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4 Aug 2003

Volume 83, Issue 5, pp. 817-1056

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 611 (2003); http://dx.doi.org/10.1063/1.1595724 (3 pages)

Chung-Chih Wu, Chieh-Wei Chen, and Ting-Yi Cho
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Photoluminescence in tensile-strained Si type-II quantum wells on bulk single-crystal SiGe substrates

S. R. Sheng, N. L. Rowell, and S. P. McAlister

Appl. Phys. Lett. 83, 857 (2003); http://dx.doi.org/10.1063/1.1597413 (3 pages) | Cited 4 times

Online Publication Date: 30 July 2003

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Near-band edge photoluminescence (PL) in high-quality tensile-strained Si type-II quantum wells (QWs) with varying well width grown on bulk crystal SiGe substrates by using ultrahigh vacuum chemical vapor deposition has been studied. In contrast to the blueshifts observed in the PL lines of Si1−xGex QWs on Si, the PL lines of Si QWs exhibit redshifts with increasing excitation density. The PL from the SiGe substrate shows no such shift. The excitation-induced PL redshifts decrease as the well width decreases, and are essentially independent of temperature up to 15 K. The rapid thermal annealing (RTA) was found to improve the crystal quality of the samples. RTA enhances the integrated PL intensity, results in narrowing and blueshifting of PL bands at a given excitation density, and reduces the exponent in the excitation power dependence as well as the amount of excitation-induced PL redshifting. Possible mechanisms for the observed excitation-induced PL redshifts were examined, including band bending, band filling, and binding of excitons to impurities. © 2003 American Institute of Physics.
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78.55.Ap Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing
78.67.De Quantum wells
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Atomic arrangement at the AlN/Si (111) interface

R. Liu, F. A. Ponce, A. Dadgar, and A. Krost

Appl. Phys. Lett. 83, 860 (2003); http://dx.doi.org/10.1063/1.1597749 (3 pages) | Cited 36 times

Online Publication Date: 30 July 2003

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High-quality GaN epilayers have been grown on Si (111) substrates by metalorganic vapor phase epitaxy using a low-temperature AlN nucleation layer. The atomic arrangement at the epilayer/substrate interface has been investigated by high-resolution electron microscopy. A crystallographically abrupt interface is observed along most of the epilayer, indicating that the AlN/Si interface is thermodynamically stable and of high crystalline quality. Lattice images at the interface show a periodic array of misfit dislocations. The lattice images have been analyzed in detail in order to obtain information about the atomic arrangement, and interface bonding models are proposed. © 2003 American Institute of Physics.
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68.35.Ct Interface structure and roughness
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.
81.15.Kk Vapor phase epitaxy; growth from vapor phase

A critical examination of the P–h2 relationship in nanoindentation

M. Troyon and M. Martin

Appl. Phys. Lett. 83, 863 (2003); http://dx.doi.org/10.1063/1.1596384 (3 pages) | Cited 8 times

Online Publication Date: 30 July 2003

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In this letter we derive a corrected analytical expression for the indentation load–depth relation during loading in an indentation experiment; P = Er(1/mathmath+ε(m)/γmathmath)−2(h+hb)2. This expression takes into account the correction factor γ in the fundamental relations among contact stiffness, elastic modulus, and contact area, which is frequently forgotten in the literature, and the exact value of the geometric constant ε(m) of the indenter. A comparison with previously used expressions shows a much better agreement between hardness measurements from loading and unloading curve analyses. © 2003 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
62.20.D- Elasticity
62.20.Qp Friction, tribology, and hardness
81.40.Jj Elasticity and anelasticity, stress-strain relations

Investigation of radiative recombination from Mn-related states in Ga1−xMnxAs

F. J. Teran, L. X. Zhao, A. Patanè, R. P. Campion, C. T. Foxon, L. Eaves, and B. L. Gallagher

Appl. Phys. Lett. 83, 866 (2003); http://dx.doi.org/10.1063/1.1597750 (3 pages) | Cited 4 times

