jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

15 Jul 2005

Volume 98, Issue 2, Articles (02xxxx)

Page 2 of 6 Pages Previous Page Next Page | Jump to Page
back to top
RSS Feeds

Molecular-beam epitaxial growth and characteristics of highly uniform InAs/GaAs quantum dot layers

Zetian Mi and Pallab Bhattacharya

J. Appl. Phys. 98, 023510 (2005); http://dx.doi.org/10.1063/1.1985969 (5 pages) | Cited 17 times

Online Publication Date: 21 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated the molecular-beam epitaxial growth and structural and photoluminescence characteristics of self-organized InAs/GaAs quantum dot bilayers, in which a first seed layer of stressor dots is followed by a GaAs barrier layer and a second layer of active dots. At room temperature, the peak emission wavelength is at ∼ 1.4 μm. By optimizing the growth parameters for both dot layers and the GaAs barrier layer, we have measured photoluminescence linewidths of 10.6 and 17.5 meV at 20 and 300 K, respectively. The measurement and analysis of temperature-dependent photoluminescence data indicate that there is no observable carrier redistribution amongst the dots with an increase of temperature and there is a high degree of size uniformity. The photoluminescence linewidth of 17.5 meV at 300 K is almost identical to that measured in the emission from a single dot, indicating that the linewidth is determined by homogeneous broadening.
Show PACS
81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Zn-doped GaSb epitaxial film absorption coefficients at terahertz frequencies and detector applications

Z. G. Hu, A. G. U. Perera, Y. Paltiel, A. Raizman, and A. Sher

J. Appl. Phys. 98, 023511 (2005); http://dx.doi.org/10.1063/1.1977195 (5 pages) | Cited 7 times

Online Publication Date: 21 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The reflectance measurements of p-type GaSb:Zn epitaxial films with different hole concentrations, grown by metalorganic vapor-phase epitaxy, have been investigated in the 3–30-THz frequency region. The experimental spectra were fitted using a classical harmonic Lorentz oscillator and the Drude model, illustrating that the hole effective mass and the mobility change with the carrier concentration. The hole effective mass was found to vary from 0.22m0 to 0.41m0 as the carrier concentration changed from 3.5×1017 to 3.8×1018 cm−3. The mobility values derived from the reflectance measurements were slightly smaller than the values obtained from Hall-effect measurements. A sublinear relationship between the absorption coefficient and the hole concentration was found at a frequency of 3 THz. Those results can be used for designing GaSb-based terahertz detectors.
Show PACS
78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
72.30.+q High-frequency effects; plasma effects
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Fr Low-field transport and mobility; piezoresistance

Investigation of the poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene]∕indium tin oxide interface using photoemission spectroscopy

B. Lägel, M. M. Beerbom, B. V. Doran, M. Lägel, A. Cascio, and R. Schlaf

J. Appl. Phys. 98, 023512 (2005); http://dx.doi.org/10.1063/1.1949276 (7 pages) | Cited 6 times

Online Publication Date: 22 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The interface between the luminescent polymer poly [2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and sputter-cleaned indium tin oxide (ITO) was investigated using photoemission spectroscopy in combination with in situ thin film deposition. MEH-PPV was deposited in high vacuum directly from toluene solution on the ITO substrate using a home-built electrospray thin-film deposition system. The deposition was carried out in multiple steps without breaking the vacuum. In between deposition steps the sample was characterized with x-ray and ultraviolet photoemission spectroscopy. The evaluation of the spectra sequence allowed the determination of the orbital lineup (charge injection barriers) at the interface, as well as the MEH-PPV growth mode at the interface.
Show PACS
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
71.20.Rv Polymers and organic compounds
71.20.Nr Semiconductor compounds
68.55.A- Nucleation and growth
81.15.Pq Electrodeposition, electroplating
79.60.Fr Polymers; organic compounds
79.60.Jv Interfaces; heterostructures; nanostructures
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.30.+y Surface double layers, Schottky barriers, and work functions

Investigation of composition fluctuations in GaN:Mg using optical transmission spectroscopy, near-field scanning optical microscopy, and scanning Kelvin probe microscopy

