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8 Apr 2002

Volume 80, Issue 14, pp. 2433-2611

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Microscopic structure and optical properties of GaAs1−xNx/GaAs(001) interface grown by metalorganic vapor phase epitaxy

H. Dumont, L. Auvray, Y. Monteil, C. Bondoux, L. Largeau, and G. Patriarche

Appl. Phys. Lett. 80, 2460 (2002); http://dx.doi.org/10.1063/1.1468272 (3 pages) | Cited 4 times

Online Publication Date: 2 April 2002

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We have investigated the structure and optical properties of GaAs0.97N0.03/GaAs produced by metalorganic vapor phase epitaxy grown on GaAs surface at 520–550 °C. Using cross-sectional transmission electron microscopy and photoluminescence spectroscopy (PL), we show the presence of a 5–6-nm-thick nitrogen-rich interfacial region. The nitrogen composition near the interface is twice higher (x = 0.038) than that of the bulk epilayer (x = 0.016). PL data shows two peaks located at 1.05 and 1.18 eV associated to the interfacial region and the bulk layer, respectively. We discuss several mechanisms of surface enrichment of nitrogen that occurred during the first stage of GaAsN growth. © 2002 American Institute of Physics.
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68.35.Ct Interface structure and roughness
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
68.35.Dv Composition, segregation; defects and impurities
78.55.Cr III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.37.Lp Transmission electron microscopy (TEM)
68.55.A- Nucleation and growth

Effect of film thickness on hydrogenated amorphous silicon grown with hydrogen diluted silane

P. Danesh, B. Pantchev, D. Grambole, and B. Schmidt

Appl. Phys. Lett. 80, 2463 (2002); http://dx.doi.org/10.1063/1.1467705 (3 pages) | Cited 12 times

Online Publication Date: 2 April 2002

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Thin films of hydrogenated amorphous silicon (a-Si:H) prepared by plasma-enhanced chemical vapor deposition with 10% SiH4 in hydrogen have been studied concerning the effect of film thickness on the hydrogen concentration, interconnected void network and mechanical stress. The hydrogen concentration was determined by nuclear reaction analysis. The interconnected void network was studied by the method of ion exchange in glass substrate. The films were prepared at a substrate temperature in the range of 150–270 °C. The results show that at the substrate temperature of 150 °C the film starts to grow with an extensive void network, and its structural improvement with thickness is manifested by an increase of the film density. In contrast, at 270 °C the film starts to grow with a dense structure, and its improvement is manifested by an increase of the intrinsic compressive stress. The hydrogen concentration does not depend on the film thickness at any substrate temperature. © 2002 American Institute of Physics.
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81.05.Gc Amorphous semiconductors
52.77.Dq Plasma-based ion implantation and deposition
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.43.Dq Amorphous semiconductors, metals, and alloys
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.60.Bs Mechanical and acoustical properties
81.05.Cy Elemental semiconductors
82.80.-d Chemical analysis and related physical methods of analysis
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

High-frequency dispersion of ultrasonic velocity and attenuation of single-crystal 0.72 Pb(Mg1/3Nb2/3)O3–0.28 PbTiO3 with engineered domain structures

Wenhua Jiang, Wenwu Cao, and Pengdi Han

Appl. Phys. Lett. 80, 2466 (2002); http://dx.doi.org/10.1063/1.1468265 (3 pages) | Cited 6 times

Online Publication Date: 2 April 2002

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Using ultrasonic spectroscopy, the frequency dispersions of ultrasonic velocity and attenuation were measured for single crystal 0.72 Pb(Mg1/3Nb2/3)−0.28 PbTiO3 (PMN−28%PT) with engineered domain structures in the frequency range of 50–110 MHz. We found that the velocity dispersion and attenuation are very small for the longitudinal wave propagating along [001] of the pseudotetragonal state. Our results imply that the developed domain-engineered PMN-PT single crystals, which have extremely large d33 and k33, have great potential for high-frequency applications. © 2002 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
62.65.+k Acoustical properties of solids
77.80.Dj Domain structure; hysteresis

Mg-rich precipitates in the p-type doping of InGaN-based laser diodes

M. Hansen, L. F. Chen, S. H. Lim, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 80, 2469 (2002); http://dx.doi.org/10.1063/1.1467704 (3 pages) | Cited 22 times

