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3 Apr 2006

Volume 88, Issue 14, Articles (14xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 143508 (2006); http://dx.doi.org/10.1063/1.2191448 (3 pages)

R. Chan, M. Feng, N. Holonyak, A. James, and G. Walter
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Thermomigration in SnPb composite flip chip solder joints

Annie T. Huang, A. M. Gusak, K. N. Tu, and Yi-Shao Lai

Appl. Phys. Lett. 88, 141911 (2006); http://dx.doi.org/10.1063/1.2192694 (3 pages) | Cited 50 times

Online Publication Date: 4 April 2006

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We have used composite flip chip solder joints to study thermomigration. The composite solder joint has 97Pb3Sn on the Si side and eutectic 37Pb63Sn on the substrate side. Redistribution of Sn and Pb occurs in thermomigration, and we found that Sn has moved to the Si side (the hot end) and Pb to the substrate side (the cold end). We estimate the driving force that a temperature gradient of 1000 °C/cm or a temperature difference of 10 °C across a solder joint of 100 μm in diameter is sufficient to induce the thermomigration.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Prismatic stacking faults in epitaxially laterally overgrown GaN

J. Mei, S. Srinivasan, R. Liu, F. A. Ponce, Y. Narukawa, and T. Mukai

Appl. Phys. Lett. 88, 141912 (2006); http://dx.doi.org/10.1063/1.2193352 (3 pages) | Cited 23 times

Online Publication Date: 5 April 2006

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We report on the presence of optically active stacking faults on basal and prismatic planes in epitaxially laterally overgrown GaN (ELOG) on {11math2} facets. The structure of the faults has been analyzed using diffraction contrast electron microscopy. We show that stacking faults on {11math0} prismatic planes involve a lattice displacement of ½〈1math01〉, parallel to the fault plane. They appear as jogs connecting basal-plane stacking faults, the latter with a lattice displacement of ⅙〈20math3〉. These faults are observed only in the laterally overgrown regions that grow on {11math2} planes, which indicates that the stacking fault formation is closely related to the orientation of the growth surface. Possible formation mechanisms of these faults are discussed. Direct correlation between TEM and cathodoluminescence shows that these prismatic-plane and basal-plane stacking faults are optically active with light emission at 3.30 and 3.41 eV, respectively.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
61.72.Nn Stacking faults and other planar or extended defects
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence

Reduced intermolecular interaction in organic ultrathin films

O. D. Gordan, C. Himcinschi, D. R. T. Zahn, C. Cobet, N. Esser, and W. Braun

Appl. Phys. Lett. 88, 141913 (2006); http://dx.doi.org/10.1063/1.2189153 (3 pages) | Cited 5 times

Online Publication Date: 5 April 2006

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Submonolayer sensitivity was achieved using in situ ellipsometry to monitor the evolution of the dielectric function of tris(8-hydroxyquinoline)-aluminum(III) (Alq3) layers from submonolayer coverage to thick bulklike layers. The Alq3 layers were deposited under ultrahigh vacuum conditions onto hydrogen passivated silicon. The characteristic vacuum-ultraviolet (VUV) absorption lines of Alq3 were detected using synchrotron radiation as light source. In such ultrathin films the absorption lines corresponding to molecular transitions of the Alq3 are found to be spectrally blueshifted with respect to bulklike layers. We attribute the shift to the effect of reduced intermolecular interaction in the submonolayer regime.
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78.66.Qn Polymers; organic compounds
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Fy Semiconductors
78.40.Me Organic compounds and polymers

Transient lateral photovoltaic effect in p-n heterojunctions of La0.7Sr0.3MnO3 and Si

Kun Zhao, Kui-juan Jin, Huibin Lu, Yanhong Huang, Qingli Zhou, Meng He, Zhenghao Chen, Yueliang Zhou, and Guozhen Yang

Appl. Phys. Lett. 88, 141914 (2006); http://dx.doi.org/10.1063/1.2193436 (3 pages) | Cited 36 times