B. Han, B. W. Wessels, and M. P. Ulmer

J. Appl. Phys. 98, 023513 (2005); http://dx.doi.org/10.1063/1.1948527 (6 pages) | Cited 6 times

Online Publication Date: 22 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Composition fluctuations in GaN:Mg have been investigated by optical transmission spectroscopy, near-field scanning optical microscopy (NSOM), and scanning Kelvin probe microscopy (SKPM). An Urbach tail is observed in the optical transmission spectrum of heavily Mg-doped GaN, with the magnitude of Urbach energy increasing with increasing compositional/potential fluctuations. From the relationship between the Urbach energy and the potential fluctuation magnitude, the spatial size of the compositional fluctuations in GaN:Mg (with the average Mg concentration of ∼ 4×1019 cm−3) is calculated to be 220 nm. The nanoscale compositional fluctuations are determined by NSOM and SKPM. A spatial variation of the transmission mode NSOM intensity is observed with a characteristic wavelength of ∼ 300 nm, which is attributed to the inhomogeneous distribution of Mg. The normalized root-mean-square (rms) fluctuation of the transmission mode NSOM intensity for heavily Mg-doped GaN is a factor of 5 greater than that for undoped GaN. Similar microstructure patterns are observed in the NSOM and surface potential images of GaN:Mg as probed by SKPM. The variation of local surface potential (on the order of 100 mV) is attributed to the same compositional fluctuations of Mg, which changes the local surface work function. The local Mg concentrations are calculated from the SKPM image. For GaN:Mg with the Mg concentration of 4×1019 cm−3, a rms value of 5.4×1019 cm−3 of the compositional fluctuations has been observed.
Show PACS
61.72.S- Impurities in crystals
78.40.Fy Semiconductors
73.30.+y Surface double layers, Schottky barriers, and work functions
68.37.Uv Near-field scanning microscopy and spectroscopy

Growth stresses and cracking in GaN films on (111) Si grown by metal-organic chemical-vapor deposition. I. AlN buffer layers

Srinivasan Raghavan and Joan M. Redwing

J. Appl. Phys. 98, 023514 (2005); http://dx.doi.org/10.1063/1.1978991 (9 pages) | Cited 23 times

Online Publication Date: 22 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Intrinsic stress evolution during the growth of GaN by metal-organic chemical-vapor deposition on (111) Si, using an AlN buffer layer, was monitored in situ with a multiple-beam optical stress sensor. Data show that stress evolution takes place in two stages: an initial compressive regime up to about 100 nm in thickness followed by a transition to a constant tensile stress, ∼ 0.3 GPa, in films up to 1 μm thick. Correlation of the stress evolution with surface morphological evolution by sequential atomic force microscopy images clearly shows that the incremental stress remains compressive in spite of grain coalescence, which is generally considered to be the dominant source of tensile stress in GaN films on sapphire. Rather, the most dominant feature accompanying the transition in stress from compressive to tensile, which takes place after grain coalescence, is an increase in the lateral size of individual islands. It is shown that this incremental tensile stress accompanied by an increase in lateral grain size can be accounted for by the annihilation of free volume associated with the grain boundaries. On samples cooled to room temperature, surface cracks mainly on the (1010) planes are observed to have channeled in films thicker than 250 nm. Analysis of cracking using the theory of brittle fracture, using the measured growth stress profile and value for the critical thickness, yields a thermal-expansion mismatch stress off 1.1 GPa for GaN films deposited at 1100 °C and cooled to room temperature.
Show PACS
81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.60.Bs Mechanical and acoustical properties
68.35.Gy Mechanical properties; surface strains
68.37.Ps Atomic force microscopy (AFM)
68.55.-a Thin film structure and morphology
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.72.Mm Grain and twin boundaries
65.40.De Thermal expansion; thermomechanical effects

Growth stresses and cracking in GaN films on (111) Si grown by metalorganic chemical vapor deposition. II. Graded AlGaN buffer layers

