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24 Feb 1997

Volume 70, Issue 8, pp. 919-1058

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A substrate-mode holographic collimating and beam shaping element for laser diodes

Jen-Tsorng Chang, Der-Chin Su, Zhi-Xian Huang, and Yang-Tung Huang

Appl. Phys. Lett. 70, 919 (1997); http://dx.doi.org/10.1063/1.118441 (3 pages) | Cited 3 times

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A new type of substrate-mode holographic collimating and beam shaping element for laser diodes is presented. Techniques and design considerations are described. A sample is fabricated and its function is demonstrated. It has many merits, such as easy fabrication, low cost, compactness of monolithic structure, and is easily used. © 1997 American Institute of Physics.
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42.40.Eq Holographic optical elements; holographic gratings
42.40.Pa Volume holograms
42.79.Ag Apertures, collimators
42.55.Px Semiconductor lasers; laser diodes

Nonlinear scanning laser microscopy by third harmonic generation

Y. Barad, H. Eisenberg, M. Horowitz, and Y. Silberberg

Appl. Phys. Lett. 70, 922 (1997); http://dx.doi.org/10.1063/1.118442 (3 pages) | Cited 168 times

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Third harmonic generation near the focal point of a tightly focused beam is used to probe microscopical structures of transparent samples. It is shown that this method can resolve interfaces and inhomogeneities with axial resolution comparable to the confocal length of the beam. Using 120 fs pulses at 1.5 μm, we were able to resolve interfaces with a resolution of 1.2 μm. Two-dimensional cross-sectional images have also been produced. © 1997 American Institute of Physics.
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07.60.Pb Conventional optical microscopes
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
68.35.Ct Interface structure and roughness

Third-order nonlinear optical properties of chalcogenide glasses

Hirohisa Kanbara, Seiji Fujiwara, Koichiro Tanaka, Hiroyuki Nasu, and Kazuyuki Hirao

Appl. Phys. Lett. 70, 925 (1997); http://dx.doi.org/10.1063/1.118443 (3 pages) | Cited 22 times

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Third-order nonlinear optical properties of chalocogenide glasses were investigated through third-harmonic generation (THG), optical Kerr shutter (OKS), and degenerate four-wave mixing (DFWM) measurements. We examined the dependence of the THG susceptibility on the absorption edge, thereby showing that the susceptibility rapidly increased as the absorption edge red shifted. Moreover, the THG susceptibility was compared with the OKS susceptibility. It was found that both susceptibilities almost coincided within the range of experimental errors. The OKS and DFWM experiments indicated that a high-speed compact optical switching device was obtained using the chalcogenide glasses. © 1997 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
42.70.Ce Glasses, quartz
78.20.Fm Birefringence

Spectral broadening measurements in poly(phenylene vinylene) polymer channel waveguides

Th. Gabler, R. Waldhäusl, A. Bräuer, F. Michelotti, H.-H. Hörhold, and U. Bartuch

Appl. Phys. Lett. 70, 928 (1997); http://dx.doi.org/10.1063/1.118462 (3 pages) | Cited 11 times

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In a polyconjugated main chain polymer strip waveguide the nonlinear, nonresonant refractive index n2 was measured by monitoring the signal spectrum broadening due to self-phase modulation. The two photon absorption coefficient α2 was obtained by calibrating the inverse transmission measurement. The nonlinear coefficients were determined to be n2 = 0.85×10−14 cm−2/W andα2 = 0.08 cm/GW at a wavelength λ=885.6 nm. The used polymer was poly[1,4-phenylene1,2-di(phenoxyphenyl)vinylene]. The result is in good agreement with interferometer measurements. The material is suitable for all-optical switching. © 1997 American Institute of Physics.
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42.65.Wi Nonlinear waveguides
42.65.An Optical susceptibility, hyperpolarizability
42.70.Jk Polymers and organics