Online Publication Date: 5 April 2006

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A transient lateral photovoltaic effect (LPVE) has been observed in p-La0.7Sr0.3MnO3/n-Si heterojunctions. Under the nonuniform irradiation of a pulsed laser, the LPVE shows high sensitivity to the spot position on the La0.7Sr0.3MnO3 surface. A mechanism based on the well established model for the LPVE in conventional semiconductors has been applied to explain the LPVE in the heteroepitaxial junctions of perovskite-type metal oxides. The large LPVE in the heteroepitaxial junctions is expected to make the perovskite-type metal oxide a new and faster candidate for position-sensitive photodetectors.
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73.50.Pz Photoconduction and photovoltaic effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.60.Gz Photodetectors (including infrared and CCD detectors)

Photoreflectance investigation of InAs quantum dashes embedded in In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum well grown on InP substrate

W. Rudno-Rudziński, R. Kudrawiec, G. Sęk, J. Misiewicz, A. Somers, R. Schwertberger, J. P. Reithmaier, and A. Forchel

Appl. Phys. Lett. 88, 141915 (2006); http://dx.doi.org/10.1063/1.2187496 (3 pages) | Cited 10 times

Online Publication Date: 5 April 2006

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Photoreflectance (PR) measurements were performed on molecular-beam-epitaxy-grown self-assembled InAs quantum dashes (QDashes) embedded in an In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum well grown on InP substrate. PR resonances related to optical transitions in all relevant parts of the structure, i.e., InAs/In0.53Ga0.47As QDashes, InAs/In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum well, and in In0.53Ga0.23Al0.24As barriers were observed. By matching the theoretical calculations performed within the effective mass approximation with experimental data, the energy level structure of the whole system was determined. On the basis of the obtained energy level diagram, it was concluded that both electrons and heavy holes are localized within the InAs/In0.53Ga0.47As QDashes, the structure is of Type I.
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78.67.Lt Quantum wires
73.21.Fg Quantum wells
78.67.De Quantum wells
78.20.-e Optical properties of bulk materials and thin films
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Antisite defect-free Lu3(GaxAl1−x)5O12:Pr scintillator

M. Nikl, J. Pejchal, E. Mihokova, J. A. Mares, H. Ogino, A. Yoshikawa, T. Fukuda, A. Vedda, and C. D’Ambrosio

Appl. Phys. Lett. 88, 141916 (2006); http://dx.doi.org/10.1063/1.2191741 (3 pages) | Cited 24 times

Online Publication Date: 5 April 2006

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Pr-doped Lu3(GaxAl1−x)5O12:Pr, x = 0–1, single crystals were grown by the micro-pulling-down method. We study luminescence and scintillation characteristics of the sample set focusing on their dependence on the gallium content. For x = 0.4 we obtain the high figure-of-merit material with elevated density, high efficiency, and very fast scintillation response below 20 ns without any slower components. Improvement of scintillation performance is explained as due to the absence of the antisite LuAl defects that was for the first time realized in such bulk garnet single crystals grown from the high temperature melt.
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78.60.Kn Thermoluminescence
78.55.Hx Other solid inorganic materials

Correlation between optical properties and interface morphology of GaAs/AlGaAs quantum wells

N. Moret, D. Y. Oberli, E. Pelucchi, N. Gogneau, A. Rudra, and E. Kapon

Appl. Phys. Lett. 88, 141917 (2006); http://dx.doi.org/10.1063/1.2193039 (3 pages) | Cited 8 times

Online Publication Date: 5 April 2006

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We investigate the embedded interfaces of GaAs/AlGaAs quantum wells grown by metal organic vapor phase epitaxy on slightly (<1°)-misoriented (001) substrates using selective etching and atomic force microscopy. Depending on the substrate misorientation, we observe different growth modes at the embedded interfaces, which are directly correlated to the photoluminescence linewidth. We show that the narrowest linewidth is obtained on 0.2°-off (001) substrates for which the heterointerfaces consist of atomically smooth narrow terraces.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
68.65.Fg Quantum wells
68.35.Ct Interface structure and roughness

