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22 Nov 2004

Volume 85, Issue 21, pp. 4831-5106

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 4845 (2004); http://dx.doi.org/10.1063/1.1823019 (3 pages)

Wounjhang Park and Jeong-Bong Lee
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First-principles calculations of the mean inner Coulomb potential for sphalerite type II–VI semiconductors

M. Schowalter, D. Lamoen, A. Rosenauer, P. Kruse, and D. Gerthsen

Appl. Phys. Lett. 85, 4938 (2004); http://dx.doi.org/10.1063/1.1823598 (3 pages) | Cited 6 times

Online Publication Date: 23 November 2004

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The mean inner Coulomb potential (MIP) of ZnS, CdS, ZnSe, CdSe, ZnTe, and CdTe has been calculated for a (110) slab geometry by the full potential linearized augmented plane-wave (FLAPW) method using both the local density approximation (LDA) and a generalized gradient approximation (GGA) for the exchange and correlation part of the potential. Typical differences between values calculated within the LDA and the GGA are smaller than typical experimental error bars in literature. We use experimental and self-consistently calculated lattice parameters for the calculation of the MIP. Values calculated for ZnS are compared with experimental values.
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71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Can correlated substitution enhance the Curie temperature in diluted magnetic semiconductors?

Georges Bouzerar, Timothy Ziman, and Josef Kudrnovský

Appl. Phys. Lett. 85, 4941 (2004); http://dx.doi.org/10.1063/1.1826226 (3 pages) | Cited 27 times

Online Publication Date: 23 November 2004

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We present a quantitative theory for ferromagnetism in diluted magnetic semiconductors under the assumption that the positions of the substitutional magnetic impurities are correlated. The theory predicts that room-temperature ferromagnetism should be possible in macroscopically homogeneous samples of MnxGa1−xAs if the probability of pairs of Mn impurities on neighboring Ga sites is sufficiently enhanced. The theory predicts similar increases in the Curie temperatures for MnxGa1−xN but the temperatures remain lower than in MnxGa1−xAs.
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75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.10.-b General theory and models of magnetic ordering
61.72.S- Impurities in crystals
75.30.Hx Magnetic impurity interactions

Plasma hydrogenation of strain-relaxed SiGe∕Si heterostructure for layer transfer

Peng Chen, Paul K. Chu, T. Höchbauer, M. Nastasi, D. Buca, S. Mantl, N. David Theodore, T. L. Alford, J. W. Mayer, R. Loo, M. Caymax, M. Cai, and S. S. Lau

Appl. Phys. Lett. 85, 4944 (2004); http://dx.doi.org/10.1063/1.1824171 (3 pages) | Cited 2 times

Online Publication Date: 23 November 2004

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The use of plasma hydrogenation for relaxed SiGe layer transfer is demonstrated. It is found that the interface of a strain-relaxed SiGe∕Si heterostructure is effective in trapping H during plasma hydrogenation. Long microcracks observed at the interface due to the trapping of indiffused H indicate the distinct possibility of transferring the overlayer using the ion-cutting technique. Our results suggest that interfacial defects induced by the He implantation relaxation process trap the indiffusing H atoms and lead to interfacial cracks during hydrogenation or upon postannealing at higher temperatures. It is further noted that trapping of H at the interface is possible only in strain-relaxed structures. Without strain relaxation, H atoms introduced by plasma hydrogenation get trapped just below the sample surface and form a band of shallow platelets. Without the need for high-dose high-energy ion implantation, our results suggest an effective way for high-quality strain-relaxed SiGe layer transfer. The technique has potential for application in the fabrication of SiGe-on-insulator strained Si epitaxial layer and related structures.
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81.65.-b Surface treatments
52.77.Dq Plasma-based ion implantation and deposition
68.35.Gy Mechanical properties; surface strains
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.72.Cc Kinetics of defect formation and annealing
61.72.uf Ge and Si
61.72.up Other materials
68.35.Ct Interface structure and roughness

Evidence of Si∕SiGe heterojunction roughness scattering

C. W. Liu, M. H. Lee, Y. C. Lee, P. S. Chen, C.-Y. Yu, J.-Y. Wei, and S. Maikap

Appl. Phys. Lett. 85, 4947 (2004); http://dx.doi.org/10.1063/1.1828224 (3 pages) | Cited 2 times