Srinivasan Raghavan and Joan Redwing

J. Appl. Phys. 98, 023515 (2005); http://dx.doi.org/10.1063/1.1978992 (8 pages) | Cited 15 times

Online Publication Date: 22 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Growth stress and critical thickness for cracking on cooling in GaN films deposited by metalorganic chemical vapor deposition on (111) Si using graded AlGaN (from AlN to GaN) buffer layers, 0.1–2 μm thick, were examined. During the growth of the graded buffer layers, the incremental growth stress was observed to change from tension ( ∼ +1 to +1.5 GPa) to compression ( ∼ −1 to −1.7 GPa). An interruption in the composition grading during the compressive segment, followed by continued growth of the AlGaN composition at the interruption, resulted in the eventual transition to a tensile stress in films as thick as 0.75 μm. A similar stress evolution, a reduction in the value of the initial compressive stress with thickness, was observed during the growth of 1‐μm-thick GaN layers on 2‐μm-thick graded AlGaN buffer layers. Such stress evolution, at thickness far beyond coalescence, cannot be explained by initial grain coalescence stresses alone. A combination of compressive stress generation due to the change in AlGaN composition and tensile stress generation due to the lateral increase in grain size with thickness are used to explain these results. In the GaN layer, the thickness at which the compressive-to-tensile stress transition takes place increases and the magnitude of the final stress decreases with an increase in the thickness of the graded AlGaN buffer layer. X-ray diffraction results show that this is due to increasing accommodation of the tensile stress generating microstructural changes within the thickness of the AlGaN buffer layer, thus reducing the level of tensile stress in the subsequent GaN layer. A 1‐μm-thick graded AlGaN buffer layer enabled the growth of a 1‐μm-thick GaN layer that is crack-free after dicing at room temperature.
Show PACS
81.05.Ea III-V semiconductors
68.60.Bs Mechanical and acoustical properties
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Electrochemically controlled transport of lithium through ultrathin SiO2

Nava Ariel, Gerbrand Ceder, Donald R. Sadoway, and Eugene A. Fitzgerald

J. Appl. Phys. 98, 023516 (2005); http://dx.doi.org/10.1063/1.1989431 (7 pages) | Cited 7 times

Online Publication Date: 26 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Monolithically integrating the energy supply unit on a silicon integrated circuit (IC) requires the development of a thin-film solid-state battery compatible with silicon IC fabrication methods, materials, and performance. We have envisioned materials that can be processed in a silicon fabrication environment, thus bringing local stored energy to silicon ICs. By incorporating the material directly onto the silicon wafer, the economic parallelism that silicon complementary metal-oxide-semiconductor (CMOS) technology has enjoyed can be brought to power incorporation in each IC on a processed wafer. It is natural to look first towards silicon CMOS materials, and ask which materials need enhancement, which need replacement, and which can be used “as is.” In this study, we begin by using two existing CMOS materials and one unconventional material for the construction of a source of electric power. We have explored the use of thermally grown silicon dioxide (SiO2) as thin as 9 nm acting as an electrolyte material candidate in a solid-state power cell integrated on silicon. Other components of the thin-film cell consisted of rf-sputtered lithium cobalt oxide (LiCoO2) as the cathode and highly doped n-type polycrystalline silicon (polysilicon) grown by low-pressure chemical-vapor deposition as the anode. All structures were fabricated using conventional microelectronics fabrication technology. The charge and discharge behaviors of the LiCoO2/SiO2/polysilicon cells were studied. On the basis of the impedance measurements an equivalent circuit model of an ultrathin cell was inferred, and its microstructure was characterized by electron microscopy imaging. In spite of its high series resistance ( ∼ 4×107 Ω), we have shown that an ultrathin layer of an as-deposited Li-free SiO2 is an interesting candidate for an electrolyte or controllable barrier layer in lithium-ion-based devices.
Show PACS
85.30.Tv Field effect devices
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
82.47.Aa Lithium-ion batteries

Nitrogen effects on generation and velocity of dislocations in Czochralski-grown silicon

I. Yonenaga

J. Appl. Phys. 98, 023517 (2005); http://dx.doi.org/10.1063/1.1990259 (6 pages) | Cited 9 times

Online Publication Date: 26 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The dynamic properties of individual dislocations in nitrogen (N)-doped Czochralski-grown Si crystals with concentrations up to 6×1015 cm−3 were investigated at temperatures of 650–950 °C using the etch pit technique and compared with such characteristics of N-free Si crystals. The velocity of dislocations in motion in N-doped crystals was revealed to be unaffected by N doping. It was found that the generation of dislocations from a surface scratch was suppressed in N-doped Si and that the critical stress for dislocation generation increased with N concentration, which is interpreted as being due to dislocation immobilization caused by impurity segregation. N doping is concluded to be effective in the promotion of precipitation of oxygen impurity resulting in immobilization of dislocations.
Show PACS
66.30.Lw Diffusion of other defects
61.72.Yx Interaction between different crystal defects; gettering effect
81.05.Cy Elemental semiconductors
61.72.uf Ge and Si
61.72.S- Impurities in crystals
62.20.-x Mechanical properties of solids
64.75.-g Phase equilibria

Convex-shaped decay curve of carriers in a vertically coupled InAs/GaAs quantum dot