Electroluminescence at 375 nm from a ZnO/GaN:Mg/c-Al2O3 heterojunction light emitting diode

D. J. Rogers, F. Hosseini Teherani, A. Yasan, K. Minder, P. Kung, and M. Razeghi

Appl. Phys. Lett. 88, 141918 (2006); http://dx.doi.org/10.1063/1.2195009 (3 pages) | Cited 77 times

Online Publication Date: 6 April 2006

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n-ZnO/p-GaN:Mg heterojunction light emitting diode (LED) mesas were fabricated on c-Al2O3 substrates using pulsed laser deposition for the ZnO and metal organic chemical vapor deposition for the GaN:Mg. High crystal quality and good surface morphology were confirmed by x-ray diffraction and scanning electron microscopy. Room temperature (RT) photoluminescence (PL) showed an intense main peak at 375 nm and a negligibly low green emission indicative of a near band edge excitonic emission from a ZnO layer with low dislocation/defect density. The LEDs showed I-V characteristics confirming a rectifying diode behavior and a RT electroluminescence (EL) peaked at about 375 nm. A good correlation between the wavelength maxima for the EL and PL suggests that recombination occurs in the ZnO layer and that it may be excitonic in origin. This also indicates that there is significant hole injection from the GaN:Mg into the ZnO.
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85.60.Jb Light-emitting devices

Observation of donor-acceptor pair spectra in the photoluminescence of H- and Zn-implanted ZnO single crystals

D. C. Reynolds, C. W. Litton, T. C. Collins, J. E. Hoelscher, and J. Nause

Appl. Phys. Lett. 88, 141919 (2006); http://dx.doi.org/10.1063/1.2188046 (3 pages) | Cited 2 times

Online Publication Date: 6 April 2006

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Donor-acceptor (D-A) pair spectra have been observed in the photoluminescence radiative recombination of selected donor bound exciton complexes in zinc oxide (ZnO) single crystals that have been ion implantation doped with H and Zn atoms and subsequently annealed in a nitrogen (N2) atmosphere at temperatures in the range of 700–800 °C. Observations of the D-A pair spectra are explained as the bound states of Hopfield’s bound exciton complex model, in terms of the effective mass approximation of the wurtzitic ZnO energy band structure.
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81.05.Dz II-VI semiconductors
71.55.Gs II-VI semiconductors
78.55.Et II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
71.20.Nr Semiconductor compounds
71.35.-y Excitons and related phenomena

Grain-boundary resistivity versus grain size distribution in three-dimensional polycrystals

G. Dezanneau, A. Morata, A. Tarancón, M. Salleras, F. Peiró, and J. R. Morante

Appl. Phys. Lett. 88, 141920 (2006); http://dx.doi.org/10.1063/1.2189017 (3 pages) | Cited 2 times

Online Publication Date: 6 April 2006

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We have studied the accuracy of the bricklayer model in the evaluation of the grain-boundary resistivity associated to a real three-dimensional (3D) polycrystal. An impedance network electrically equivalent to the 3D structure has been solved by direct calculation. In order to examine the progressive evolution from the bricklayer model to a completely disordered system, the ideal polycrystal was modified in a controlled way, according to a Voronoï diagram approach. From this, the grain-boundary resistivity of a polycrystal, as deduced from the 3D bricklayer model, is lower than the real value. The upper limit of the error made is around 15% in relation to the real one.
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61.72.Mm Grain and twin boundaries

Size-dependent thermal conductivity of zinc oxide nanobelts

Ambarish J. Kulkarni and Min Zhou

Appl. Phys. Lett. 88, 141921 (2006); http://dx.doi.org/10.1063/1.2193794 (3 pages) | Cited 33 times

Online Publication Date: 6 April 2006

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The thermal conductivity of [01math0]-oriented ZnO nanobelts 19–41 Å in size is characterized over the temperature range of 500–1500 K using the Green-Kubo approach. Values obtained are one order of magnitude lower than that for bulk ZnO single crystal. Surface scattering of phonons and the high surface-to-volume ratios of the nanobelts are primarily responsible for the significantly lower values and the size dependence observed. The conductivity is also found to decrease with temperature and this decrease is attributed to thermal softening of the material, three- and four-phonon processes, and optical phonon interactions.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
63.20.K- Phonon interactions
72.10.Di Scattering by phonons, magnons, and other nonlocalized excitations

