APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

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

20 Dec 2004

Volume 85, Issue 25, pp. 6083-6293

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 6281 (2004); http://dx.doi.org/10.1063/1.1834720 (3 pages)

M. P. Rao, M. F. Aimi, and N. C. MacDonald
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

Persistent photocurrent spectroscopy of GaN metal–semiconductor–metal photodetectors on long time scale

B. Potì, A. Passaseo, M. Lomascolo, R. Cingolani, and M. De Vittorio

Appl. Phys. Lett. 85, 6083 (2004); http://dx.doi.org/10.1063/1.1840122 (3 pages) | Cited 8 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Some of the trapping mechanisms responsible for the persistent photocurrent effects in GaN metal–semiconductor–metal photodetectors have been studied on a time scale of several hours by analyzing the photocurrent decay kinetic as a function of temperature. The analysis of the Arrhenius plot of the decay kinetic on a long time scale shows two activation energies of about 140 meV and 1 eV. Such values are in good agreement with two slope changes observed in the room temperature photocurrent spectrum around 2.40 and 3.25 eV, in the GaN energy band gap. According to the Lucovsky theory the 140 meV activation energy was interpreted as due to the transition from a deep localized state to the conduction band edge, whereas the 1 eV activation energy was interpreted as due to the transition from the valence band edge to a deep localized state. Therefore, the persistent photocurrent on long time scale is primarily due to the presence of donor deep and acceptor deep states generated by gallium vacancies, gallium antisites, and carbon impurities.
Show PACS
85.60.Gz Photodetectors (including infrared and CCD detectors)
71.55.Eq III-V semiconductors
73.40.Sx Metal-semiconductor-metal structures
72.40.+w Photoconduction and photovoltaic effects
61.72.J- Point defects and defect clusters

Application of modified transmission line model to measure p-type GaN contact

N. C. Chen, C. Y. Tseng, A. P. Chiu, C. F. Shih, and P. H. Chang

Appl. Phys. Lett. 85, 6086 (2004); http://dx.doi.org/10.1063/1.1835993 (3 pages) | Cited 10 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This work presented a procedure for extending the modified transmission line model to measure non-ohmic contact. This method was applied to the p-type GaN contact with the resulting sheet resistance similar to that determined by the Hall measurement. The voltage–current density (V–J) curve obtained using this procedure was also similar to that by directly analyzing the current–voltage curve of a light-emitting diode. Both results revealed the validity of this procedure. Rather than yielding a specific contact resistance for an ohmic contact, this procedure yielded a V–J curve to describe the non-ohmic contact characteristics. Similarly, this procedure could also extend the linear transmission line model to the analysis of non-ohmic contacts.
Show PACS
73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
73.61.Ey III-V semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects

Properties of defect modes in one-dimensional photonic crystals containing a defect layer with a negative refractive index

Kun-yuan Xu, Xiguang Zheng, and Wei-long She

Appl. Phys. Lett. 85, 6089 (2004); http://dx.doi.org/10.1063/1.1824175 (3 pages) | Cited 9 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The band structures of one-dimensional photonic crystals containing a defect layer with a negative refractive index are studied, showing that the defect modes possess three types of dispersion: positive, zero, and negative types. The zero and negative dispersion phenomena may be useful in the design of large incident angle filters and narrow frequency and sharp angular filters, respectively. The dispersion multiplicity of the defect modes can be understood by an approximate formula. Moreover, the splitting of one defect mode into multiple defect modes is observed in the band gap when the parameters of the defect layer vary. This phase transition phenomenon may be useful in the design of multiple channeled filters or filters with a rectangular profile. The condition for the critical point of the phase transition is also analyzed.
Show PACS
42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Direct optoelectronic generation and detection of sub-ps-electrical pulses on sub-mm-coaxial transmission lines