Online Publication Date: 2 April 2002

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Uniformly distributed precipitates have been observed by transmission electron microscopy in the p-type layers of laser structures. The precipitate density decreases with decreasing flow of biscyclopentadienyl-magnesium (Cp2Mg), and the hole concentration in the laser structure was higher for a lower precipitate density. The higher hole concentration reduces the threshold current density and improves the internal quantum efficiency of the laser because of the higher number of holes available for radiative recombination. The lasers with higher precipitate density also exhibit a higher resistance. The threshold voltage was reduced 30% from 20.8 V for lasers with a high precipitate density to 14.3 V for lasers with a lower precipitate density due to the lower resistance. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
64.75.-g Phase equilibria
61.72.uj III-V and II-VI semiconductors

Si-doped cubic GaN grown on a Si(001) substrate with a thin flat SiC buffer layer

D. Wang, S. Yoshida, and M. Ichikawa

Appl. Phys. Lett. 80, 2472 (2002); http://dx.doi.org/10.1063/1.1467971 (3 pages) | Cited 3 times

Online Publication Date: 2 April 2002

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Highly Si-doped cubic GaN films were grown on a Si(001) substrate coated with a 2.5-nm-thick flat 3C–SiC buffer layer. The Si doping concentration ranged from 1×1019 to 1×1021 cm−3. Upon Si doping, the initial nucleations easily coalesced, producing a flat surface with a 4×1 reconstruction and preferential growth in the [110] direction. The density of stacking faults also increased. The substitution of Ga atoms with Si atoms and the increased density of stacking faults help to relieve the compressive stress in GaN caused by the lattice mismatch of the GaN film and the substrate. GaN showed a strong photoluminescence intensity at room temperature. © 2002 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
68.60.Bs Mechanical and acoustical properties
61.72.S- Impurities in crystals
61.72.Nn Stacking faults and other planar or extended defects
68.35.B- Structure of clean surfaces (and surface reconstruction)

Effect of H2 on nitrogen incorporation in the metalorganic chemical vapor deposition of GaAs1−yNy (0 ⩽ y ⩽ 0.08)

B. F. Moody, P. T. Barletta, N. A. El-Masry, J. C. Roberts, M. E. Aumer, S. F. LeBoeuf, and S. M. Bedair

Appl. Phys. Lett. 80, 2475 (2002); http://dx.doi.org/10.1063/1.1464225 (3 pages) | Cited 3 times

Online Publication Date: 2 April 2002

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The effect of hydrogen on the incorporation of nitrogen in GaAs1−yNy grown by metalorganic chemical vapor deposition (MOCVD) is reported. Nitrogen content as high as y = 0.081 has been achieved when the use of H2 is completely avoided in the MOCVD growth of GaAs1−yNy. When H2 is added to the growth ambient, the value of y in GaAs1−yNy decreases as the relative percent of H2 in the carrier gas increases. We will report on the properties of these GaAsN films and discuss the nature of the effect that H2 has on modulating the N content in these films. © 2002 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase

ZrNbCuNiAl bulk metallic glass matrix composites containing dendritic bcc phase precipitates

U. Kühn, J. Eckert, N. Mattern, and L. Schultz

Appl. Phys. Lett. 80, 2478 (2002); http://dx.doi.org/10.1063/1.1467707 (3 pages) | Cited 153 times

Online Publication Date: 2 April 2002

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We report on phase formation of a multicomponent Zr66.4Nb6.4Cu10.5Ni8.7Al8 glass-forming alloy upon copper mold casting. A bcc phase embedded in a glassy matrix forms for moldcast bulk samples yielding an in-situ bulk metallic glass matrix composite upon slow cooling from the melt. Upon annealing, the first exothermic transformation of the material is related to precipitation of an icosahedral phase from the glassy matrix. The formation of the bcc phase-containing metallic glass composite is strongly governed by the alloy composition and the actual cooling rate during solidification. Room-temperature compression tests reveal significant yielding and plastic deformation before failure. © 2002 American Institute of Physics.
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61.43.Fs Glasses
81.30.Mh Solid-phase precipitation
62.20.F- Deformation and plasticity
81.40.Gh Other heat and thermomechanical treatments
64.75.-g Phase equilibria
81.40.Lm Deformation, plasticity, and creep
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.44.Br Quasicrystals