Online Publication Date: 23 November 2004

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The separation distance between the electron channel at oxide∕Si interface and the strained-Si∕relaxed-SiGe heterojunction can significantly affect the effective electron mobility of metal–oxide–silicon field-effect transistors due to the roughness scattering of the underneath Si∕SiGe heterojunction. The mobility degradation due to the Si∕SiGe heterojunction with the roughness of 7 nm becomes insignificant when the strained-Si thickness is larger than ∼20 nm. A clear hole confinement shoulder is observed in the accumulation region of the capacitance–voltage curves, indicating that the abrupt transition from the SiGe buffer to strained Si is maintained at the rough heterojunction. The heterojunction roughness scattering not only degrades the electron mobility, but also degrades the device characteristics such as the transconductance and cut-off frequency.
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85.30.Tv Field effect devices
73.25.+i Surface conductivity and carrier phenomena
68.35.Ct Interface structure and roughness
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.20.Fr Low-field transport and mobility; piezoresistance

Dual role of fluorine at the Si–SiO2 interface

L. Tsetseris, X. J. Zhou, D. M. Fleetwood, R. D. Schrimpf, and S. T. Pantelides

Appl. Phys. Lett. 85, 4950 (2004); http://dx.doi.org/10.1063/1.1825621 (3 pages) | Cited 12 times

Online Publication Date: 23 November 2004

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Fluorine is known to have both a beneficial and adverse role on the characteristics of Si–SiO2-based devices. Here we report the results of first-principles calculations in terms of which we elucidate this dual behavior. On one hand, we find that Si–F interfacial bonds are resistant to depassivation by hydrogen species, with the process being shut down in the presence of holes. However, we also show that any excess of fluorine has a negative effect since it either creates stretched bonds, which can act as carrier traps, or disrupts an abrupt interface by cleavage of Si–Si bonds.
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81.05.Cy Elemental semiconductors
73.20.At Surface states, band structure, electron density of states
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Effect of encapsulation temperature on Si:P δ-doped layers

K. E. J. Goh, L. Oberbeck, M. Y. Simmons, A. R. Hamilton, and R. G. Clark

Appl. Phys. Lett. 85, 4953 (2004); http://dx.doi.org/10.1063/1.1827940 (3 pages) | Cited 18 times

Online Publication Date: 23 November 2004

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We present a systematic study of the effect of encapsulation temperature on dopant segregation and electronic transport in Si:P δ-doped layers. We demonstrate that while limited dopant segregation and complete electrical activation can be achieved at room temperature, a δ-doped layer encapsulated at ∼250°C represents the best compromise between high electrical quality (mobility ∼61 cm2 V−1 s−1 and phase coherence length ∼72 nm at 4.2 K) and minimal dopant segregation. Higher encapsulation temperatures are shown to lead to significant dopant segregation.
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81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Cn Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.S- Impurities in crystals
68.35.Dv Composition, segregation; defects and impurities
73.61.Cw Elemental semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Dn Low-field transport and mobility; piezoresistance

Efficient p-type doping of GaN films by plasma-assisted molecular beam epitaxy

A. Bhattacharyya, W. Li, J. Cabalu, T. D. Moustakas, David J. Smith, and R. L. Hervig

Appl. Phys. Lett. 85, 4956 (2004); http://dx.doi.org/10.1063/1.1826223 (3 pages) | Cited 15 times

Online Publication Date: 23 November 2004

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In this paper we report on the mechanism of efficient incorporation of Mg in GaN films during growth by plasma-assisted molecular beam epitaxy. It is found that Mg incorporates more efficiently during growth of GaN films at high temperatures (770 °C) under extreme Ga-rich conditions. We propose that this result is due to the dissolution of Mg in the excess Ga on the growth surface and its incorporation into the GaN film via liquid-phase processes. Transport measurements at 300 K together with secondary-ion-mass-spectroscopy indicate that the Mg-doping efficiency of GaN under these conditions of growth is 10%. Using this method of doping, p-type GaN films free of Ga droplets, with hole concentrations varying from 2×1017 to 3×1018 cm−3 and corresponding mobilities varying from 30 to 2 cm2/V s, are obtained. The lowest resistivity achieved is 0.3 Ω cm.
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81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
68.55.A- Nucleation and growth
73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.20.Fr Low-field transport and mobility; piezoresistance
68.55.-a Thin film structure and morphology