J. S. Yim, Y. D. Jang, D. Lee, H. G. Lee, and S. K. Noh

J. Appl. Phys. 98, 023518 (2005); http://dx.doi.org/10.1063/1.1994940 (4 pages) | Cited 3 times

Online Publication Date: 26 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In a study using time-resolved photoluminescence (PL) to examine the carrier dynamics of a vertically coupled InAs/GaAs quantum dot (QD) of 20 periods, we observed an initial slow carrier decay followed by a fast decay. The time at which the transition from slow to fast decay occurred increased on going to lower QD states at a fixed excitation power, and increased with increasing excitation intensity at a fixed QD state. This behavior is attributed to the relatively efficient vertical transfer of carriers in the vertically coupled InAs/GaAs QD. In addition, this vertical carrier transfer makes the rise of the PL signal slower at lower-energy states. This peculiar carrier dynamics behavior was not observed in a single-layered QD or in a vertically uncoupled QD of 20 periods.
Show PACS
73.63.Kv Quantum dots
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.21.La Quantum dots

Molecular modeling of water diffusion in amorphous SiC

Haiying He, Mrinalini Deshpande, Richard E. Brown, Ravindra Pandey, and Udo C. Pernisz

J. Appl. Phys. 98, 023519 (2005); http://dx.doi.org/10.1063/1.1968439 (5 pages) | Cited 1 time

Online Publication Date: 28 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The diffusion of water in amorphous SiC (a-SiC) was investigated by molecular modeling methods based on density functional theory. It was assumed that the structure of a-SiC at the molecular level can be described by a model that takes into account a distribution of cage structures which consist of SiC units forming n-member rings from a suitable precursor in a chemical vapor deposition process. Electronic structure calculations are then performed to determine the energy barrier that the water molecule encounters when it penetrates through SiC rings of various sizes. It has been found that along its diffusion path through the SiC network the water molecule neither breaks up nor attaches itself to the SiC network and the energy barrier for diffusion depends mainly on the local SiC ring topology.
Show PACS
66.30.-h Diffusion in solids
61.43.Dq Amorphous semiconductors, metals, and alloys

Acoustic emission and nonergodic states of the electric-field-induced-phase transition of PbMg1/3Nb2/3O3

E. Dul’kin, M. Roth, B. Dkhil, and J. M. Kiat

J. Appl. Phys. 98, 023520 (2005); http://dx.doi.org/10.1063/1.1980527 (4 pages) | Cited 8 times

Online Publication Date: 29 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Acoustic emission (AE) method was used to investigate the electric-field-induced-phase transition in the well-known relaxor Pb(Mg1/3Nb2/3)O3 (PMN). We show that in the field cooling process the induced-phase transition is accompanied by an AE signal, which reflects relaxation of the strong stress, associated with arising of a macroscopic domains structure similar to martensitic phase transition. However, using a procedure in which the field is applied after a zero field cooling, no AE signal is detected even after a very long time higher than expected for the appearance of the induced-phase transition. The comparison with previous x-ray-diffraction results allowed to get in the last case interesting insights on the local and long-range polar order of the induced ferroelectric state because of absence of the relaxation of the strong stress due to percolation mechanism of this phase transition.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
62.65.+k Acoustical properties of solids
77.80.Dj Domain structure; hysteresis
77.80.B- Phase transitions and Curie point
64.70.K- Solid-solid transitions
81.30.Kf Martensitic transformations
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Unfaulting of dislocation loops in the GaInNAs alloy: An estimation of the stacking fault energy

M. Herrera, D. González, J. G. Lozano, R. García, M. Hopkinson, H. Y. Liu, M. Gutierrez, and P. Navaretti

J. Appl. Phys. 98, 023521 (2005); http://dx.doi.org/10.1063/1.1988976 (7 pages) | Cited 4 times

Online Publication Date: 29 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A study by transmission electron microscopy of the influence of the In and N contents in the ranges of 20%–35% and 1.1%–3%, respectively, on the microstructure of Ga1−xInxNyAs1−y quantum wells is presented. Frank dislocation loops characterized as extrinsic have been found in the samples with x ≥ 0.25. In these structures, threading dislocations appear as a consequence of the unfaulting of the loops for y ≥ 0.014. An analysis of the density and size of the dislocation loops has provided an estimation of the critical radius for the unfaulting process. A model for this critical radius of the unfaulting process of extrinsic Frank loops is proposed. From this model and experimental values of critical radius, an estimation of the stacking fault energy of the GaInNAs alloy has been made. We have found a reduction in the stacking fault energy of the GaInNAs alloys when increasing the N content from 1.4% to 2.3% in good agreement with the theoretical estimation of the stacking fault energies of zinc-blende GaN and InN.
Show PACS
81.07.St Quantum wells
81.05.Ea III-V semiconductors
68.65.Fg Quantum wells
61.72.Lk Linear defects: dislocations, disclinations
61.72.Nn Stacking faults and other planar or extended defects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