Strain-induced anisotropic Ge diffusion in SiGe/Si superlattices

Y. S. Lim, J. Y. Lee, H. S. Kim, and D. W. Moon

Appl. Phys. Lett. 80, 2481 (2002); http://dx.doi.org/10.1063/1.1465500 (3 pages) | Cited 5 times

Online Publication Date: 2 April 2002

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Anisotropic diffusion of Ge induced by nonuniform strain in SiGe/Si interfaces in the range of 700–850 °C is directly observed with medium-energy ion-scattering spectroscopy through its composition and strain profiles of atomic-layer depth resolution. For SiGe/Si interfaces with identical composition profiles but with different strain distributions, the anisotropic diffusion of Ge can be clearly correlated with the anisotropic relaxation of the nonuniform strain in the near-surface layer of several nm depth. The results suggest that atomic-scale strain control is critical to maintain abrupt SiGe/Si interfaces under thermal budget. © 2002 American Institute of Physics.
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68.65.Cd Superlattices
68.35.Fx Diffusion; interface formation
68.35.Ct Interface structure and roughness
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Phonon wave-packet dynamics at semiconductor interfaces by molecular-dynamics simulation

P. K. Schelling, S. R. Phillpot, and P. Keblinski

Appl. Phys. Lett. 80, 2484 (2002); http://dx.doi.org/10.1063/1.1465106 (3 pages) | Cited 55 times

Online Publication Date: 2 April 2002

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We directly observe phonon wave packets of well-defined frequency and polarization scattering at a coherent semiconductor interface using molecular-dynamics simulations. We find that in the low-frequency limit the transmission coefficients of both longitudinal and transverse acoustic phonons agree well with those predicted by the continuum-level based acoustic mismatch model. However, the transmission coefficients rapidly decrease close to the cutoff frequency, a result that can be understood within a simple one-dimensional discrete atomic-chain model. We also find that the transmission coefficient for transverse acoustic phonons depends strongly on the relative orientation of the polarization and the Si–Si bonds in the diamond lattice structure. © 2002 American Institute of Physics.
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68.35.Ja Surface and interface dynamics and vibrations

Interaction of electron and hole plasma with coherent longitudinal optical phonons in GaAs

Y.-M. Chang

Appl. Phys. Lett. 80, 2487 (2002); http://dx.doi.org/10.1063/1.1466535 (3 pages) | Cited 13 times

Online Publication Date: 2 April 2002

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The interaction of photoexcited electron–hole plasma with impulsively excited coherent longitudinal optical phonons in GaAs was investigated via time-resolved second-harmonic generation. The dephasing time of coherent LO phonons reduces significantly as photoexcited electron–hole plasma is injected into the near-surface depletion region. The coherent LO-electron and LO-hole coupling modes can both be clearly observed and investigated in real time. The rapid dephasing of the coherent LO-hole coupling mode is attributed to the strong polar phonon-carrier interaction and the overdamped nature of hole plasma. © 2002 American Institute of Physics.
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63.20.K- Phonon interactions
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.47.-p Spectroscopy of solid state dynamics
72.30.+q High-frequency effects; plasma effects
72.80.Ey III-V and II-VI semiconductors

Normal-incidence voltage-tunable middle- and long-wavelength infrared photoresponse in self-assembled InAs quantum dots

Zhonghui Chen, Eui-Tae Kim, and Anupam Madhukar

Appl. Phys. Lett. 80, 2490 (2002); http://dx.doi.org/10.1063/1.1467974 (3 pages) | Cited 42 times

Online Publication Date: 2 April 2002

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We report the realization of electron intraband absorption based middle- (∼5.6 μm) and long- (∼10 μm) wavelength infrared (IR) photoresponse for normally incident radiation on InGaAs-capped GaAs(001)/InAs quantum dots (QDs) in a n–i(QD)–n structure. The relative photoresponse in this dual-wavelength structure is tunable up to two orders of magnitude with bias. The full width at half maximum of the long-wavelength IR intraband photocurrent peak at 80 K is as narrow as 8.2 meV. © 2002 American Institute of Physics.
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81.07.Ta Quantum dots
72.40.+w Photoconduction and photovoltaic effects
73.63.Kv Quantum dots
73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
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