Tae-In Jeon and D. Grischkowsky

Appl. Phys. Lett. 85, 6092 (2004); http://dx.doi.org/10.1063/1.1839645 (3 pages) | Cited 25 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report efficient direct optoelectronic generation of sub-ps-THz pulses on 50 Ω coaxial transmission lines with a 330 μm diameter solid copper outer tube filled with Teflon containing the 80 μm diameter inner conductor. The transmitted pulses after propagating as much as 105 mm were measured at the end of the line with an optoelectronic antenna having sub-ps-time resolution. We observed low-loss, single transverse electromagnetic mode propagation with very little group velocity dispersion. The experimentally derived values for the frequency-dependent absorption are consistent with the theoretical predictions.
Show PACS
84.40.Az Waveguides, transmission lines, striplines
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Electrically switchable lasing from pyrromethene 597 embedded holographic-polymer dispersed liquid crystals

Rachel Jakubiak, Lalgudi V. Natarajan, Vincent Tondiglia, Guang S. He, Paras N. Prasad, Timothy J. Bunning, and Richard A. Vaia

Appl. Phys. Lett. 85, 6095 (2004); http://dx.doi.org/10.1063/1.1839282 (3 pages) | Cited 22 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
One-dimensional photonic band gap (PBG) materials created from holographic polymer dispersed liquid crystals (H-PDLCs) provide enhanced light localization in an organic electro-optic device. Distributed feedback within the reflection notch of a H-PDLC grating narrowed the bandwidth of pyrromethene 597 fluorescence from 56 to 8.4 nm at a lasing threshold of 0.12 mJ cm−2, compared to 2.6 mJ cm−2 required to observe amplified spontaneous emission in a nonstructured, but comparable floodlit (PDLC) sample. Application of an electric field (10–40 V∕μm) continuously decreased the diffraction efficiency of the grating and the commensurate dynamic lasing intensity thus demonstrating electrically modulated gain from an optically pumped, all-organic PBG.
Show PACS
42.70.Df Liquid crystals
42.70.Qs Photonic bandgap materials
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.55.Tv Photonic crystal lasers and coherent effects
42.40.Eq Holographic optical elements; holographic gratings
78.55.Kz Solid organic materials

Ion-exchanged waveguides in glass doped with PbS quantum dots

Jason M. Auxier, Michael M. Morrell, Brian R. West, Seppo Honkanen, Axel Schülzgen, Nasser Peyghambarian, Sabyasachi Sen, and Nicholas F. Borrelli

Appl. Phys. Lett. 85, 6098 (2004); http://dx.doi.org/10.1063/1.1839284 (3 pages) | Cited 5 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The lowest-loss (≲1 dB∕cm) ion-exchanged waveguides in glass doped with PbS quantum dots are presented. Near-field mode profile and refractive index profile using the refracted near-field technique were measured for these waveguides. We demonstrate that the optical properties of this glass remain unchanged during the ion-exchange process.
Show PACS
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
42.79.Gn Optical waveguides and couplers
78.67.Hc Quantum dots
61.43.Fs Glasses
78.55.Qr Amorphous materials; glasses and other disordered solids
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Ce Glasses, quartz

Microsphere whispering-gallery-mode laser using HgTe quantum dots

S. I. Shopova, G. Farca, A. T. Rosenberger, W. M. S. Wickramanayake, and N. A. Kotov

Appl. Phys. Lett. 85, 6101 (2004); http://dx.doi.org/10.1063/1.1841459 (3 pages) | Cited 32 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ultralow-threshold continuous-wave lasing is achieved at room temperature in a fused-silica microsphere that is coated with HgTe quantum dots (colloidal nanoparticles). The 830 nm pump input and HgTe microlaser output are efficiently coupled into and out of whispering-gallery modes by tapered fibers. Lasing occurs at wavelengths ranging from 1240 to 1780 nm, depending on the size and composition of the quantum dots (HgCdTe is also used). A linear fit to the data determines the lowest observed threshold pump power to be 0±2 μW.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
78.67.Hc Quantum dots
78.55.Et II-VI semiconductors

Stimulated emission and optical gain in LaF3:Nd nanoparticle-doped polymer-based waveguides

R. Dekker, D. J. W. Klunder, A. Borreman, M. B. J. Diemeer, K. Wörhoff, A. Driessen, J. W. Stouwdam, and F. C. J. M. van Veggel

