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28 Oct 1996

Volume 69, Issue 18, pp. 2623-2782

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Differential microscopy by conventional electron off‐axis holography

Takayoshi Tanji, Qingxin Ru, and Akira Tonomura

Appl. Phys. Lett. 69, 2623 (1996); http://dx.doi.org/10.1063/1.117555 (3 pages) | Cited 2 times

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Differential microscopy is realized by conventional off‐axis electron holography with an electron biprism behind the specimen. Two phase images reconstructed from two holograms which are obtained with slightly different potentials of the electron biprism are utilized to make a one‐dimensional differential image. Polystyrene latex particles which are charged by electron irradiation are used to demonstrate that the differential image is independent of the distortion of a reference wave. © 1996 American Institute of Physics.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
61.05.jp Electron holography
41.75.Fr Electron and positron beams

Active mode locking at 50 GHz repetition frequency by half‐frequency modulation of monolithic semiconductor lasers integrated with electroabsorption modulators

Kenji Sato, Isamu Kotaka, Yasuhiro Kondo, and Mitsuo Yamamoto

Appl. Phys. Lett. 69, 2626 (1996); http://dx.doi.org/10.1063/1.117556 (3 pages) | Cited 25 times

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Active mode locking achieved at a 50 GHz repetition frequency by modulation at half (25 GHz) the cavity resonance frequency using a monolithic mode‐locked InGaAsP laser integrated with an electroabsorption modulator is described. A pulse width of around 3 ps and a high suppression ratio of more than 33 dB of the intensity modulation at the driving frequency are obtained. © 1996 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Px Semiconductor lasers; laser diodes

Bulk periodically poled MgO‐LiNbO3 by corona discharge method

Akinori Harada and Yasukazu Nihei

Appl. Phys. Lett. 69, 2629 (1996); http://dx.doi.org/10.1063/1.117540 (3 pages) | Cited 25 times

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We propose and demonstrate a novel corona discharge method for the fabrication of bulk periodically poled MgO‐LiNbO3 substrates. The bulk periodic domain inversion has been successfully formed with a first‐order modulation period of 5.2 μm for a wavelength of 980 nm over a 6.5 mm interaction length in a Z‐cut 0.4‐mm‐thick MgO‐LiNbO3 substrate for the first time. It was found that MgO‐LiNbO3 crystal is capable of forming domain inversion under a low applied voltage of no more than 6 kV/mm, which is lower than the case of LiNbO3 and LiTaO3. A 490 nm blue light power of 6.7 mW was achieved in a single pass through periodically poled MgO‐LiNbO3, by using a high‐power monolithically integrated flared master oscillator power amplifier of 790 mW as a fundamental source. © 1996 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Optical lock‐in vibration detection using photorefractive frequency domain processing

Thomas Chatters Hale and Ken Telschow

Appl. Phys. Lett. 69, 2632 (1996); http://dx.doi.org/10.1063/1.117541 (3 pages) | Cited 3 times

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An optical method for vibration detection and spectral analysis based on photorefractive frequency domain processing is presented. The method utilizes the photorefractive effect in selected materials (bismuth silicon oxide) for synchronous detection of the optical phase shift of an object beam scattered from a vibrating specimen surface. Four‐wave mixing and lock‐in detection allow measurement of both the vibration amplitude and phase. Narrow‐bandwidth detection can be achieved at frequencies from the photorefractive response limit to the reciprocal of the photoinduced carrier recombination time. © 1996 American Institute of Physics.
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42.87.-d Optical testing techniques
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
81.70.Fy Nondestructive testing: optical methods

Reverse bias voltage dependent pulse shape and transmission change through a semiconductor saturable absorber

Dug K. Kim

Appl. Phys. Lett. 69, 2635 (1996); http://dx.doi.org/10.1063/1.117542 (3 pages)

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The effect of reverse bias voltage on optical transmission through a waveguide semiconductor saturable absorber is measured for various optical input pulse energies. Reverse bias voltage dependent pulse shape narrowing after a single pass through the device is also observed. Experimental results show that the transmission through the device can be controlled very effectively by modulating the reverse bias voltage on the device when the input pulse energy is low so that the absorption of the saturable absorber is unsaturated. We believe that this kind of controllable semiconductor saturable absorber can be used for many laser systems or modulator and limiter applications in optical communication systems. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Photonic band‐structure effects in the visible and near ultraviolet observed in solid‐state dielectric arrays

