa surfaces 50 μm×50 μm in area that were completely free of steps. Transmission electron microscopy (TEM) indicated that all observable GaN film threading dislocations were of edge type. TEM analysis of the defect structure of the nucleation layer (aluminum nitride, AlN) revealed a lack of c-component dislocations, and the clean annihilation of lateral, a-type dislocations within the first 200 nm of growth, with no lateral dislocations developing threading arms. These results indicate that the elimination of steps on the initial (0001) 4H-SiC growth surface may play an important role in the removal of mixed and c-type dislocations in subsequently grown AlN and GaN heteroepitaxial layers.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Lp Transmission electron microscopy (TEM)

Effect of Cu deficiency on the defect levels of Cu0.86In1.09Se2.05 determined by spectroscopic ellipsometry

Sung-Ho Han, Falah S. Hasoon, Hamda A. Al-Thani, Allen M. Hermann, and Dean H. Levi

Appl. Phys. Lett. 86, 021903 (2005); http://dx.doi.org/10.1063/1.1849840 (3 pages) | Cited 4 times

Online Publication Date: 3 January 2005

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Room temperature spectroscopic ellipsometry measurement of Cu0.86In1.09Se2.05 reveals that shallow defect states are found in the sub-band-gap region. The energies of these defect levels are in quantitative agreement with those calculated and measured by photoluminescence, electrical conductivity, optical absorption, and deep level transient spectroscopy at low temperatures. The results can be explained in terms of the defect physics of this material and suggest that the defect levels are due to Cu deficiency. This work opens up the possibility of measuring defect levels of off-stoichiometric or heavily doped semiconductors by spectroscopic ellipsometry at room temperature.
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71.55.Ht Other nonmetals
78.66.Li Other semiconductors

Enhanced terahertz emission from porous InP (111) membranes

M. Reid, I. V. Cravetchi, R. Fedosejevs, I. M. Tiginyanu, and L. Sirbu

Appl. Phys. Lett. 86, 021904 (2005); http://dx.doi.org/10.1063/1.1849813 (3 pages) | Cited 12 times

Online Publication Date: 3 January 2005

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Bulk n-InP wafers and porous membrances with (111) crystallographic orientation have been illuminated with 120 fs pulses of 800 nm radiation from a Ti:Sapphire amplified laser system. Terahertz (THz) emission from samples was measured as a function of excitation fluence in the reflection geometry. It was established that the THz emission from both bulk and porous InP (111) saturates at high excitation fluence, emitting comparable levels of far-infrared radiation. Below saturation, however, the emission from the porous InP (111) membrane was found to be approximately an order of magnitude greater in radiated electric field or approximately two orders of magnitude in power relative to the bulk sample. The observed increase in efficiency from the porous, relative to the bulk samples, can be attributed either to the local field enhancement in the porous network for the nonlinear contribution to the radiated THz fields, or to modifications of the transient currents resulting in enhanced THz radiation.
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78.70.Gq Microwave and radio-frequency interactions
78.47.-p Spectroscopy of solid state dynamics

Structure of the carrot defect in 4H-SiC epitaxial layers

M. Benamara, X. Zhang, M. Skowronski, P. Ruterana, G. Nouet, J. J. Sumakeris, M. J. Paisley, and M. J. O’Loughlin

Appl. Phys. Lett. 86, 021905 (2005); http://dx.doi.org/10.1063/1.1849416 (3 pages) | Cited 18 times

Online Publication Date: 4 January 2005

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Transmission electron microscopy and KOH etching were used to determine the structure of the carrot defect in 4H-SiC epilayers. The defect consists of two intersecting planar faults on prismatic {1math00} and basal {0001} planes. Both faults are connected by a stair-rod dislocation with Burgers vector 1/n [10math0] with n>3 at the crossover. A Frank-partial dislocation with b = 1/12[4math03] terminates the basal fault.
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61.72.Nn Stacking faults and other planar or extended defects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Formation of binary phase gratings in photopolymer-liquid crystal composites by a surface-controlled anisotropic phase separation