Effect of hydrogen on the growth of thin hydrogenated amorphous carbon films from thermal energy radicals

E. Neyts, A. Bogaerts, and M. C. M. van de Sanden

Appl. Phys. Lett. 88, 141922 (2006); http://dx.doi.org/10.1063/1.2193803 (3 pages) | Cited 17 times

Online Publication Date: 6 April 2006

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Molecular dynamics simulations have been performed to investigate the growth of thin hydrogenated amorphous carbon (a-C:H) films from radical species with thermal energy. It is found that the incorporation of H into the film increases the mass density. The maximum mass density is reached for a H flux of about 10%. The atom density of the films reaches a maximum at a H flux of about 30%. It is shown that these effects are a result of the change in microstructure of the films, including a H-induced sp to sp2 to sp3 shift. These results are important for thin a-C:H film deposition techniques where chemisorption of radical species is the main growth mechanism.
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68.55.A- Nucleation and growth
68.43.Mn Adsorption kinetics
61.43.Er Other amorphous solids

Nitrogen-induced hindering of In incorporation in InGaAsN

S. Rubini, G. Bais, A. Cristofoli, M. Piccin, R. Duca, C. Nacci, S. Modesti, E. Carlino, F. Martelli, A. Franciosi, G. Bisognin, D. De Salvador, P. Schiavuta, M. Berti, and A. V. Drigo

Appl. Phys. Lett. 88, 141923 (2006); http://dx.doi.org/10.1063/1.2193988 (3 pages) | Cited 6 times

Online Publication Date: 6 April 2006

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We compare the In content of quaternary InxGa1−xAs1−yNy and ternary InxGa1−xAs layers grown by plasma-assisted molecular beam epitaxy in similar conditions. Indium incorporation is found to decrease monotonically with increasing nitrogen content. The magnitude of the reduction strongly depends on N concentration, reaching about 20% of the nominal In content for N concentrations of y = 0.044.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.Dq Plasma-based ion implantation and deposition
68.55.-a Thin film structure and morphology

Mechanisms of thermally induced dewetting of ultrathin silicon-on-insulator

P. Sutter, W. Ernst, Y. S. Choi, and E. Sutter

Appl. Phys. Lett. 88, 141924 (2006); http://dx.doi.org/10.1063/1.2186741 (3 pages) | Cited 11 times

Online Publication Date: 7 April 2006

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Annealing of ultrathin silicon-on-insulator drives the formation of pinholes in the Si template, which in turn triggers a dewetting of the monocrystalline Si slab that is strongly affected by its crystallographic structure. An initial phase of well-defined square openings in the Si is followed by a hierarchical sequence of more complex branched shapes of the dewetting front. Annealing temperatures of about 800 °C, near the onset of significant thermally activated mass transport, drive a slow and controlled evolution that allows us to identify the mechanism underlying the dewetting and explain the spontaneous formation of well-defined Si patterns at submicron dimensions.
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68.08.Bc Wetting
61.72.Cc Kinetics of defect formation and annealing

Nanoheteroepitaxial lateral overgrowth of GaN on nanoporous Si(111)

K. Y. Zang, Y. D. Wang, S. J. Chua, L. S. Wang, S. Tripathy, and C. V. Thompson

Appl. Phys. Lett. 88, 141925 (2006); http://dx.doi.org/10.1063/1.2189114 (3 pages) | Cited 10 times