High nitrogen incorporation in GaAsN epilayers grown by chemical beam epitaxy using radio-frequency plasma source

M.-A. Pinault, A. Freundlich, J. A. H. Coaquira, and A. Fotkatzikis

J. Appl. Phys. 98, 023522 (2005); http://dx.doi.org/10.1063/1.1996853 (4 pages) | Cited 6 times

Online Publication Date: 1 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Nitrogen incorporation in GaAsN epilayers grown by chemical beam epitaxy using a radio-frequency (rf) plasma source as nitrogen precursor was studied as a function of growth conditions. For higher growth temperatures ( ∼ 460 °C), only higher rf power values yield significant incorporation of nitrogen. The nitrogen incorporation exhibits two behaviors with the growth rate: metal-organic-chemical-vapor-deposition and molecular-beam-epitaxy like behaviors at low and high growth rate, respectively. The highest nitrogen compositions are obtained at rates of about 1 μm/h. Despite a significant reduction of the N incorporation with increasing growth temperature, the optimization of the growth conditions allowed us to reach nitrogen concentrations up to 7.1% for samples fabricated at 460 °C. Films with higher nitrogen content exhibit low-temperature luminescence at energies higher than those predicted using the band-anticrossing model and an extrapolation of the literature data for smaller N composition.
Show PACS
81.05.Ea 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
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.55.A- Nucleation and growth

Controlling fluorescence lifetime of rare-earth element in amorphous inorganic solids via very small compositional adjustments

Yong Gyu Choi, Richard J. Curry, Bong Je Park, Kyong Hon Kim, Jong Heo, and Dan W. Hewak

J. Appl. Phys. 98, 023523 (2005); http://dx.doi.org/10.1063/1.1996854 (6 pages) | Cited 8 times

Online Publication Date: 1 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Fluorescence lifetime of hypersensitive 4f-4f transitions of rare-earth elements embedded in amorphous inorganic solids can be dramatically modified by compositional adjustment of the hosts tantamount to not more than 1 mol % without any elaborated thermal treatments. It is possible to modify a spontaneous emission rate of Dy3+:(math,math)→math transition in chalcogenide Ge–As–S glasses through selective addition of low levels of Ga and CsBr. Along with the change of the spontaneous emission rate, multiphonon relaxation rate involved in the (math,math) state also significantly varies upon the minute compositional adjustment. The combination of these effects results in the measured lifetime of the fluorescing (math,math) level being greatly enhanced. Such behaviors are attributed to the hypersensitive nature associated with the math↔math transition and preferential coordination of bromine in the nearest-neighboring shell of the Dy3+ ions, which is formed spontaneously during the vitrification process of the host materials. These experimental observations show the most extreme dependence of the fluorescence lifetime on small compositional changes reported compared to any other noncrystalline solid-state dielectric. As such coutilization of many hypersensitive transitions of rare-earth elements and those host materials used in this study may present a unique opportunity to control absorption and emission properties, especially fluorescence lifetimes, through a minute compositional adjustment.
Show PACS
63.20.K- Phonon interactions
78.55.Qr Amorphous materials; glasses and other disordered solids

Simple cubic three-dimensional photonic crystals based on macroporous silicon and anisotropic posttreatment

Sven Matthias, Frank Müller, and Ulrich Gösele

J. Appl. Phys. 98, 023524 (2005); http://dx.doi.org/10.1063/1.1993752 (4 pages) | Cited 16 times

Online Publication Date: 1 August 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Three-dimensional structures for photonic crystal applications have been fabricated up to now either by pure bottom-up approaches such as colloidal self-assembly, by pure top-down approaches using very large scale integration technology, or by interference lithography. Here we evaluate a concept enabling large photonic band gaps in simple cubic structures, the manufacturing of which is based on photoelectrochemical etching of strongly modulated macroporous silicon. A subsequent anisotropic etching of the porous structure, which exploits the crystallographic nature of the substrate used, converts the former circular cross section of the pores into a squared one. We theoretically study the dispersion behavior of photonic crystals being fabricated by this developed technique. The band-structure calculations are compiled with respect to the relative pore arrangement and the dielectric volume fraction. We present experimentally realized structures and characterize the photonic crystal optically. The reflectance measurements are in good agreement with corresponding band-structure calculations. Moreover, the introduced process extends the variety of designing and sculpturing three-dimensional microstructures to meet the requirements of a multitude of micro- and nanotechnological applications.
Show PACS
42.70.Qs Photonic bandgap materials
81.05.Rm Porous materials; granular materials
81.05.Cy Elemental semiconductors
61.43.Gt Powders, porous materials
81.65.Cf Surface cleaning, etching, patterning
back to top
RSS Feeds