Jae-Hong Park, Iam Choon Khoo, Chang-Jae Yu, Min-Sik Jung, and Sin-Doo Lee

Appl. Phys. Lett. 86, 021906 (2005); http://dx.doi.org/10.1063/1.1851008 (3 pages) | Cited 8 times

Online Publication Date: 4 January 2005

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We report on formation of binary phase gratings in photopolymer-liquid crystal (PLC) composites using a surface-controlled phase separation method. The binary nature of the PLC phase gratings is produced by employing a single step photo-ablation through an amplitude photomask which precisely controls the interfacial interactions between the LC and the photopolymer on the alignment layer. A subsequent illumination of the ultraviolet light onto the whole PLC promotes an anisotropic phase separation resulting in the formation of distinct binary patterns for the PLC structure. The electrically tunable diffraction properties of the binary phase gratings are presented.
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42.70.Df Liquid crystals
42.70.Jk Polymers and organics
42.79.Dj Gratings
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
42.82.Cr Fabrication techniques; lithography, pattern transfer
61.82.Pv Polymers, organic compounds

Reversible change of birefringence sign by optical and thermal processes in an azobenzene polymethacrylate

F. J. Rodríguez, C. Sánchez, B. Villacampa, R. Alcalá, R. Cases, M. Millaruelo, and L. Oriol

Appl. Phys. Lett. 86, 021907 (2005); http://dx.doi.org/10.1063/1.1851012 (3 pages) | Cited 5 times

Online Publication Date: 4 January 2005

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Birefringence (Δn) induced in an azobenzene polymethacrylate by combination of biphotonic and thermotropic processes has subsequently been changed in sign by room temperature illumination with linearly polarized blue light. The sign of Δn can be reversed again, by simply heating up the film to 100 °C. This change of Δn between positive and negative values can be repeated several times. Besides, by appropriate choice of film thickness and blue light irradiation conditions the same absolute value for positive and negative Δn values can be obtained.
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42.70.Jk Polymers and organics
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
78.20.Fm Birefringence
61.82.Pv Polymers, organic compounds
78.66.Qn Polymers; organic compounds
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.40.Gh Other heat and thermomechanical treatments

Luminescence from stacking faults in gallium nitride

R. Liu, A. Bell, F. A. Ponce, C. Q. Chen, J. W. Yang, and M. A. Khan

Appl. Phys. Lett. 86, 021908 (2005); http://dx.doi.org/10.1063/1.1852085 (3 pages) | Cited 124 times

Online Publication Date: 4 January 2005

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A direct correlation has been established between stacking faults in a-plane GaN epilayers and luminescence peaks in the 3.29–3.41 eV range. The structural features of the stacking faults were determined by diffraction-contrast transmission electron microscopy, while the optical emission characteristics were observed by highly spatially resolved monochromatic cathodoluminescence. The studies were performed in the exact same regions of thinned foils. We find that stacking faults on the basal plane are responsible for the strong emission at ∼ 3.14 eV. Luminescence peaks at ∼ 3.33 and ∼ 3.29 eV are associated with the presence of stacking faults on prismatic a planes and partial dislocations at the stacking fault boundaries, respectively.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
61.72.Nn Stacking faults and other planar or extended defects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)

Femtosecond transient fluorescence spectrometer based on parametric amplification

Piotr Fita, Yuriy Stepanenko, and Czeslaw Radzewicz

Appl. Phys. Lett. 86, 021909 (2005); http://dx.doi.org/10.1063/1.1850591 (3 pages) | Cited 15 times

Online Publication Date: 4 January 2005

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We report an experimental proof-of-principle of a method for recording femtosecond, time-resolved fluorescence spectra in the visible range. The method is based on a noncollinear parametric amplification in a beta barium borate crystal and provides time resolution of the order of 100 fs. We demonstrate that with this method, transient fluorescence spectra as wide as 6000 cm−1 can be recorded in a single time-delay scan. Fluorescence decay dynamics and transient spectra of Coumarin 6 dye dissolved in aniline were measured to test the usefulness of the method.
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07.60.Rd Visible and ultraviolet spectrometers
78.47.-p Spectroscopy of solid state dynamics
78.55.Hx Other solid inorganic materials
78.45.+h Stimulated emission