Online Publication Date: 7 April 2006

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Nanoheteroepitaxial (NHE) lateral overgrowth of GaN on nanoporous Si(111) substrates has been demonstrated. Nanopore arrays in Si(111) surfaces were fabricated using anodized aluminum oxide templates as etch masks, resulting in an average pore diameter and depth of about 60 and 160–180 nm, respectively. NHE growth of AlN and GaN was found to result in a significant reduction in the threading dislocation density (<108 cm−2) compared to that on flat Si(111). Most dislocations that originate at the Si interface bent to lie in the GaN (0001) basal plane during lateral growth over the pore openings. E2 phonon blueshifts in the Raman spectra indicate a significant relaxation of the tensile stress in the coalesced GaN films, due to three-dimensional stress relaxation mechanisms on porous substrates. Our results show that a single step lateral overgrowth of GaN on nanopatterned Si(111) substrates without a dielectric mask is a simple way to improve the crystalline quality of GaN layers for microelectronic applications.
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81.05.Ea III-V semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
78.30.Fs III-V and II-VI semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.40.Jj Elasticity and anelasticity, stress-strain relations
63.20.-e Phonons in crystal lattices

Raman studies of Bi2CuO4 at high pressures

F. X. Zhang and S. K. Saxena

Appl. Phys. Lett. 88, 141926 (2006); http://dx.doi.org/10.1063/1.2189450 (3 pages) | Cited 2 times

Online Publication Date: 7 April 2006

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The tetragonal compound Bi2CuO4 was investigated at high pressures by using an in situ Raman scattering method. A pressure-induced structural transition started at 20 GPa and completed before 37.2 GPa was found. Raman measurements revealed that the above phase transition is reversible.
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64.70.K- Solid-solid transitions
62.50.-p High-pressure effects in solids and liquids
78.30.Hv Other nonmetallic inorganics
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Proposal for an electrical spin cell with single barrier

B. H. Wu and Kang-Hun Ahn

Appl. Phys. Lett. 88, 142101 (2006); http://dx.doi.org/10.1063/1.2182069 (3 pages)

Online Publication Date: 3 April 2006

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We propose a spin cell based on photon-assisted tunneling through a conventional semiconductor barrier. The Dresselhaus spin-orbit interaction is included to break the spin rotation symmetry. Due to the in-plane electric field induced asymmetric momentum distribution in one lead, continuous flows of spin currents are driven through a barrier by an ac field. The net charge current remains zero. The spin current via photon-assisted tunneling can be readily adjusted via tuning the ac frequency or the in-plane electric field. This device may function as an ideal spin cell to supply spin currents in the spintronics circuit.
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72.25.-b Spin polarized transport
73.40.Gk Tunneling
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Analysis of graphene nanoribbons as a channel material for field-effect transistors

B. Obradovic, R. Kotlyar, F. Heinz, P. Matagne, T. Rakshit, M. D. Giles, M. A. Stettler, and D. E. Nikonov

Appl. Phys. Lett. 88, 142102 (2006); http://dx.doi.org/10.1063/1.2191420 (3 pages) | Cited 103 times

Online Publication Date: 3 April 2006

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Electronic properties of graphene (carbon) nanoribbons are studied and compared to those of carbon nanotubes. The nanoribbons are found to have qualitatively similar electron band structure which depends on chirality but with a significantly narrower band gap. The low- and high-field mobilities of the nanoribbons are evaluated and found to be higher than those of carbon nanotubes for the same unit cell but lower at matched band gap or carrier concentration. Due to the inverse relationship between mobility and band gap, it is concluded that graphene nanoribbons operated as field-effect transistors must have band gaps <0.5 eV to achieve mobilities significantly higher than those of silicon and thus may be better suited for low power applications.
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85.30.Tv Field effect devices
71.20.Tx Fullerenes and related materials; intercalation compounds
73.22.-f Electronic structure of nanoscale materials and related systems

On-chip photoconductive excitation and detection of pulsed terahertz radiation at cryogenic temperatures

C. Wood, J. Cunningham, P. C. Upadhya, E. H. Linfield, I. C. Hunter, A. G. Davies, and M. Missous

Appl. Phys. Lett. 88, 142103 (2006); http://dx.doi.org/10.1063/1.2191423 (3 pages) | Cited 4 times