Fluorine-doping concentration and fictive temperature dependence of self-trapped holes in SiO2 glasses

R. P. Wang, N. Tai, K. Saito, and A. J. Ikushima

J. Appl. Phys. 98, 023701 (2005); http://dx.doi.org/10.1063/1.1980536 (3 pages)

Online Publication Date: 18 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Fictive temperature (Tf) and fluorine (F)-doping concentration dependences of self-trapped holes (STHs) in silica glasses created by UV irradiation at low temperatures have been studied by the electron-paramagnetic-resonance method. It was found that the yield of STH decreases with decreasing Tf and increasing F-doping concentration. In combination with infrared spectra measurements, the correlation among Tf, F-doping concentration, Si–O bond length, and Si–O–Si bond angle was elucidated. We conclude that the change in both Tf and F doping can modify the network of SiO2 glass, leading to the suppression of the formation of STHs.
Show PACS
61.72.S- Impurities in crystals
71.55.Ht Other nonmetals
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.35.+c Brillouin and Rayleigh scattering; other light scattering
76.30.-v Electron paramagnetic resonance and relaxation

Effect of thermal annealing on the interband transitions and activation energies of CdTe/ZnTe quantum dots

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

J. Appl. Phys. 98, 023702 (2005); http://dx.doi.org/10.1063/1.1968440 (4 pages) | Cited 1 time

Online Publication Date: 19 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of rapid thermal annealing on CdTe/ZnTe quantum dots (QDs) was analyzed to investigate the interband transitions and the electron activation energy. The full width at half maximum of the photoluminescence (PL) peak corresponding to the interband transitions from the ground electronic subband to the ground heavy-hole band (E1‐HH1) in the CdTe/ZnTe QDs annealed at 330 °C decreased, and their integrated PL intensity of the E1‐HH1 transition peak significantly increased. The activation energy of electrons confined in CdTe/ZnTe QDs annealed at 330 °C increased as high as 77 meV, which was the highest value among the as-grown and annealed samples. These results indicate that the crystallinity of the CdTe/ZnTe QDs is improved by annealing, and the present results can help improve the understanding of the thermal annealing effect on the optical properties of CdTe/ZnTe QDs.
Show PACS
61.72.Cc Kinetics of defect formation and annealing
73.21.La Quantum dots
78.55.Et II-VI semiconductors
78.67.Hc Quantum dots

Thermally activated carrier transfer processes in InGaN/GaN multi-quantum-well light-emitting devices

C. L. Yang, L. Ding, J. N. Wang, K. K. Fung, W. K. Ge, H. Liang, L. S. Yu, Y. D. Qi, D. L. Wang, Z. D. Lu, and K. M. Lau

J. Appl. Phys. 98, 023703 (2005); http://dx.doi.org/10.1063/1.1978967 (5 pages) | Cited 7 times

Online Publication Date: 19 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have studied the temperature-dependent carrier transfer processes in InGaN/GaN multi-quantum-well light-emitting devices using various optical techniques such as photoluminescence, electroluminescence, and photoluminescence excitation spectra. The role of the defects in the GaN barrier neighboring to the InGaN region was demonstrated clearly in capturing carriers only at low temperatures. The physical origin of the defects was most possibly attributed to the stacking faults at the interface according to the high-resolution transmission electron spectroscopy pictures.
Show PACS
85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Charge trap levels in sulfur-doped chemical-vapor-deposited diamond with applications to ultraviolet dosimetry

E. Trajkov, S. Prawer, J. E. Butler, and S. M. Hearne

J. Appl. Phys. 98, 023704 (2005); http://dx.doi.org/10.1063/1.1984079 (7 pages) | Cited 4 times

Online Publication Date: 19 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Electrically active defects and traps in sulfur-doped polycrystalline diamond films synthesized by microwave-assisted chemical-vapor deposition are evaluated using thermally stimulated conductivity measurements after ultraviolet (UV) illumination. The measurements are found to be consistent with the latest theoretical predictions for the role of sulfur dopants in diamond. The suitability of S-doped diamond as a UV dosimeter is discussed.
Show PACS
81.05.Cy Elemental semiconductors
71.55.Cn Elemental semiconductors
71.20.Mq Elemental semiconductors
73.61.Cw Elemental semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Electronic structure of silicon quantum dots: Calculations of energy-gap redshifts due to oxidation