Mid-infrared In1−xAlxSb/InSb heterostructure diode lasers

T. Ashley, C. T. Elliott, R. Jefferies, A. D. Johnson, G. J. Pryce, A. M. White, and M. Carroll

Appl. Phys. Lett. 70, 931 (1997); http://dx.doi.org/10.1063/1.118444 (3 pages) | Cited 19 times

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Stimulated emission at 5.1 μm was demonstrated from a broad area In1−xAlxSb/InSb heterostructure diode laser grown by molecular beam epitaxy. For a 5 μs pulse and a 500 Hz repetition rate the threshold current density was 1480 A cm−2 at 77 K and the maximum operating temperature was 90 K at a current density of 2680 A cm−2. Maximum peak power output was estimated to be 28 mW per facet at 77 K and 4500 A cm−2.
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42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission

Planar light-emitting devices fabricated with luminescent electrochemical polyblends

G. Yu, Q. Pei, and A. J. Heeger

Appl. Phys. Lett. 70, 934 (1997); http://dx.doi.org/10.1063/1.118445 (3 pages) | Cited 22 times

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Light emitting devices were fabricated in planar (surface cell) configurations with low operating voltage. Polymer blends composed of a red or green color luminescent polymer and solid state electrolyte were used as the active materials. Under external bias, electrochemical doping occurs in the vicinity of the contact, and a dynamic p-n junction forms between the electrodes. Light emission is observed in the junction area at bias voltages greater than 2 V, reaching 102cd/m2 at voltage well below 5 V. The planar configuration allows display devices to be hybridized with integrated circuits on a silicon wafer. On transparent substrates, such as glass or plastic films, light emission can be viewed from both sides of the device. Emissive displays in the planar surface cell configuration can be fabricated using roll-to-roll processing at room temperature without need for vacuum equipment. © 1997 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds

Modified substrate spontaneous emission in broad area semiconductor lasers

Malcolm W. Wright, Gregory C. Dente, David J. Bossert, and Michael L. Tilton

Appl. Phys. Lett. 70, 937 (1997); http://dx.doi.org/10.1063/1.118446 (3 pages) | Cited 3 times

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We observe modification of the spontaneous emission spectrum emitted through the substrate of a quantum well semiconductor laser. The effect is driven by the proximity of the quantum well active region to the p-side electrical contact of the device, representing an excellent example of cavity quantum electrodynamics. Modification of the spontaneous emission rate and spectrum can be substantial; it must be accounted for in order to infer modal gain or carrier heating phenomena in the device correctly. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors
42.50.-p Quantum optics

Time-resolved observation of thermal oscillations by transmission electron microscopy

N. Osakabe, K. Harada, M. I. Lutwyche, H. Kasai, and A. Tonomura

Appl. Phys. Lett. 70, 940 (1997); http://dx.doi.org/10.1063/1.118447 (3 pages) | Cited 9 times

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Time-dependent acoustic oscillations driven by stochastic thermal force have been observed by means of transmission electron microscopy. An electron-beam current passing in the vicinity of the edge of the vibrating sample, and thereby modulated, was led through an aperture at the image plane and measured with the electron counting technique as the power spectral density function, allowing the resonant frequency and the Q factor to be found. This enables estimation of the Young’s modulus and the internal friction. The method can be extended to the investigation of the elastic properties of nanoscaled samples. © 1997 American Institute of Physics.
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68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
62.30.+d Mechanical and elastic waves; vibrations
81.07.-b Nanoscale materials and structures: fabrication and characterization

The origin of nonlinearity in KTiOPO4

Dongfeng Xue and Siyuan Zhang

Appl. Phys. Lett. 70, 943 (1997); http://dx.doi.org/10.1063/1.118448 (3 pages) | Cited 17 times