Online Publication Date: 30 July 2003

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We show that the incorporation of a Ga1−xMnxAs layer with x = 1% in the intrinsic region of a p–i–n diode produces an intense electroluminescence signal due to electronic transitions that involve holes bound to Mn-related states. The intensity of the electroluminescence signal is weakly affected by the temperature over the range of 5–290 K, thus indicating that the Mn-related hole states act as efficient sites for radiative recombination even at room temperature, despite the strong disorder in the Ga1−xMnxAs at relatively high values of x. © 2003 American Institute of Physics.
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78.60.Fi Electroluminescence
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Eq III-V semiconductors
75.50.Pp Magnetic semiconductors
85.30.Kk Junction diodes

Comparison of Cu electromigration lifetime in Cu interconnects coated with various caps

C.-K. Hu, L. Gignac, E. Liniger, B. Herbst, D. L. Rath, S. T. Chen, S. Kaldor, A. Simon, and W.-T. Tseng

Appl. Phys. Lett. 83, 869 (2003); http://dx.doi.org/10.1063/1.1596375 (3 pages) | Cited 30 times

Online Publication Date: 30 July 2003

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Electromigration in Cu Damascene lines with bamboo-like grain structures, either capped with Ta/TaN, SiNx, SiCxNyHz layers, or without any cap, was investigated. A thin Ta/TaN cap on top of the Cu line surface significantly improves electromigration lifetime when compared with lines without a cap and with lines capped with SiNx or SiCxNyHz. The activation energy for electromigration increased from 0.87 eV for lines without a cap to 1.0–1.1 eV for samples with SiNx or SiCxNyHz caps and to 1.4 eV for Ta/TaN capped samples. © 2003 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration

Strain analysis of a quantum-wire system produced by cleaved edge overgrowth using grazing incidence x-ray diffraction

M. Sztucki, T. U. Schülli, T. H. Metzger, V. Chamard, R. Schuster, and D. Schuh

Appl. Phys. Lett. 83, 872 (2003); http://dx.doi.org/10.1063/1.1597962 (3 pages) | Cited 2 times

Online Publication Date: 30 July 2003

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A GaAs surface layer of 10 nm thickness was grown on the cleaved edge of an In0.1Al0.9As/Al0.33Ga0.67As multilayer in order to induce a lateral periodic strain modulation. We apply surface sensitive grazing incidence x-ray diffraction to distinguish between compositional/morphological and purely strain induced modulations. The experimentally determined strain profile is confirmed by finite-element model calculations. The GaAs layer is found to be purely strain modulated with an average lattice parameter change of (0.8±0.1)% with respect to relaxed GaAs. © 2003 American Institute of Physics.
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68.65.La Quantum wires (patterned in quantum wells)
81.07.Vb Quantum wires
61.05.cm X-ray reflectometry (surfaces, interfaces, films)

Effect of rapid thermal annealing on strain in ultrathin strained silicon on insulator layers

T. S. Drake, C. Ní Chléirigh, M. L. Lee, A. J. Pitera, E. A. Fitzgerald, D. A. Antoniadis, D. H. Anjum, J. Li, R. Hull, N. Klymko, and J. L. Hoyt

Appl. Phys. Lett. 83, 875 (2003); http://dx.doi.org/10.1063/1.1598649 (3 pages) | Cited 24 times

Online Publication Date: 30 July 2003

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The fabrication of ultrathin strained silicon directly on insulator is demonstrated and the thermal stability of these films is investigated. Ultrathin ( ∼ 13 nm) strained silicon on insulator layers were fabricated by epitaxial growth of strained silicon on relaxed SiGe, wafer bonding, and an etch-back technique employing two etch-stop layers for improved across wafer thickness uniformity. Using 325 nm Raman spectroscopy, no strain relaxation is observed following rapid thermal annealing of these layers to temperatures as high as 950 °C. The thermal stability of these films is promising for the future fabrication of enhanced performance strained Si ultrathin body and double-gate metal-oxide-semiconductor field-effect transistors. © 2003 American Institute of Physics.
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78.30.Hv Other nonmetallic inorganics
61.72.Cc Kinetics of defect formation and annealing
68.60.Bs Mechanical and acoustical properties
85.30.Tv Field effect devices