Masahiko Nishida

J. Appl. Phys. 98, 023705 (2005); http://dx.doi.org/10.1063/1.1985978 (6 pages) | Cited 9 times

Online Publication Date: 20 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Electronic state calculations are performed self-consistently using the extended Hückel-type nonorthogonal tight-binding method for two different oxygen configurations (backbonded and double-bonded oxygen configurations) on the H-covered surface of spherical Si35H36, Si47H60, Si71H84, Si136H120, Si148H120, and Si172H120 quantum dots. The size dependence of the effect of oxygen on the electronic structure of the Si dots is studied. Energy gaps calculated for both oxygen configurations can explain oxidation-induced redshifts in photoluminescence (PL) observed in porous Si. However, the energy gaps calculated for the backbonded oxygen model are around 2.2 eV and dipole allowed in all Si dots studied, whereas those for the double-bonded oxygen model are gradually decreased with the increase in size (2.3–1.7 eV), and optical transitions are dipole forbidden in the Si dots near 1 nm across and dipole allowed in the ones near 2 nm in diameter. The results calculated for the backbonded oxygen model coincide well with the experimental fact that the PL-peak energies are fixed at ∼ 2.1 eV when porous Si is exposed to air.
Show PACS
71.20.Mq Elemental semiconductors
78.55.Ap Elemental semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
73.21.La Quantum dots
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Electrical transport properties of aluminum-implanted 4H–SiC

J. Pernot, S. Contreras, and J. Camassel

J. Appl. Phys. 98, 023706 (2005); http://dx.doi.org/10.1063/1.1978987 (9 pages) | Cited 13 times

Online Publication Date: 20 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The free hole density and low-field mobility of aluminum-doped 4H–SiC were investigated in the temperature range of 100–900 K, both, experimentally and theoretically. Experimental data for implanted p-type 4H–SiC were compared with theoretical calculations using parameters determined for high-quality epitaxial layers. The deformation potential for intra- and intervalley scattering by acoustic phonons and the effective coupling constant for intra- and intervalley scattering by nonpolar optical phonons were determined. The detailed analysis of the implanted layers with aluminum-targeted concentration ranging from 3.33×1018 to 1021 cm−3 shows that (i) about half of the implanted atoms are electrically active in the SiC lattice, (ii) a systematic compensation of about 10% of the doping level is induced by the implantation process, (iii) two different ionization energies for the aluminum atoms have to be used. Their origin is discussed in terms of inequivalent hexagonal and cubic lattice sites. Finally, the doping dependence of the ionization ratio and Hall mobility are given for non- and weakly (10%) compensated material at 292 K. The maximum achievable mobility for low-doped material in p-type 4H–SiC is shown to be 93 cm2/V s at room temperature.
Show PACS
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
61.72.up Other materials
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
72.20.My Galvanomagnetic and other magnetotransport effects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
72.80.Jc Other crystalline inorganic semiconductors

Molecular and solid-state (8-hydroxy-quinoline)aluminum interaction with magnesium: A first-principles study

S. Meloni, A. Palma, A. Kahn, J. Schwartz, and R. Car

J. Appl. Phys. 98, 023707 (2005); http://dx.doi.org/10.1063/1.1953869 (8 pages)

Online Publication Date: 21 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The interaction between Mg and (8-hydroxyquinoline)aluminum, Alq3, is investigated via ab initio molecular dynamics based on density-functional theory. We model the Alq3 thin film both with a single Alq3 molecule in vacuo (as is usually done in the literature) and with an Alq3 crystalline structure. Comparing the results from these two models, we show that bulk calculations provide a better description of the chemical processes involved, allowing the Mg atom to react with two neighboring Alq3 molecules, as was alluded to in a previous publication [ S. Meloni, A. Palma, A. Kahn, J. Schwartz, and R. Car, J. Am. Chem. Soc. 125, 7808 (2003) ]. Moreover, core-level shift calculations are in good agreement with experimental measurements only when using the solid phase approach. We also propose a different interpretation of the Al(2p) experimental core level presented in a previous work [ C. Shen, A. Kahn, and J. Schwartz, J. Appl. Phys. 89, 449 (2001) ].
Show PACS
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
61.66.Hq Organic compounds