A. Rosenberg, R. J. Tonucci, and E. A. Bolden

Appl. Phys. Lett. 69, 2638 (1996); http://dx.doi.org/10.1063/1.117543 (3 pages) | Cited 16 times

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Two‐dimensional photonic band‐structure effects have been observed in the visible and near‐uv regions, between 350 and 800 nm. These effects appear in all‐solid‐state arrays of glass cylinders in a glass matrix. The arrays have center‐to‐center nearest‐neighbor separations between 0.188 and 0.278 μm, perfect long‐range order, and low refractive index contrast. For light propagating perpendicular to the cylinder axes, very narrow attenuations appear in the transmission spectra as a result of the photonic band structure. The positions of these attenuations are determined by the periodicity, composition, and symmetry of the arrays. © 1996 American Institute of Physics.
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42.70.Qs Photonic bandgap materials

Ultrasonic wave propagation in reticulated foams saturated by different gases: High frequency limit of the classical models

Ph. Leclaire, L. Kelders, W. Lauriks, J. F. Allard, and C. Glorieux

Appl. Phys. Lett. 69, 2641 (1996); http://dx.doi.org/10.1063/1.117544 (3 pages) | Cited 15 times

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Transmission experiments are performed on high porosity reticulated polyurethane foams saturated by different gases at ultrasonic frequencies up to 800 kHz. An excess attenuation is observed at high frequencies, when the wavelength is not sufficiently large compared to the lateral dimensions of the fibers. At lower frequencies, these experiments lead by using classical models of equivalent fluids, to a fast and reliable method for determining the characteristic length Λ. © 1996 American Institute of Physics.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
82.70.Rr Aerosols and foams

Diagnostics of a non‐equilibrium inductively coupled plasmas in argon

Akifumi Okigawa, Zoran Lj.Petrović, Masahiro Tadokoro, Toshiaki Makabe, Nobuhiko Nakano, and Akihiko Itoh

Appl. Phys. Lett. 69, 2644 (1996); http://dx.doi.org/10.1063/1.117545 (3 pages) | Cited 12 times

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An apparatus including a robot manipulated optical system has been built to provide absolute emission data from an inductively coupled plasma operating in argon in non‐equilibrium conditions. Data for the two‐dimensional population densities of one of the excited states of neutral argon ArI are presented together with the Langmuir probe data for electron density and plasma potential. Measurements were performed at 500 mTorr and 50 mTorr and with 100 sccm flow of argon under the constant power condition, 100 W. The data show that excitation profile is almost identical to the radial profile of electron density. At higher pressure maximum excitation and electron density are produced close to the walls, while at low pressure maximum excitation is at the center of the vessel and a high field is formed close to the walls. © 1996 American Institute of Physics.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Dg Plasma sources

Laterally structured ZnCdSe/ZnSe superlattices by diffusion induced disordering

M. Kuttler, M. Strassburg, V. Türck, R. Heitz, U. W. Pohl, D. Bimberg, E. Kurtz, G. Landwehr, and D. Hommel

Appl. Phys. Lett. 69, 2647 (1996); http://dx.doi.org/10.1063/1.117546 (3 pages) | Cited 9 times

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Thermally induced disordering of ZnCdSe/ZnSe superlattices was studied by secondary‐ion‐mass‐spectroscopy and cathodoluminescence. The structures were grown by molecular beam epitaxy and annealed in Zn, H2, or Se atmosphere. In Zn atmosphere the superlattice was found to be stable up to 500 °C, whereas a heat treatment in H2 and Se atmosphere leads to a complete intermixing at temperatures of 450 and 430 °C, respectively. A Si3N4 stripe was used to protect the superlattice locally from the annealing atmosphere and to achieve a laterally structured intermixing. The disordering area is controlled to better than 600 nm. © 1996 American Institute of Physics.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.60.Hk Cathodoluminescence, ionoluminescence