Einstein oscillator in highly-random-packed bulk metallic glass

M. B. Tang, H. Y. Bai, M. X. Pan, D. Q. Zhao, and W. H. Wang

Appl. Phys. Lett. 86, 021910 (2005); http://dx.doi.org/10.1063/1.1849420 (3 pages) | Cited 10 times

Online Publication Date: 5 January 2005

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Metallic glasses have often been regarded as ideal model systems of dense random packing with strong interaction among their components. Here we report direct evidence for the presence of the Einstein oscillator with an Einstein temperature θE of 74 K, which induces the boson peak at 4.9 meV in bulk metallic glass Zr46.75Ti8.25Cu7.5Ni10Be27.5. The presence of an Einstein oscillator suggests the existence of the vibrations of loose atoms in an independent localized harmonic mode in the highly random packed metallic glasses.
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63.50.-x Vibrational states in disordered systems
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.

Direct evidence of nanocluster-induced luminescence in InGaN epifilms

H. J. Chang, C. H. Chen, Y. F. Chen, T. Y. Lin, L. C. Chen, K. H. Chen, and Z. H. Lan

Appl. Phys. Lett. 86, 021911 (2005); http://dx.doi.org/10.1063/1.1843279 (3 pages) | Cited 11 times

Online Publication Date: 5 January 2005

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x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectrometry, and cathodoluminescence measurements have been employed to study the correlation between optical and structural properties in InGaN epitaxial films. In-rich quantum dots were found to be dispersed throughout the film. By the combination of these measurements, we clearly identify that brighter luminescence arises from In-rich regions while dimmer luminescence corresponds to the Ga-rich matrix regions.
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68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Reduction of the threading dislocation density in GaN films grown on vicinal sapphire (0001) substrates

X. Q. Shen, H. Matsuhata, and H. Okumura

Appl. Phys. Lett. 86, 021912 (2005); http://dx.doi.org/10.1063/1.1849836 (3 pages) | Cited 26 times

Online Publication Date: 5 January 2005

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Structural properties of GaN films grown on vicinal sapphire (0001) substrates with various vicinal angles by plasma-assisted molecular beam epitaxy are investigated. High-resolution x-ray diffraction (HRXRD) results reveal the dramatic improvement of both tilting and twisting grain features of the GaN films when the vicinal angle is larger than 0.5° with the formation of multilayer macro-steps on the surface. The threading dislocation density reduces by over an order of magnitude estimated from the HRXRD results. Cross-sectional transmission electron microscopy observations clearly show that the formation and lateral propagation of macro-steps on the GaN surface play an important role in this dislocation reduction. A method for the reduction of threading dislocation density in GaN epilayers is proposed.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)

Optical trapping of colloidal particles and measurement of the defect line tension and colloidal forces in a thermotropic nematic liquid crystal

I. I. Smalyukh, A. N. Kuzmin, A. V. Kachynski, P. N. Prasad, and O. D. Lavrentovich

Appl. Phys. Lett. 86, 021913 (2005); http://dx.doi.org/10.1063/1.1849839 (3 pages)

Online Publication Date: 5 January 2005

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We demonstrate optical trapping and manipulation of transparent microparticles suspended in a thermotropic nematic liquid crystal with low birefringence. We employ the particle manipulation to measure line tension of a topologically stable disclination line and to determine colloidal interaction of particles with perpendicular surface anchoring of the director. The three-dimensional director fields and positions of the particles manipulated by laser tweezers are visualized by fluorescence confocal polarizing microscopy.
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61.30.Jf Defects in liquid crystals
78.20.Fm Birefringence
42.70.Df Liquid crystals
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
78.55.Bq Liquids
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
82.70.Dd Colloids

Limiting factors of room-temperature nonradiative photoluminescence lifetime in polar and nonpolar GaN studied by time-resolved photoluminescence and slow positron annihilation techniques

S. F. Chichibu, A. Uedono, T. Onuma, T. Sota, B. A. Haskell, S. P. DenBaars, J. S. Speck, and S. Nakamura

Appl. Phys. Lett. 86, 021914 (2005); http://dx.doi.org/10.1063/1.1851619 (3 pages) | Cited 29 times