Mg acceptor level in AlN probed by deep ultraviolet photoluminescence

K. B. Nam, M. L. Nakarmi, J. Li, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 83, 878 (2003); http://dx.doi.org/10.1063/1.1594833 (3 pages) | Cited 37 times

Online Publication Date: 30 July 2003

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Mg-doped AlN epilayers were grown by metalorganic chemical vapor deposition on sapphire substrates. Deep UV picosecond time-resolved photoluminescence (PL) spectroscopy has been employed to study the optical transitions in Mg-doped AlN epilayers. From PL emission spectra and the temperature dependence of the PL emission intensity, a binding energy of 0.51 eV for Mg acceptor in AlN was determined. Together with previous experimental results, the Mg acceptor activation energy in AlxGa1−xN as a function of the Al content (x) was extrapolated for the entire AlN composition range. The average hole effective mass in AlN was also deduced to be about 2.7 m0 from the experimental value of the Mg binding energy together with the use of the effective mass theory. © 2003 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.47.-p Spectroscopy of solid state dynamics
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance
73.50.Dn Low-field transport and mobility; piezoresistance
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Photochromic effect in magnesium-doped α-Al2O3 single crystals

M. Tardío, R. Ramírez, R. González, Y. Chen, and M. R. Kokta

Appl. Phys. Lett. 83, 881 (2003); http://dx.doi.org/10.1063/1.1597963 (3 pages) | Cited 5 times

Online Publication Date: 30 July 2003

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A reversible photochromic effect was investigated in Mg-doped α-Al2O3 single crystals oxidized at elevated temperatures. Alternate illumination with blue and UV light at T ⩽ 210 K results in reversible disappearance and reappearance of a gray-purple coloration, respectively. The coloration can also be fully rejuvenated by warming the crystal to T ≥ 215 K. © 2003 American Institute of Physics.
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78.20.-e Optical properties of bulk materials and thin films

Thermal oxidation of (0001) 4H-SiC at high temperatures in ozone-admixed oxygen gas ambient

Ryoji Kosugi, Kenji Fukuda, and Kazuo Arai

Appl. Phys. Lett. 83, 884 (2003); http://dx.doi.org/10.1063/1.1598621 (3 pages) | Cited 3 times

Online Publication Date: 30 July 2003

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The method of oxidation by atomic oxygen has been developed for gate oxide formation in SiC metal–oxide–semiconductor (MOS) devices. Ozone (O3)–admixed oxygen (O2) gas is introduced into the cold-wall oxidation furnace, where atomic oxygen in a ground state is formed by thermal decomposition of O3 molecules at elevated sample temperatures. The growth rate of oxide in the O3-admixed gas shows a maximum at around 666.4 Pa and 950–1200 °C, whereas the rate in pure O2 gas is negligible below 6664.5 Pa. Interface trap density (Dit) of the MOS capacitors fabricated using atomic oxygen strongly depends on the oxidization temperature; oxidation at 1200 °C results in significant reduction of Dit in comparison with that at 950 °C. © 2003 American Institute of Physics.
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81.65.Mq Oxidation
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.20.Pm Rate constants, reaction cross sections, and activation energies

Optical and structural anisotropy of InP/GaInP quantum dots for laser applications

Y. M. Manz, A. Christ, O. G. Schmidt, T. Riedl, and A. Hangleiter

Appl. Phys. Lett. 83, 887 (2003); http://dx.doi.org/10.1063/1.1598290 (3 pages) | Cited 8 times