Direct imaging of impurity‐induced Raman scattering in GaN

F. A. Ponce, J. W. Steeds, C. D. Dyer, and G. D. Pitt

Appl. Phys. Lett. 69, 2650 (1996); http://dx.doi.org/10.1063/1.117547 (3 pages) | Cited 26 times

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The donor impurity distribution in a GaN epitaxial layer was studied using Raman imaging. The A1(LO) Raman line at 735 cm−1 is found to be inversely correlated to the presence of silicon in GaN due to phonon interaction with the free carrier plasma associated with donor impurities in the material. The spatial variation of the A1(LO) signal was imaged directly using newly developed instrumentation. Features with dimension of about 0.5 μm are observed in faceted GaN crystallites. This variation in free carrier concentration is attributed to preferential donor impurity incorporation during growth. © 1996 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Eq III-V semiconductors

Fabrication of high frequency nanometer scale mechanical resonators from bulk Si crystals

A. N. Cleland and M. L. Roukes

Appl. Phys. Lett. 69, 2653 (1996); http://dx.doi.org/10.1063/1.117548 (3 pages) | Cited 155 times

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We report on a method to fabricate nanometer scale mechanical structures from bulk, single‐crystal Si substrates. A technique developed previously required more complex fabrication methods and an undercut step using wet chemical processing. Our method does not require low pressure chemical vapor deposition of intermediate masking layers, and the final step in the processing uses a dry etch technique, avoiding the difficulties encountered from surface tension effects when wet processing mechanically delicate or large aspect ratio structures. Using this technique, we demonstrate fabrication of a mechanical resonator with a fundamental resonance frequency of 70.72 MHz and a quality factor of 2×104. © 1996 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
81.05.Cy Elemental semiconductors
62.30.+d Mechanical and elastic waves; vibrations
85.40.Hp Lithography, masks and pattern transfer

Structures and defects induced during annealing of sputtered near‐equiatomic NiTi shape memory thin films

F. F. Gong, H. M. Shen, and Y. N. Wang

Appl. Phys. Lett. 69, 2656 (1996); http://dx.doi.org/10.1063/1.117549 (3 pages) | Cited 3 times

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Structures and defects induced during annealing were studied in free‐standing NiTi thin films produced by rf magnetron sputtering. Ni4Ti3 precipitates coherent with the (B2) matrix do not affect the shape memory behavior of the thin films annealed at 550 °C for short times. With the further increase of the annealing time and/or temperature, less coherent Ni4Ti3 precipitates develop and hinder the shape memory behavior. The embrittlement of the annealed films probably results from grain–boundary precipitation, thermal etching, and stress gradients. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
07.10.Cm Micromechanical devices and systems

Highly insulative barium zirconate‐titanate thin films prepared by rf magnetron sputtering for dynamic random access memory applications

T. B. Wu, C. M. Wu, and M. L. Chen

Appl. Phys. Lett. 69, 2659 (1996); http://dx.doi.org/10.1063/1.117550 (3 pages) | Cited 31 times

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Polycrystalline thin films of Ba(ZrxTi1−x)O3 with x=0–0.4 and a thickness of ∼180 nm were deposited on platinum‐coated silicon substrates by rf magnetron sputtering at 500 °C. Ba‐rich targets were used to prepare films of stoichiometric composition. The film having x=0.12 exhibited a satisfactory dielectric property of dielectric constant, k≊300, and dissipation factor, tan δ<0.02, at frequencies from 103 to 106 Hz under ambient temperatures ranging from 20 to 180 °C. More importantly, the film showed a very stable and highly insulative characteristic against applied voltage. The leakage current density J increases only smoothly to a value less than 10−7 A/cm2 followed by an Ohmic relation of J=σE with σ=1.4×10−14 (Ω cm)−1 up to an extremely high electric field E of 5.6 MV/cm without any sign of abrupt increase of leakage current or electrical breakdown. Also, no time‐dependent electric degradation was observed for the film subjected to an electric field as high as 5 MV/cm at room temperature up to 3600 s of measurement. © 1996 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
73.61.Ng Insulators
81.15.Cd Deposition by sputtering