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The origin of nonlinearity in KTiOPO4 was investigated quantitatively from the chemical bond viewpoint. All constituent chemical bonds in this crystal were considered and their contributions to the total linearity and nonlinearity were quantitatively determined. Calculated results agree satisfactorily with experimental data in both signs and numerical values. These results show us that TiO6 groups and P(1)O4 groups have relatively larger linear contributions and the nonlinearity derives from KOx (x = 8,9) groups and P(2)O4 groups. © 1997 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
42.70.Mp Nonlinear optical crystals
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Threshold sheath potential for the nucleation and growth of cubic boron nitride by inductively coupled plasma enhanced chemical-vapor deposition

Satoshi Amagi, Daisuke Takahashi, and Toyonobu Yoshida

Appl. Phys. Lett. 70, 946 (1997); http://dx.doi.org/10.1063/1.118449 (3 pages) | Cited 5 times

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The nucleation and growth conditions of c-BN films were studied in low-pressure inductively coupled plasma enhanced chemical-vapor deposition. The threshold sheath potentials needed for the nucleation and the growth of c-BN were sustained by two step Vsheath deposition. The threshold sheath potential for the growth Vsheathg was found to be significantly lower than the threshold value required for nucleation Vsheathn. Under our experimental condition, the values of Vsheathg and Vsheathn were found to be 45 and 65 V. © 1997 American Institute of Physics.
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68.55.Nq Composition and phase identification
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

AlxGa1−xN (0⩽x ⩽ 1) ultraviolet photodetectors grown on sapphire by metal-organic chemical-vapor deposition

D. Walker, X. Zhang, A. Saxler, P. Kung, J. Xu, and M. Razeghi

Appl. Phys. Lett. 70, 949 (1997); http://dx.doi.org/10.1063/1.118450 (3 pages) | Cited 54 times

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AlxGa1−xN (0⩽x⩽1) ultraviolet photoconductors with cutoff wavelengths from 365 to 200 nm have been fabricated and characterized. The maximum detectivity reached 5.5×108 cmHz1/2/W at a modulating frequency of 14 Hz. The effective majority carrier lifetime in AlxGa1−xN materials, derived from frequency-dependent photoconductivity measurements, has been estimated to be from 6 to 35 ms. The frequency-dependent noise spectrum shows that it is dominated by Johnson noise at high frequencies for low-Al-composition samples. © 1997 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
72.40.+w Photoconduction and photovoltaic effects
72.80.Ey III-V and II-VI semiconductors

Misfit grainlets: Point strain sources compensating misfit during epitaxial growth

M. Albrecht, S. Christiansen, and H. P. Strunk

Appl. Phys. Lett. 70, 952 (1997); http://dx.doi.org/10.1063/1.118451 (3 pages) | Cited 3 times

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We propose a misfit relaxation mechanism that may occur during growth in highly misfitting layers. It is based on a misfit compensating distribution of physical point strain sources at the interface between layer and substrate instead of misfit dislocations. These point strain sources are realized by interfacial islands (misfit grainlets) that have a lattice misfit opposite in sign to that of the surrounding epitaxial layer, in most cases brought about by an orientation relationship different from that of the surrounding layer to the substrate. We demonstrate the effectiveness in strain relaxation of misfit grainlets with an analysis of the interface structure of GaN on sapphire and discuss the formation of misfit grainlets in terms of a self-organized island growth process. © 1997 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
61.72.Lk Linear defects: dislocations, disclinations

Lateral and vertical ordering in multilayered self-organized InGaAs quantum dots studied by high resolution x-ray diffraction

A. A. Darhuber, V. Holy, J. Stangl, G. Bauer, A. Krost, F. Heinrichsdorff, M. Grundmann, D. Bimberg, V. M. Ustinov, P. S. Kop’ev, A. O. Kosogov, and P. Werner

Appl. Phys. Lett. 70, 955 (1997); http://dx.doi.org/10.1063/1.118463 (3 pages) | Cited 42 times

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We have studied multiple layers of self-organized InGaAs-islands grown on GaAs by x-ray diffraction reciprocal space mapping. We found an anisotropy of the dot spacing in [100] and [110] direction consistent with an ordering of the dots in a two-dimensional square lattice with main axes along the [100] direction and a lattice parameter of 55 nm. The nearly perfect vertical alignment (stacking) of the dots was deduced from the diffraction peak shape. © 1997 American Institute of Physics.
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61.05.C- X-ray diffraction and scattering
68.55.-a Thin film structure and morphology
68.35.Ct Interface structure and roughness
81.05.Dz II-VI semiconductors