Online Publication Date: 30 July 2003

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Self-assembled InP quantum dots, embedded in Ga0.52In0.48P and grown by solid source molecular-beam epitaxy, exhibit strong structural and optical anisotropy. Photoluminescence measurements reveal that the quantum dots are elongated in [1math0] crystal direction and the optical transitions of both the dots and the surrounding GaInP material dominate for light polarized along this direction, whereas embedded compressively strained GaxIn1−xP quantum wells behave isotropically. The comparison of the optical gain of a strained GaxIn1−xP quantum well laser and a threefold stacked quantum-dot laser in [110] and [1math0] directions (edge emission) emphasizes this difference. The gain of the quantum-well laser shows no directional dependence. The quantum-dot laser reveals significantly larger gain for light propagating perpendicular to the dot elongation. Thus, particular care has to be taken to align the cavities of InP/GaInP quantum-dot lasers in [110] direction. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.67.Hc Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.55.Cr III-V semiconductors

Lattice parameter and energy band gap of cubic AlxGayIn1−x−yN quaternary alloys

M. Marques, L. K. Teles, L. M. R. Scolfaro, J. R. Leite, J. Furthmüller, and F. Bechstedt

Appl. Phys. Lett. 83, 890 (2003); http://dx.doi.org/10.1063/1.1597986 (3 pages) | Cited 28 times

Online Publication Date: 30 July 2003

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First-principles total energy calculations, combined with a generalized quasichemical approach to disorder and compositional effects, are used to obtain the lattice parameter and the energy band gap of cubic AlxGayIn1−x−yN quaternary alloys. It is found that the lattice parameter a(x,y) fulfills a Vegard’s-like law; that is, it shows a linear dependence on the alloy contents x and y. The range of compositions for which the alloy is lattice-matched to GaN is obtained. The energy band gap Eg(x,y) of the quaternary alloy deviates from a planar behavior displaying a two-dimensional gap bowing in the x–y plane. Analytical expressions that fit the calculated a(x,y) and Eg(x,y) surfaces are derived in order to provide ready access to the lattice parameter and energy band gap of the alloy for the entire range of compositions. The results are compared with data for the wurtzite phase alloys. © 2003 American Institute of Physics.
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71.20.Nr Semiconductor compounds
61.66.Fn Inorganic compounds
71.15.Nc Total energy and cohesive energy calculations

Retrieval of the complex permittivity of spherical nanoparticles in a liquid host material from a spectral surface plasmon resonance measurement

Jarkko J. Saarinen, Erik M. Vartiainen, and Kai-Erik Peiponen

Appl. Phys. Lett. 83, 893 (2003); http://dx.doi.org/10.1063/1.1598288 (3 pages) | Cited 10 times

Online Publication Date: 30 July 2003

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A method for obtaining the complex permittivity of a Maxwell Garnett liquid with the aid of spectral surface plasmon resonance spectroscopy is presented. The Maxwell Garnett liquid is assumed to consist of small absorbing spherical inclusions in a host liquid. It is shown that the permittivity of the inclusions can be calculated if the optical constants of the host liquid are known. It is believed that such a method will gain increasing importance in the analysis of biological reactions. © 2003 American Institute of Physics.
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77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.46.-w Structure of nanoscale materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Domain of CuPtB-type and CuAu–I-type ordered structures in highly strained CdxZn1−xTe/ZnTe heterostructures

H. S. Lee, J. Y. Lee, T. W. Kim, and H. L. Park

Appl. Phys. Lett. 83, 896 (2003); http://dx.doi.org/10.1063/1.1599966 (3 pages) | Cited 3 times