Electron field emission from diamond tips prepared by ion sputtering

Christoph Nützenadel, Olivier M. Küttel, Oliver Gröning, and Louis Schlapbach

Appl. Phys. Lett. 69, 2662 (1996); http://dx.doi.org/10.1063/1.117551 (3 pages) | Cited 15 times

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In this letter we report the field emission from cones etched into a synthetic‐type IIb (100) oriented boron‐doped diamond crystal. The cones were produced with an ion sputtering process. With a high‐resolution scanning electron microscope we found the curvature radius at the end of the cones to be less than 10 nm. The length of these cones is in the range of 10 μm giving a field enhancement of approx. 1000. Field emission started at field strength of 2 V/μm, and at 3.8 V/μm 10 nA were measured using a spherical anode of 4 mm diam. From a Fowler‐Nordheim fit the work function could be deduced to be 3–4 eV. Hence, electrons are emitted from the valence band. © 1996 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.05.ub Fullerenes and related materials
85.45.Fd Field emission displays (FEDs)

Anomalous temperature dependence of persistent photoconductivity in C60 single crystal

K. C. Chiu, J. S. Wang, Y. T. Dai, and Y. F. Chen

Appl. Phys. Lett. 69, 2665 (1996); http://dx.doi.org/10.1063/1.117552 (3 pages) | Cited 9 times

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The temperature dependence of persistent photoconductivity (PPC) has been investigated in high‐quality C60 single crystals. We found that the rotational order and disorder phase transition (Tc≊260 K) can significantly change the PPC behavior. At temperatures above Tc, the PPC relaxation rate increases as temperature increases. Quite surprisingly, in the region T<Tc, the PPC relaxation rate decreases with increasing temperature. Our result clearly indicates that the underlying mechanism of the PPC effect involves the motion of the C60 molecule. © 1996 American Institute of Physics.
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72.80.Rj Fullerenes and related materials
72.40.+w Photoconduction and photovoltaic effects

Correlation of the dispersed particles surface properties with the electrorheological response

Tian Hao and Yuanze Xu

Appl. Phys. Lett. 69, 2668 (1996); http://dx.doi.org/10.1063/1.117553 (3 pages) | Cited 2 times

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A set of oxidized polyacrylonitrile materials of different surface situations were employed to examine how the dispersed particles surface properties influence the electrorheological (ER) response. The shear stresses of these ER fluids were found to peak for the surface tension and the surface polarity of the dispersed particles, which could be qualitatively understood with our recent finding that the large dielectric loss, along with the large dielectric constant, are argued for good ER performance. Our findings have the direct implication that the ER effect would be most likely improved by means of certain surface modification methods, especially some chemical methods like the molecular design method, which perhaps can provide a good approach to develop the expected ER solid materials. Our results would also be significant for selecting ER solid materials and understanding the ER mechanism. A further theoretical work should be performed in the future. © 1996 American Institute of Physics.
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83.80.Gv Electro- and magnetorheological fluids
83.80.Hj Suspensions, dispersions, pastes, slurries, colloids
83.80.Iz Emulsions and foams
68.03.Cd Surface tension and related phenomena

Studies of film growth processes and surface structural characterization of ferroelectric memory‐compatible SrBi2Ta2O9 layered perovskites via in situ, real‐time ion‐beam analysis

O. Auciello, A. R. Krauss, J. Im, D. M. Gruen, E. A. Irene, R. P. H. Chang, and G. E. McGuire

Appl. Phys. Lett. 69, 2671 (1996); http://dx.doi.org/10.1063/1.117554 (3 pages) | Cited 7 times

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In situ, real‐time studies of layered perovskite SrBi2Ta2O9 (SBT) film growth processes were performed using a time‐of‐flight ion scattering and recoil spectroscopy (TOF ISARS) technique. These studies revealed two important features related to the synthesis of SBT films via ion‐beam sputter‐deposition, namely: (a) atomic oxygen originating from a multicomponent SBT target during the sputtering process is incorporated in the growing film more efficiently than molecular oxygen; and (b) the SBT surface appears to be terminated in an incomplete (Bi2O2)2+layer with a top surface of oxygen atoms, which may be responsible for the high resistance to polarization fatigue exhibited by Pt/SBT/Pt capacitors. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.05.Np Atom, molecule, and ion scattering (for structure determination only)
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Transition from self‐organized InSb quantum‐dots to quantum dashes