Irradiation effects on the compensation of semi-insulating GaAs for particle detector applications

Anna Cavallini and Laura Polenta

J. Appl. Phys. 98, 023708 (2005); http://dx.doi.org/10.1063/1.1978989 (5 pages) | Cited 2 times

Online Publication Date: 21 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The distribution of the electric field and its spatial extent are key predictors of the charge collection efficiency of particle detectors. The electric field is strictly related to the electrically active defects, which are significantly modified by irradiation. In this paper we analyze the native and radiation-induced defects and infer the mechanisms controlling the electrical properties of semi-insulating GaAs Schottky diodes. The correlation between the electric-field distribution and deep levels confirms that the compensation mechanisms are mainly due to the donorlike centers and to their enhanced neutralization, which occurs for moderately high electric fields. Moreover, taking into account the charge balance among native and irradiation-induced defects, the active region extent is predicted.
Show PACS
61.82.Fk Semiconductors
61.80.Hg Neutron radiation effects
61.80.Jh Ion radiation effects
71.55.Eq III-V semiconductors
85.30.Kk Junction diodes
73.61.Ey III-V semiconductors

Formation of two-dimensional electron gases in polytypic SiC heterostructures

V. M. Polyakov and F. Schwierz

J. Appl. Phys. 98, 023709 (2005); http://dx.doi.org/10.1063/1.1984070 (6 pages) | Cited 17 times

Online Publication Date: 25 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The formation of two-dimensional electron gases (2DEGs) at polytypic (hexagonal/cubic) SiC heterojunctions (4H/3C SiC and 6H/3C SiC) is investigated by numerical self-consistent solutions of the Schrödinger and Poisson equations. The free-electron-density distributions and conduction-band profiles in the SiC heterostructures are calculated and compared to those occurring at AlGaN/GaN interfaces. Spontaneous and piezoelectric polarization effects in both SiC/SiC and AlGaN/GaN structures are taken into account. The combined effect of the polarization-induced bound charge and conduction-band offset between the hexagonal and cubic SiC polytypes results in the formation of 2DEGs with very high electron sheet concentration. 2DEG sheet densities about 20% larger than that in Al0.3Ga0.7N/GaN structures are calculated for 4H/3C SiC heterostructures. We also find that the 2DEG densities in the 4H/3C are much less sensitive to variations of the barrier layer thickness. The influence of the barrier doping layer on the 2DEG densities is also investigated.
Show PACS
81.05.Hd Other semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.20.At Surface states, band structure, electron density of states
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
77.22.Ej Polarization and depolarization
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.63.-b Electronic transport in nanoscale materials and structures
72.20.-i Conductivity phenomena in semiconductors and insulators
61.72.up Other materials

Study of structural-, compositional-, and thickness-dependent thermoelectric and electrical properties of Bi93Sb7 alloy thin films

Ramesh Chandra Mallik and V. Damodara Das

J. Appl. Phys. 98, 023710 (2005); http://dx.doi.org/10.1063/1.1957126 (8 pages) | Cited 2 times

Online Publication Date: 26 July 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have used the melt-quenching technique to prepare the bulk material and vapor-quenching technique to prepare the thin films of Bi93Sb7 alloy. The Bi93Sb7 alloy thin films of different thicknesses were grown onto well-cleaned glass and silicon substrates. The films were annealed at 150 ° C for 4 h in a vacuum of the order of 10−6 torr in order to remove the defects and to increase the grain size. The bulk and thin-film x-ray diffraction results agree with the transmission electron microscopy results and the compositional analysis of bulk by particle-induced x-ray emission and of thin films by Rutherford backscattering. The thickness and temperature dependences of thermoelectric power and electrical resistivity have been analyzed. The negative temperature coefficient of resistivity confirmed that the material is semiconducting in nature. The negative thermoelectric power confirmed that the present bismuth-rich material is a n type. In this paper we have made an attempt to study the thermoelectric properties of bulk as well as thin films of Bi93Sb7, maintaining the same composition. The scattering index parameter was calculated from the experimental data and was compared with the theoretical predictions of the size effect theory.
Show PACS
72.15.Jf Thermoelectric and thermomagnetic effects
73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
61.72.Cc Kinetics of defect formation and annealing
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
68.37.Lp Transmission electron microscopy (TEM)
Page 2 of 6 Pages Previous Page Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close