Appl. Phys. Lett. 85, 6104 (2004); http://dx.doi.org/10.1063/1.1840110 (3 pages) | Cited 30 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report experiments which show evidence that stimulated emission at 863 nm takes place in hybrid monomode Si3N4 waveguides where LaF3:Nd nanoparticle-doped polymethylmethacrylate (PMMA) was used as a top cladding material. Furthermore, optical gain at 1319 nm in LaF3:Nd nanoparticle dispersed PMMA (0.1 dB∕cm) and photodefinable epoxy (Microchem SU-8) multimode waveguides has been observed at pump powers below 10 mW. This class of composite materials based on polymers with dispersed nanoparticles shows promising properties for planar optical amplifiers. Simulation showed that optical gain in the order of 10 dB can be achieved at 100 mW pump power in a 20 cm long monomode waveguide.
Show PACS
78.45.+h Stimulated emission
42.79.Gn Optical waveguides and couplers
42.70.Jk Polymers and organics
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
42.82.-m Integrated optics

The evolution of electroluminescence in Ge quantum-dot diodes with the fold number

Y. H. Peng, Chih-Hsiung Hsu, C. H. Kuan, C. W. Liu, P. S. Chen, M.-J. Tsai, and Y. W. Suen

Appl. Phys. Lett. 85, 6107 (2004); http://dx.doi.org/10.1063/1.1842371 (3 pages) | Cited 7 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electroluminescence of the light-emitting diodes with five-, ten and 30-fold p-type Ge quantum dots grown on n+ Si substrates is studied. The enhanced integral electroluminescence intensity and blueshift of the 30-fold one at high temperature (>200 K) act contrary to those in five- and ten-fold ones. It is attributed to the emission in the higher-fold quantum dots enabled by the injected electrons diffusing the farther at the higher temperature. Transmission electron microscopy shows that the size of the Ge quantum dots and the Si component in them, both increase with increasing the fold number. Due to the strain-induced intermixing at the high-fold quantum dots, those dots hence have large band gap and result in the intensity increment and blueshift at the high temperature.
Show PACS
85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.60.Fi Electroluminescence
68.37.Lp Transmission electron microscopy (TEM)

Guiding 1.5 μm light in photonic crystals based on dielectric rods

Solomon Assefa, Peter T. Rakich, Peter Bienstman, Steven G. Johnson, Gale S. Petrich, John D. Joannopoulos, Leslie A. Kolodziejski, Erich P. Ippen, and Henry I. Smith

Appl. Phys. Lett. 85, 6110 (2004); http://dx.doi.org/10.1063/1.1840107 (3 pages) | Cited 25 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Photonic-crystal structures consisting of dielectric rods were designed, fabricated, and optically characterized. The combination of the high refractive-index-contrast GaAs∕AlxOy material system with electron-beam lithography enabled the fabrication of structures suitable for the optical propagation of 1.5 μm light. Experimental transmission spectra were obtained for structures consisting of a two-dimensional array of rods and line-defect waveguides. Optical measurements confirmed the presence of a photonic band gap, as well as band gap guidance in the line-defect waveguide. A two-stage coupling scheme facilitated efficient optical coupling into the line-defect waveguide.
Show PACS
42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
42.82.Cr Fabrication techniques; lithography, pattern transfer

Demonstration of ultra-high-Q small mode volume toroid microcavities on a chip

T. J. Kippenberg, S. M. Spillane, and K. J. Vahala

Appl. Phys. Lett. 85, 6113 (2004); http://dx.doi.org/10.1063/1.1833556 (3 pages) | Cited 39 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Optical microcavities confine light spatially and temporally and find application in a wide range of fundamental and applied studies. In many areas, the microcavity figure of merit is not only determined by photon lifetime (or the equivalent quality-factor, Q), but also by simultaneous achievement of small mode volume (V). Here we demonstrate ultra-high Q-factor small mode volume toroid microcavities on-a-chip, which exhibit a Q∕V factor of more than 106 (λ∕n)−3. These values are the highest reported to date for any chip-based microcavity. A corresponding Purcell factor in excess of 200 000 and a cavity finesse of >2.8×106 is achieved, demonstrating that toroid microcavities are promising candidates for studies of the Purcell effect, cavity QED or biochemical sensing.
Show PACS
42.79.-e Optical elements, devices, and systems
07.60.-j Optical instruments and equipment