Raman spectroscopy investigation of size effects in cubic boron nitride

T. Werninghaus, J. Hahn, F. Richter, and D. R. T. Zahn

Appl. Phys. Lett. 70, 958 (1997); http://dx.doi.org/10.1063/1.118452 (3 pages) | Cited 49 times

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Raman spectra were taken of cubic boron nitride (c-BN) crystals with diameters between 100 nm and 1 mm. The Raman line shape of the optical phonons was found to become increasingly asymmetric towards lower frequency shifts, broader and weaker with decreasing crystal diameters. The results can be explained in terms of a spatial correlation model. The corresponding correlation lengths lie in the nanometer range, i.e. several orders of magnitude below the actual crystallite sizes as determined by electron microscopy, thus revealing a high defect density. An additional examined typical c-BN film on a Si(100) substrate exhibits even weaker and broader structures consistent with an even higher defect density. © 1997 American Institute of Physics.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.30.Fs III-V and II-VI semiconductors
68.55.-a Thin film structure and morphology

Determining the distribution of silicon monofluoride on hydrofluoric acid-treated Si (111) surface by exchange reaction with molecules at the solid/liquid interface

Munehisa Mitsuya

Appl. Phys. Lett. 70, 961 (1997); http://dx.doi.org/10.1063/1.118311 (3 pages) | Cited 1 time

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Silicon monofluoride (Si–F) species on hydrofluoric acid (HF)-treated silicon surface have been shown to be quantitatively replaced by nucleophilic reagents at the solid/liquid interface, but some Si–F remain intact. The chemisorption of molecules with larger dimensions results in a decrease in the proportion of fluorine that is replaced. These results can be attributed to steric hindrance by the adsorbed molecules. This is explained by a model in which Si–F are grouped together to form islands of Si–F species on a predominantly H-terminated Si surface. © 1997 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Time-resolved high-resolution electron microscopy of solid state direct bonding of gold and zinc oxide nanocrystallites at ambient temperature

Tokushi Kizuka, Kanji Yamada, and Nobuo Tanaka

Appl. Phys. Lett. 70, 964 (1997); http://dx.doi.org/10.1063/1.118312 (3 pages) | Cited 5 times

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Approach, contact, and bonding processes between different kinds of materials, gold (Au) and zinc oxide (ZnO) nanocrystallites were observed at atomic scale and at time resolution of 1/60 s. The nanocrystallites contact spontaneously when they approach at a few atomic distances under an intense electron irradiation. It was found that a Au/ZnO interface forms at ambient temperature without any sintering aid after the contact. © 1997 American Institute of Physics.
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68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
61.46.-w Structure of nanoscale materials
68.35.Fx Diffusion; interface formation

Temperature determination in shocked condensed materials using Raman scattering

G. I. Pangilinan and Y. M. Gupta

Appl. Phys. Lett. 70, 967 (1997); http://dx.doi.org/10.1063/1.118477 (3 pages) | Cited 11 times

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The use of time-resolved Raman scattering measurements to determine temperature in shocked materials is demonstrated. Experimental data were obtained by monitoring the stokes and antistokes intensities of the 460 cm−1 vibrational mode, at 50 ns intervals, in liquid carbon tetrachloride shocked to 12 GPa using step wise loading. The ratio of antistokes to stokes intensities changes in a pronounced manner with increasing pressure. Procedures to obtain precise temperatures are outlined, and improvements for future work are indicated. © 1997 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
78.30.C- Liquids
07.20.Ka High-temperature instrumentation; pyrometers
05.70.-a Thermodynamics

Lateral stiffness of the tip and tip-sample contact in frictional force microscopy