T. Utzmeier, P. A. Postigo, J. Tamayo, R. García, and F. Briones

Appl. Phys. Lett. 69, 2674 (1996); http://dx.doi.org/10.1063/1.117674 (3 pages) | Cited 20 times

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We have grown self‐organized InSb quantum dots on semi‐insulating InP (001) substrates by molecular beam epitaxy. We studied the size dependency of the uncapped InSb quantum dots on the nominal thickness of the deposited InSb by atomic force microscopy. The dot sizes have a pronounced minimum at about 2.2 monolayers of InSb. After a nominal thickness of 3.2 monolayers we observe a drastic change of the dot shape, from quantum dots to quantum dashes. From there on the dots grow in a quasicylindric shape aligned in the (110) direction. © 1996 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Kinetic roughening and smoothing of the crystalline–amorphous interface during solid phase epitaxial crystallization of GeSi alloy layers

R. G. Elliman and W. C. Wong

Appl. Phys. Lett. 69, 2677 (1996); http://dx.doi.org/10.1063/1.117675 (3 pages) | Cited 5 times

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The morphology of the crystalline–amorphous interface is studied during solid‐phase epitaxial crystallization of amorphous GeSi alloy layers with depth‐dependent Ge distributions. The interface is shown to undergo an initial strain‐induced roughening transition when the Ge concentration exceeds 6.6 at. %. As crystallization continues in strain‐relaxed material the interface is shown to further roughen or smooth in response to changes in the Ge distribution. This evolution of the interface morphology is shown to be a consequence of kinetic effects whereby the differential velocity between the leading and trailing edges of the rough interface increases in regions of increasing Ge concentration and decreases in regions of decreasing Ge concentration. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Np Solid phase epitaxy; growth from solid phases
68.35.Ct Interface structure and roughness

Iodine use in solid‐source III–V molecular‐beam epitaxy

M. Micovic, F. Flack, R. W. Streater, and A. J. SpringThorpe

Appl. Phys. Lett. 69, 2680 (1996); http://dx.doi.org/10.1063/1.117676 (3 pages) | Cited 6 times

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Use of iodine for in situ etching of GaAs, AlAs, and InAs in solid‐source molecular‐beam epitaxy has been explored. Reflectance high‐energy electron‐diffraction intensity oscillations have been observed during iodine etching of GaAs and InAs, indicating a molecular layer‐by‐layer nature of material removal. Etch rates of GaAs and InAs determined from the period of the oscillations are comparable for a given iodine flux. Secondary‐ion‐mass spectroscopy depth profiles indicate that the etching of AlAs is negligible, and that iodine can be used as a selective etch which stops on AlAs or AlGaAs layers. Electrical properties of GaAs layers grown with an iodine beam impinging on the surface are comparable to those of the layers grown without iodine. Use of iodine for the surface cleaning of GaAs has also been examined. Our results show that iodine etching prior to growth reduces the level of carbon contamination at the substrate epilayer interface. © 1996 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.40.Sz Deposition technology

Physical origins of temperature variation and background radiation associated with pyrometric interferometry measurement during III–V molecular‐beam‐epitaxy growth

J. J. Zhou, Y. Li, P. Thompson, D. L. Sato, H. P. Lee, and J. M. Kuo

Appl. Phys. Lett. 69, 2683 (1996); http://dx.doi.org/10.1063/1.117677 (3 pages)

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The physical origins of temperature variation and background radiation associated with in situ pyrometric interferometry (PI) monitoring during III–V molecular‐beam epitaxy are examined. By means of complementary PI and diffused reflectance spectroscopy measurements on GaAs and GaAs/AlAs structures grown at different temperature, the temperature variations due to the changes of sample emissivity and radiative heating from the Knudsen cells are identified and characterized. The studies will lead to more accurate modeling of PI signal and better control of substrate temperature. © 1996 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
07.20.Ka High-temperature instrumentation; pyrometers