Interaction between organic semiconductors and LiF dopant

Y. Yuan, D. Grozea, S. Han, and Z. H. Lu

Appl. Phys. Lett. 85, 4959 (2004); http://dx.doi.org/10.1063/1.1821653 (3 pages) | Cited 22 times

Online Publication Date: 23 November 2004

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X-ray photoemission spectroscopy and optical absorption have been used to study the interaction between LiF dopant and various organic semiconductor hosts including N,N′-diphenyl-N,N′-bis (3-methylphenyl)-1, 1′-biphenyl-4, 4′-diamine (TPD), N,N′-bis (1-naphthyl)-N,N′-diphenyl-1, 1′-biphenyl-4, 4′-diamine (NPB), tris (8-hydroxyquinolinato) aluminum (Alq3), C60, and copper phthalacyanine (CuPc). It was found that there is a charge transfer between host and dopant in the Alq3–LiF and C60–LiF systems, while no such charge transfer was observed for the TPD–LiF, NPB–LiF, and CuPc–LiF systems. The experimental data show that F− anion acts as an n-type donor—donating electron charge to the electron transport molecules.
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79.60.Fr Polymers; organic compounds
79.60.Bm Clean metal, semiconductor, and insulator surfaces
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
78.66.Tr Fullerenes and related materials
78.66.Qn Polymers; organic compounds
78.40.Me Organic compounds and polymers
78.40.Ri Fullerenes and related materials
78.30.Jw Organic compounds, polymers
78.30.Na Fullerenes and related materials

Radiation-induced zero-resistance states with resolved Landau levels

R. G. Mani

Appl. Phys. Lett. 85, 4962 (2004); http://dx.doi.org/10.1063/1.1825066 (3 pages) | Cited 28 times

Online Publication Date: 23 November 2004

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The microwave-photoexcited high mobility GaAs∕AlGaAs two-dimensional electron system exhibits an oscillatory magnetoresistance with vanishing resistance in the vicinity of magnetic fields B=[4∕(4j+1)]Bf, where Bf=2πfm*∕e, m* is an effective mass, e is the charge, f is the microwave frequency, and j=1,2,3… Here, we report transport with well-resolved Landau levels, and some transmission characteristics.
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84.40.-x Radiowave and microwave (including millimeter wave) technology
73.43.-f Quantum Hall effects

Highly resistive annealed low-temperature-grown InGaAs with sub-500 fs carrier lifetimes

C. Baker, I. S. Gregory, W. R. Tribe, I. V. Bradley, M. J. Evans, E. H. Linfield, and M. Missous

Appl. Phys. Lett. 85, 4965 (2004); http://dx.doi.org/10.1063/1.1824179 (3 pages) | Cited 12 times

Online Publication Date: 23 November 2004

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We have optimized low-temperature-grown In0.3Ga0.7As for use in ultrafast photoconductive devices. Using low temperature ex situ annealing techniques, we have produced a photoconductive material that is highly resistive (∼104 Ω cm), has sub-500 fs carrier trapping lifetimes, and is matched to 1.06 μm laser excitation.
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81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.50.Pz Photoconduction and photovoltaic effects
78.47.-p Spectroscopy of solid state dynamics

Probing electrical transport across oxide interfaces by noncontact atomic force microscopy

Rui Shao and Dawn A. Bonnell

Appl. Phys. Lett. 85, 4968 (2004); http://dx.doi.org/10.1063/1.1825634 (3 pages) | Cited 3 times

Online Publication Date: 23 November 2004

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An approach for determining surface potential based on noncontact atomic force microscopy (NC-AFM) has been used to acquire the potential profile of the grain boundary in a 24° 0.05 wt % Nb-doped SrTiO3 bicrystal under lateral bias. The breakdown voltage of the grain boundary is found to be 1.2 V. The current–voltage characteristics obtained from this surface potentiometry have been compared with standard four-point measurement. The exponential dependence of the current on voltage indicates a Schottky-type transport mechanism. In addition, we found that NC-AFM topography is affected by the nonuniform potential distribution across the boundary, and this effect is especially strong at large lateral biases, resulting in a spurious step feature, which implies that true topography of an inhomogeneous surface cannot be obtained without first nullifying electrostatic interaction between tip and sample.
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07.79.Lh Atomic force microscopes
61.72.Mm Grain and twin boundaries
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
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