Online Publication Date: 5 January 2005

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Room-temperature nonradiative lifetime (τnr) of the near-band-edge excitonic photoluminescence (PL) peak in {0001} polar, (11math0), (1math00), and (001) nonpolar GaN was shown to increase with the decrease in density or size of Ga vacancies (VGa) and with the decrease in gross density of point defects including complexes, leading to the increase in the PL intensity. As the edge threading dislocation density decreased, density or size of VGa tended to decrease and τnr tended to increase. However, there existed remarkable exceptions. The results indicate that nonradiative recombination process is governed not by single point defects, but by certain defects introduced with the incorporation of VGa, such as VGa-defect complexes.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.70.Bj Positron annihilation
61.72.J- Point defects and defect clusters
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
68.55.-a Thin film structure and morphology

Atomistic processes during nanoindentation of amorphous silicon carbide

Izabela Szlufarska, Rajiv K. Kalia, Aiichiro Nakano, and Priya Vashishta

Appl. Phys. Lett. 86, 021915 (2005); http://dx.doi.org/10.1063/1.1849843 (3 pages) | Cited 12 times

Online Publication Date: 5 January 2005

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Atomistic mechanisms of nanoindentation of a-SiC have been studied by molecular dynamics simulations. The load displacement curve exhibits a series of load drops, reflecting the short-range topological order similar to crystalline 3C–SiC. In contrast to 3C–SiC, the load drops are irregularly spaced and less pronounced. The damage is spatially more extended than in 3C–SiC, and it exhibits long-range oscillations consistent with the indenter size. Hardness is ∼ 60% lower than in 3C–SiC and is in agreement with experiment. The onset of plastic deformation occurs at depth ∼ 75% lower than in 3C–SiC.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
61.43.Bn Structural modeling: serial-addition models, computer simulation
68.35.Gy Mechanical properties; surface strains
81.40.Lm Deformation, plasticity, and creep
62.20.M- Structural failure of materials
62.20.F- Deformation and plasticity

Effects of two-dimensional electron gas on the optical properties of InAs/GaAs quantum dots in modulation-doped heterostructures

T. W. Kim, J. H. Kim, H. S. Lee, J. Y. Lee, and M. D. Kim

Appl. Phys. Lett. 86, 021916 (2005); http://dx.doi.org/10.1063/1.1849853 (3 pages) | Cited 2 times

Online Publication Date: 5 January 2005

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The Shubnikov–de Haas data showed that the carrier density of two-dimensional electron gas (2DEG) in the GaAs active region containing InAs quantum dot (QD) arrays embedded between modulation-doped Al0.25Ga0.75As/GaAs heterostructures increased with increasing doping concentration in the modulation layer. The transmission electron microscopy images showed that the sizes of the self-assembled InAs vertically stacked QD arrays inserted in the GaAs did not change significantly with increasing carrier density of the 2DEG. The photoluminescence (PL) spectra showed that the peaks corresponding to the interband transitions from the ground electronic subband to the ground heavy-hole subband of the InAs QDs shifted to the higher energy side with increasing density of the 2DEG and that the full width at half maximum of the PL spectrum increased slightly with increasing density of the 2DEG.
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73.63.Kv Quantum dots
78.67.Hc Quantum dots
73.21.La Quantum dots
78.55.Cr III-V semiconductors
61.72.S- Impurities in crystals
61.72.uj III-V and II-VI semiconductors
68.37.Lp Transmission electron microscopy (TEM)

Orientation-dependent x-ray absorption fine structure of ZnO nanorods

S.-W. Han, H.-J. Yoo, Sung Jin An, Jinkyoung Yoo, and Gyu-Chul Yi

Appl. Phys. Lett. 86, 021917 (2005); http://dx.doi.org/10.1063/1.1851616 (3 pages) | Cited 13 times