M. A. Lantz, S. J. O’Shea, A. C. F. Hoole, and M. E. Welland

Appl. Phys. Lett. 70, 970 (1997); http://dx.doi.org/10.1063/1.118476 (3 pages) | Cited 60 times

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In atomic force and frictional force microscopy, quantitative interpretation of lateral stiffness at the tip-sample contact requires a detailed understanding of all factors contributing to the frictional force as measured in a typical experiment. We used a scanning transmission electron microscope to image and determine the geometry of the tip apex of a variety of atomic force microscope cantilevers. On the basis of this measured structure, we then used finite element analysis to model the lateral stiffness of the tip and found that the tip stiffness is often smaller than the lateral stiffness of the cantilever. Furthermore, we analyzed the stiffness of the tip sample contact and found that for sharp tips the contact stiffness can also be comparable to the lateral stiffness of the cantilever. If these two effects are ignored, significant errors can result in the calculation of lateral forces. We demonstrated the effects of lateral tip and contact stiffness experimentally and used the measurements to calculate the radius of the tip-sample contact. © 1997 American Institute of Physics.
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07.79.Sp Friction force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Novel post-etching treatment of small windows in oxide for selective epitaxial growth

J. W. H. Maes, J. Caro, C. C. G. Visser, T. Zijlstra, E. W. J. M. van der Drift, S. Radelaar, F. D. Tichelaar, and E. J. M. Fakkeldij

Appl. Phys. Lett. 70, 973 (1997); http://dx.doi.org/10.1063/1.118471 (3 pages)

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A novel post-etching treatment of small windows in oxide for selective epitaxial Si growth is presented. The treatment is a short reactive ion etch in a Cl2 plasma, applied after window etching. Transmission electron microscopy (TEM) analysis of grown structures shows that high quality epitaxy is obtained in windows as small as 46 nm, indicating effective removal of fluorocarbon contamination. X-ray photoemission spectroscopy (XPS) analysis of the Si surface confirms this. From electrical measurements on small Si point contacts fabricated with this treatment, we deduce that the constriction is high quality single-crystalline Si, in agreement with the TEM and XPS results.   © 1997 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Electronic properties of osmium disilicide

A. B. Filonov, D. B. Migas, V. L. Shaposhnikov, N. N. Dorozhkin, V. E. Borisenko, and H. Lange

Appl. Phys. Lett. 70, 976 (1997); http://dx.doi.org/10.1063/1.118453 (2 pages) | Cited 7 times

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Electronic property calculation of OsSi2 performed by the linear muffin-tin orbital method within the local density approximation scheme has shown the material to be an indirect gap semiconductor with a gap value of 0.95 eV. A direct transition with appreciable oscillator strength at 1.14 eV is predicted. © 1997 American Institute of Physics.
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71.20.Nr Semiconductor compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Cubo-octahedral B12 clusters in silicon crystal

Masakuni Okamoto, Kazunobu Hashimoto, and Kunio Takayanagi

Appl. Phys. Lett. 70, 978 (1997); http://dx.doi.org/10.1063/1.118454 (3 pages) | Cited 12 times

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We have calculated a new stable structure and the electronic structure of boron clusters in silicon crystal. According to our calculation, which was based on the first-principles local density functional approach for Si54B12H60 clusters, the cubo-octahedral B12 cluster was found to be more stable than the icosahedral one proposed previously. The total energy difference was about 4.6 eV. The analysis of the partial density of states showed that the cubo-octahedral B12 cluster should act as a double acceptor. © 1997 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
61.66.Bi Elemental solids
73.22.-f Electronic structure of nanoscale materials and related systems

Role of self-formed InGaN quantum dots for exciton localization in the purple laser diode emitting at 420 nm

Yukio Narukawa, Yoichi Kawakami, Mitsuru Funato, Shizuo Fujita, Shigeo Fujita, and Shuji Nakamura

Appl. Phys. Lett. 70, 981 (1997); http://dx.doi.org/10.1063/1.118455 (3 pages) | Cited 473 times