Online Publication Date: 30 July 2003

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The ordered behaviors in highly strained CdxZn1−xTe/ZnTe epitaxial layers grown on (001) GaAs substrates were investigated by using selected area electron diffraction pattern (SADP) and cross-sectional high-resolution transmission electron microscopy (HRTEM) measurements. The results of the SADP and the HRTEM measurements showed that CuPt– and CuAu–I-type ordered structures were formed in the CdxZn1−xTe epitaxial layers. TEM images showed that the sizes of the ordered domains with elliptical shapes ranged between approximately 10 and 80 nm. An epitaxial relationship between the CuPt– and CuAu–I-type ordered structures was observed. The coexisting behaviors of the two ordered structures and the epitaxial relationship between the structures are discussed. The present results can help to improve the understanding of the formation mechanism and the coexisting behaviors of the two ordered structures in CdxZn1−xTe epilayers. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.37.Lp Transmission electron microscopy (TEM)

Structure and bulk modulus of M2AlC (M=Ti, V, and Cr)

Zhimei Sun, Rajeev Ahuja, Sa Li, and Jochen M. Schneider

Appl. Phys. Lett. 83, 899 (2003); http://dx.doi.org/10.1063/1.1599038 (3 pages) | Cited 87 times

Online Publication Date: 30 July 2003

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We have performed theoretical studies of the bulk modulus of M2AlC, where M=Ti, V, Cr by means of ab initio total energy calculations using the projector augmented wave methods. Our estimated equilibrium volume and the lattice parameters (c/a) agree well (within ±2% and ±0.06%, respectively) with experimental data. The bulk modulus of M2AlC increases as Ti is substituted with V and Cr by 19% and 36%, respectively. This can be understood since the substitution of Ti by V and Cr is associated with an extensive increase in the M–Al and M–C bond energy. © 2003 American Institute of Physics.
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62.20.D- Elasticity
61.66.Fn Inorganic compounds
61.50.Lt Crystal binding; cohesive energy

Transition from three- to two-dimensional growth in strained SrRuO3 films on SrTiO3(001)

F. Sánchez, M. V. García-Cuenca, C. Ferrater, M. Varela, G. Herranz, B. Martínez, and J. Fontcuberta

Appl. Phys. Lett. 83, 902 (2003); http://dx.doi.org/10.1063/1.1599040 (3 pages) | Cited 17 times

Online Publication Date: 30 July 2003

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The morphology of strained SrRuO3 films grown on SrTiO3(001) has been investigated as a function of thickness. A transition of growth mode has been observed. At the early stages, there is a fingerlike structure originated by three-dimensional (3D) islands that nucleated along the substrate steps. Afterward, adatoms stick preferentially in the valleys of the structure and the films become progressively smoother. At a thickness above 10–20 nm, the films are extremely flat and have a self-organized structure of terraces and steps, with the growth proceeding mainly by a step flow (two-dimensional) mechanism. Relevance on film properties and possible use of the initial, nanometric, 3D structures are discussed. © 2003 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)
68.60.Bs Mechanical and acoustical properties
68.37.Ps Atomic force microscopy (AFM)

Investigation of boron diffusion in 6H-SiC

Y. Gao, S. I. Soloviev, and T. S. Sudarshan

Appl. Phys. Lett. 83, 905 (2003); http://dx.doi.org/10.1063/1.1598622 (3 pages) | Cited 13 times

Online Publication Date: 30 July 2003

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p-type doping of 6H-SiC was implemented by diffusion of boron at temperatures higher than 1900 °C. The doping profiles were clearly divided into steep (zone I) and long-tail (zone II) regions. The boron diffusions in both regions are well fitted by erfc functions but with different diffusion coefficients, which are an activation energy (EA) of 6.1 eV and a prefactor (D0) of 3.2 cm2/s for zone I and 4.6 eV and 0.1 cm2/s for zone II, respectively. Further, it has been confirmed that the boron acceptors in zone I are primarily located at shallow energy levels ( ∼ 300 meV) and the ones in zone II are located at deep energy levels ( ∼ 700 meV). © 2003 American Institute of Physics.
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61.72.up Other materials
71.55.Ht Other nonmetals
66.30.J- Diffusion of impurities
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