Online Publication Date: 6 January 2005

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The local structure of two samples of vertically well-aligned ZnO nanorods with average diameters of 13 and 37 nm were studied using orientation-dependent x-ray absorption fine structure (XAFS) at the Zn K edge. The aligned ZnO nanorod samples were fabricated on sapphire (0001) substrates with a catalyst-free metalorganic vapor-phase epitaxy method. The XAFS measurements showed that both nanorod samples have a well-ordered wurtzite structure and that no vacancy was observed at either site of zinc or oxygen atoms. However, we found that in both samples the lattice constants of a and b were shrunken by ∼ 0.04 Å while c was elongated by ∼ 0.1 Å, compared with those of their bulk counterparts. Furthermore, there was a substantial amount of disorder in the bond length of the only Zn–O pairs located near the ab plane. This may suggest that the terminating atoms at the boundaries of the nanorods are oxygen atoms.
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61.46.-w Structure of nanoscale materials
78.70.Dm X-ray absorption spectra

Nanoindentation and photoreflectance study on polycrystalline ternary Al–C–N thin films

A. L. Ji, L. B. Ma, C. Liu, P. Zheng, C. R. Li, and Z. X. Cao

Appl. Phys. Lett. 86, 021918 (2005); http://dx.doi.org/10.1063/1.1853507 (3 pages)

Online Publication Date: 6 January 2005

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Berkovich hardness and optical gap were determined by nanoindentation and photoreflectance measurement for ternary Al–C–N thin films of various compositions along with structural characterization. The deposits were fabricated by reactive magnetron sputtering of aluminum target onto Si(100) substrates, with the mixture of argon, nitrogen, and methane as precursor. High-resolution transmission electron microscopy and selected-area electron diffraction revealed a polycrystalline structure with rich defects in the film, and x-ray diffraction displays only one reflection at 2θ ≈ 36° from the basal planes. The hardness is over 26 GPa for all the deposits, it measures 53.4 GPa in the sample Al47C20N33. The optical gap, defined as the photon energy where (1/R)(dR/dE) maximizes, R is the photoreflectance, lies within 5.2 to 5.6 eV. These results indicate the wide-gap nature of aluminum carbonitrides, implying diverse potential applications of their thin films as protective coating of an ultraviolet detector, dielectric barrier layer in electronics, etc.
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68.60.Bs Mechanical and acoustical properties
78.66.Li Other semiconductors

Template-induced crystallization of amorphous SiO2 and its effects on the mechanical properties of TiN/SiO2 nanomultilayers

Lun Wei, Fanghua Mei, Nan Shao, Ming Kong, Geyang Li, and Jianguo Li

Appl. Phys. Lett. 86, 021919 (2005); http://dx.doi.org/10.1063/1.1853512 (3 pages) | Cited 15 times

Online Publication Date: 6 January 2005

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TiN/SiO2 nanomultilayers with various thicknesses of the SiO2 layer have been prepared by multi-target magnetron sputtering. Studies show that amorphous SiO2, which is more favorable under sputtering condition, crystallizes at smaller layer thickness (0.45–0.9 nm) due to the template effect of TiN layers. Correspondingly, multilayers exhibit coherent epitaxial growth with intensive (111) texture, and show significant hardness enhancement with maximum hardness of 44.5 GPa. Further increase in the SiO2 layer thickness (≳1 nm) leads to the formation of amorphous SiO2 which blocks the coherent growth of the films, and thus decreases the multilayer hardness gradually.
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68.65.Ac Multilayers

Interfacial reactions during GaN and AiN epitaxy on 4H– and 6H–SiC(0001)

Maria Losurdo, Pio Capezzuto, Giovanni Bruno, April Brown, Tong-Ho Kim, Changhyun Yi, D. N. Zakharov, and Z. Liliental-Weber

Appl. Phys. Lett. 86, 021920 (2005); http://dx.doi.org/10.1063/1.1852703 (3 pages) | Cited 5 times

Online Publication Date: 6 January 2005

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Thin layers of AlN and GaN have been grown by plasma-assisted molecular beam epitaxy on Si-face 4H– and 6H–SiC(0001)Si substrates. The impact of the SiC surface preparation and oxide removal via a Ga deposition and desorption process on the chemistry and structure of the GaN/SiC and AlN/SiC interfaces, and on the GaN/SiC subsurface reactivity is characterized. We also investigate the impact of this process on growth mode evolution.
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68.35.Fx Diffusion; interface formation
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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