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Structural analysis was performed on a purple laser diode composed of In0.20Ga0.80N (3 nm)/ In0.05Ga0.95N (6 nm) multiple quantum wells, by employing transmission electron microscopy and energy-dispersive x-ray microanalysis, both of which are assessed from the cross-sectional direction. It was found that the contrast of light and shade in the well layers corresponds to the difference in In composition. The main radiative recombination was attributed to excitons localized at deep traps which probably originate from the In-rich region in the wells acting as quantum dots. Photopumped lasing was observed at the high energy side of the main spontaneous emission bands. © 1997 American Institute of Physics.
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71.35.-y Excitons and related phenomena
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
78.66.Fd III-V semiconductors
78.45.+h Stimulated emission

Surface emission of InxGa1−xN epilayers under strong optical excitation

H. X. Jiang, J. Y. Lin, M. Asif Khan, Q. Chen, and J. W. Yang

Appl. Phys. Lett. 70, 984 (1997); http://dx.doi.org/10.1063/1.118456 (3 pages) | Cited 3 times

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Effects of strong optical excitation on the properties of surface emission from an InGaN/GaN heterostructure grown by metal-organic chemical-vapor deposition have been investigated. An intriguing feature observed was that as the excitation intensity increased the surface emission spectrum evolved abruptly from a single dominating band to two dominating bands at a critical intensity. This phenomenon has a sharp phase transition or a switching character and can be accounted for by (i) the formation of an electron–hole plasma state in the InGaN vertical cavity under strong optical excitation, (ii) the photoreflectance effect (variation of index of refraction with excitation intensity), and (c) the Fabry–Pérot interference effect in the InGaN vertical cavity. These findings are expected to have impact on the design of the laser structures, in particular on the design of the vertical-cavity surface-emitting laser diodes based on III-nitride wide-band-gap semiconductors. © 1997 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
42.70.Hj Laser materials

Optical gain for wurtzite GaN with anisotropic strain in c plane

K. Domen, K. Horino, A. Kuramata, and T. Tanahashi

Appl. Phys. Lett. 70, 987 (1997); http://dx.doi.org/10.1063/1.118457 (3 pages) | Cited 39 times

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We calculated band structures of (1100)-oriented GaN with various strains. We found that introducing anisotropic strain in the c plane separates heavy- and light-hole bands. We also found that a tensile strain in the (1100) plane makes the light-hole band topmost. These two effects result in a reduction in the density of states at the valence-band edge. In this way we can significantly reduce the transparent carrier density to generate gain. © 1997 American Institute of Physics.
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78.45.+h Stimulated emission
85.60.Jb Light-emitting devices

Epitaxy of Al films on GaN studied by reflection high-energy electron diffraction and atomic force microscopy

Q. Z. Liu, L. Shen, K. V. Smith, C. W. Tu, E. T. Yu, S. S. Lau, N. R. Perkins, and T. F. Kuech

Appl. Phys. Lett. 70, 990 (1997); http://dx.doi.org/10.1063/1.118458 (3 pages) | Cited 5 times

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Epitaxy of Al films deposited on GaN has been studied using reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), x-ray diffraction, and ion channeling techniques. Al (111) films have been found to grow epitaxially on GaN (0001) surfaces with Al 〈211〉‖GaN〈2110〉. For growth at 15 and 150 °C with a deposition rate of 0.26 Å/s, the epitaxial quality of the film was poor initially, as evidenced by the observation of diffuse RHEED patterns. After a few monolayers, a sharp and streaky RHEED pattern develops and is maintained during subsequent deposition, indicating an improvement in epitaxial quality with a two-dimensional growth mode. AFM studies indicate that the initial GaN surface quality is a significant factor in achieving epitaxial growth, and that the size of Al epitaxial islands increases substantially for higher growth temperatures. X-ray diffraction and ion channeling results confirm the epitaxial nature of the Al films in spite of a significant lattice mismatch of 10.2%. © 1997 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
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