Online Publication Date: 3 April 2006

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We report on measurements of the excitation, propagation, and detection of picosecond duration electrical pulses at cryogenic ( ∼ 4 K) temperatures in a microstrip circuit. A reduction is observed in the measured excitation and propagating pulse widths at low temperatures, compared with room temperature. The results indicate both that the electrical properties of low-temperature-grown GaAs make it suitable for photoconductive excitation and detection in cryogenic optoelectric circuits and that an organic polymer is a good transmissive medium for terahertz (THZ) frequency range excitations at low temperatures. This work will prove an invaluable starting point for future guided wave terahertz experiments at cryogenic temperatures.
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85.60.-q Optoelectronic devices
84.40.Dc Microwave circuits
84.40.Az Waveguides, transmission lines, striplines

Defects in silicon nanowires

R. P. Wang

Appl. Phys. Lett. 88, 142104 (2006); http://dx.doi.org/10.1063/1.2191830 (3 pages) | Cited 7 times

Online Publication Date: 4 April 2006

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Defects in silicon nanowires have been investigated using the electron spin resonance (ESR) method. The ESR signals consist of three features: a strong resonance at g = 2.002 49, a weak line at g = 2.000 48, and a broad feature at g = 2.005 41. From the saturation behavior and oxidation-related and temperature dependence analysis, we ascribe that the strong resonance corresponds to the EX center and the weak line to the well-assigned E′ center. We argue that the assignment of the broad feature to Pb centers [ A. Baumer et al., Appl. Phys. Lett. 85, 943 (2004) ] is oversimplified, and its physical origins may include dangling bonds in amorphous silicon.
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81.05.Cy Elemental semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials
71.55.Cn Elemental semiconductors
76.30.-v Electron paramagnetic resonance and relaxation
81.65.Mq Oxidation

Highly strain-relaxed ultrathin SiGe-on-insulator structure by Ge condensation process combined with H+ irradiation and postannealing

Masanobu Miyao, Masanori Tanaka, Isao Tsunoda, Taizoh Sadoh, Toyotsugu Enokida, Hiroyasu Hagino, Masaharu Ninomiya, and Masahiko Nakamae

Appl. Phys. Lett. 88, 142105 (2006); http://dx.doi.org/10.1063/1.2192644 (3 pages) | Cited 10 times

Online Publication Date: 4 April 2006

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Strain-relaxation process of SiGe-on-insulator (SGOI) structures in the oxidation induced Ge condensation method has been investigated as a function of the SiGe thickness. Complete relaxation was obtained for thick SGOI layers (>100 nm). However, the relaxation rates abruptly decreased with decreasing SiGe thickness below 50 nm, i.e., the relaxation rate of 30% at 30 nm SiGe thickness. In order to improve this phenomenon, a method combined with H+ irradiation with a medium dose (5×1015 cm−2) and postannealing (1200 °C) has been developed. This successfully achieved the high relaxation rate (70%) in the ultrathin SGOI (30 nm).
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81.05.Hd Other semiconductors
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors

Quantitative mobility spectrum analysis of AlGaN/GaN heterostructures using variable-field hall measurements

N. Biyikli, J. Xie, Y.-T. Moon, F. Yun, C.-G. Stefanita, S. Bandyopadhyay, H. Morkoç, I. Vurgaftman, and J. R. Meyer

Appl. Phys. Lett. 88, 142106 (2006); http://dx.doi.org/10.1063/1.2195011 (3 pages) | Cited 8 times

Online Publication Date: 5 April 2006

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Carrier transport properties of AlGaN/GaN heterostructures have been analyzed with the quantitative mobility spectrum analysis (QMSA) technique. The nominally undoped Al0.08Ga0.92N/GaN sample was grown by plasma-assisted molecular beam epitaxy on a GaN/sapphire template prepared with hydride vapor phase epitaxy. Variable-magnetic-field Hall measurements were carried out in the temperature range of 5–300 K and magnetic field range of 0.01–7 T. QMSA was applied to the experimental variable-field data to extract the concentrations and mobilities associated with the high-mobility two-dimensional electron gas and the relatively low-mobility bulk electrons for the temperature range investigated. The mobilities at T = 80 K are found to be 7100 and 880 cm2/V s, respectively, while the corresponding carrier densities are 7.0×1011 and 8×1014 cm−3. Any conclusions drawn from conventional Hall measurements at a single magnetic field would have been highly misleading.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.My Galvanomagnetic and other magnetotransport effects