Room temperature electroluminescence from dislocation‐rich silicon

Einar Ö. Sveinbjörnsson and Jörg Weber

Appl. Phys. Lett. 69, 2686 (1996); http://dx.doi.org/10.1063/1.117678 (3 pages) | Cited 36 times

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We report on electroluminescence at room temperature from forward biased n+–p silicon diodes containing high densities (108–109 cm−2) of dislocations at the junction interface. In addition to electroluminescence from band‐to‐band transitions, we observe a signal with a comparable intensity peaked at ∼1.6 μm (0.78 eV). From luminescence studies below room temperature we deduce that the 1.6 μm emission originates from the well known dislocation‐related center D1. The D1 electroluminescence intensity at room temperature increases linearly with current density with no observable saturation. The external efficiency of the D1 electroluminescence at room temperature was estimated to be of the order 10−6. © 1996 American Institute of Physics.
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78.60.Fi Electroluminescence
78.66.Db Elemental semiconductors and insulators
61.72.Lk Linear defects: dislocations, disclinations

Photon‐assisted tunneling in GaAs/AlGaAs superlattices up to room temperature

S. Zeuner, S. J. Allen, K. D. Maranowski, and A. C. Gossard

Appl. Phys. Lett. 69, 2689 (1996); http://dx.doi.org/10.1063/1.117679 (3 pages) | Cited 9 times

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Photon‐assisted transport is shown to be a remarkably robust phenomenon in sequential resonant superlattices with a large energy separation between the ground state and the first excited state of the quantum wells. Photon‐assisted tunneling involving up to seven photons per tunneling event, stands out very clearly. The one‐photon channel is observed up to 300 K. This implies that these superlattices are a gain medium at THz frequencies even at room temperature and potentially important for the future design of THz sources. © 1996 American Institute of Physics.
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73.40.Gk Tunneling
73.50.Fq High-field and nonlinear effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Near ultraviolet luminescence of Be doped GaN grown by reactive molecular beam epitaxy using ammonia

A. Salvador, W. Kim, Ö. Aktas, A. Botchkarev, Z. Fan, and H. Morkoç

Appl. Phys. Lett. 69, 2692 (1996); http://dx.doi.org/10.1063/1.117680 (3 pages) | Cited 21 times

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Be doped GaN films grown by reactive molecular beam epitaxy (MBE) are investigated. The room temperature photoluminescence spectrum of the films that were studied shows features in the 390–420 nm range, similar to those observed in Mg doped GaN films, and indicates that Be can form acceptor states about 250 meV above the valence band of GaN. This is in contrast to previous works on GaN:Be films where the only luminescence feature seen was a broad peak centered at 2.16 eV (560 nm). Hot probe measurement indicates p‐type conduction for GaN:Be doped films without any postgrowth annealing. Current–voltage measurements of fabricated mesas of MBE grown layers, consisting of a GaN:Be doped film grown over a Si doped GaN layer, show p–n diodelike rectification. A weak electroluminescence at 380–390 nm is observed when the device is driven with a pulsed current of 600 mA. © 1996 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
85.60.Jb Light-emitting devices

Atomic hydrogen cleaning of GaSb(001) surfaces

G. R. Bell and C. F. McConville

Appl. Phys. Lett. 69, 2695 (1996); http://dx.doi.org/10.1063/1.117681 (3 pages) | Cited 3 times

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We show that the (001) surface of GaSb can be cleaned efficiently by exposure to atomic hydrogen at substrate temperatures in the range 400–470 °C. This treatment removes carbon and oxygen contamination, leaving a clean, ordered surface with a symmetric (1×3) reconstruction after a total H2 dose of approximately 150 kL. An ordered but partially oxidized surface is generated during cleaning, and the removal of this residual oxide is the most difficult part of the process. Auger electron spectroscopy and low energy electron diffraction were used to monitor the chemical cleanliness and the ordering of the surface during the cleaning process, whereas high resolution electron energy loss spectroscopy was used to probe the electronic structure in the near‐surface region. The results obtained indicates that this cleaning procedure leaves no residual electronic damage in the near‐surface region of the Te‐doped (n∼5×1017 cm−3) samples of GaSb(001) studied. © 1996 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
68.35.Dv Composition, segregation; defects and impurities
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
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