InGaAs dual channel transistors with negative differential resistance

Takeyoshi Sugaya, Kazuhiro Komori, Takashi Yamane, Souichirou Hori, and Kenji Yonei

Appl. Phys. Lett. 88, 142107 (2006); http://dx.doi.org/10.1063/1.2193728 (3 pages) | Cited 3 times

Online Publication Date: 5 April 2006

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We demonstrate InGaAs dual channel transistors (DCTs) with negative differential resistance (NDR) fabricated on an InP (001) substrate. The dual channel structure consists of high and low mobility InGaAs quantum wells combined with an InAlAs barrier layer. NDR characteristics of the DCTs depend on the thicknesses of the low mobility and barrier layers and the indium content of the high mobility channel. The NDR mechanism is thought to be the carrier transfer from the high mobility channel to the low mobility channel.
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85.30.Pq Bipolar transistors
73.21.Fg Quantum wells
73.63.Hs Quantum wells
72.20.Fr Low-field transport and mobility; piezoresistance

Fabrication of silicon-on-SiO2/diamondlike-carbon dual insulator using ion cutting and mitigation of self-heating effects

Zengfeng Di, Paul K. Chu, Ming Zhu, Ricky K. Y. Fu, Suhua Luo, Lin Shao, M. Nastasi, Peng Chen, T. L. Alford, J. W. Mayer, Miao Zhang, Weili Liu, Zhitang Song, and Chenglu Lin

Appl. Phys. Lett. 88, 142108 (2006); http://dx.doi.org/10.1063/1.2192981 (3 pages) | Cited 3 times

Online Publication Date: 5 April 2006

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A diamondlike-carbon (DLC) layer was used to substitute for the buried SiO2 layer in silicon on insulator (SOI) to mitigate the self-heating effects in our previous study. However, we discovered drawbacks associated with the inferior Si/DLC interface, inadequate thermal stability as well as carbon-silicon interdiffusion at the Si/DLC interface that could hamper future application of this silicon-on-diamond structure to microelectronic devices. In this work, we introduced a silicon dioxide barrier layer between the Si film and DLC buried layer to form a silicon-on-SiO2/DLC dual-insulator structure to tackle these problems. Cross-sectional high-resolution transmission electron microscopy reveals that the Si/insulator interface is atomically flat and the top Si layer has nearly perfect crystalline quality. The SiO2/DLC dual-insulator layer retains excellent insulating properties at typical complementary metal oxide silicon processing temperatures. Numerical simulation reveals that the negative differential resistance and channel temperature are significantly reduced compared with those of the same metal oxide semiconductor field effect transistors fabricated in conventional SiO2-based SOI, suggesting that the silicon-on-dual-insulator structure can alleviate the self-heating penalty effectively.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.60.Dv Thermal stability; thermal effects

Electrical properties of n-type GaPN grown by molecular-beam epitaxy

Yuzo Furukawa, Hiroo Yonezu, Akihiro Wakahara, Yusuke Yoshizumi, Yoshiro Morita, and Atsushi Sato

Appl. Phys. Lett. 88, 142109 (2006); http://dx.doi.org/10.1063/1.2193350 (3 pages) | Cited 4 times

Online Publication Date: 6 April 2006

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We have investigated electrical properties of n-GaPN layers grown by molecular-beam epitaxy with an rf-plasma source using sulfur and tellurium as dopants. The electron concentration in n-GaPN was about 10 times lower than that in n-GaP. Desorption of dopants from the grown surface by impinging N atoms may be one of the possible causes for the reduced electron concentration. In addition, electron mobilities in GaPN were restricted by ionized impurity scattering even at room temperature (RT). N atoms at N-related levels could trap the electrons, and these ionized N could act as a Columb scattering center for free electrons even at RT.
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73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
61.72.uj III-V and II-VI semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
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