Coherent plasmons in InSb

Michael P. Hasselbeck, L. A. Schlie, and D. Stalnaker

Appl. Phys. Lett. 85, 6116 (2004); http://dx.doi.org/10.1063/1.1840118 (3 pages) | Cited 2 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Far-infrared electromagnetic radiation is emitted by coherent plasmon oscillations in bulk (111) InSb. The oscillations are excited by near-infrared ultrashort laser pulses and characterized as a function of temperature. The coherent plasmon frequency is determined by the intrinsic electron concentration and donor doping density. The amplitude of the oscillations decreases with increasing temperature due to a weakening of the photo-Dember starting mechanism.
Show PACS
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics

A microfluidic 2×2 optical switch

Kyle Campbell, Alex Groisman, Uriel Levy, Lin Pang, Shayan Mookherjea, Demetri Psaltis, and Yeshaiahu Fainman

Appl. Phys. Lett. 85, 6119 (2004); http://dx.doi.org/10.1063/1.1839281 (3 pages) | Cited 26 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A 2×2 microfluidic-based optical switch is proposed and demonstrated. The switch is made of an optically clear silicon elastomer, Polydimethylsiloxane (PDMS), using soft lithography. It has insertion loss smaller than 1 dB and extinction ratio on the order of 20 dB. The device is switching between transmission (bypass) and reflection (exchange) modes within less than 20 ms.
Show PACS
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.82.Gw Other integrated-optical elements and systems

Operating characteristics of a traveling-wave semiconducting polymer optical amplifier

G. Heliotis, D. D. C. Bradley, M. Goossens, S. Richardson, G. A. Turnbull, and I. D. W. Samuel

Appl. Phys. Lett. 85, 6122 (2004); http://dx.doi.org/10.1063/1.1835555 (3 pages) | Cited 11 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report a study of light amplification in dilute solutions of the semiconducting polymer poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). The operating characteristics of the F8BT solution amplifier are investigated in detail, and we show that it provides a large optical gain (>40 dB∕cm) across a wide (>48 nm) spectral bandwidth in the green. The saturation characteristics of the amplifier are found to be in excellent agreement with theoretical predictions, allowing an estimate of the F8BT stimulated emission cross-section, σ. We find σ∼1.7×10−16 cm2, comparable with the reported values for established laser dyes and other high-gain conjugated polymers.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.70.Jk Polymers and organics
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption

Diffraction by an optical fractal grating

Bo Hou, Gu Xu, Weijia Wen, and George K. L. Wong

Appl. Phys. Lett. 85, 6125 (2004); http://dx.doi.org/10.1063/1.1840112 (3 pages) | Cited 8 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report experimental and theoretical studies of Fraunhofer diffraction pattern of a 15-level H-fractal grating. The diffraction pattern was found to exhibit self-similarity. In particular, the diffracted light was found to be more intense at higher spatial frequencies than at lower frequencies, in stark contrast to the diffraction patterns of wire gratings and grid gratings. Using Fourier transform theory, we show that this unusual behavior comes from the structural coherence of the H-fractal, which makes it favorable to use higher-order diffraction spectra for larger dispersion. In addition, the fractal dimension of the grating is shown analytically and experimentally to be two.
Show PACS
42.25.Fx Diffraction and scattering
42.79.Dj Gratings
42.30.Kq Fourier optics
42.25.Kb Coherence

Photoluminescence and polarized photodetection of single ZnO nanowires

Zhiyong Fan, Pai-chun Chang, Jia G. Lu, Erich C. Walter, Reginald M. Penner, Chien-hung Lin, and Henry P. Lee

Appl. Phys. Lett. 85, 6128 (2004); http://dx.doi.org/10.1063/1.1841453 (3 pages) | Cited 122 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Single crystal ZnO nanowires are synthesized and configured as field-effect transistors. Photoluminescence and photoconductivity measurements show defect-related deep electronic states giving rise to green-red emission and absorption. Photocurrent temporal response shows that current decay time is significantly prolonged in vacuum due to a slower oxygen chemisorption process. The photoconductivity of ZnO nanowires is strongly polarization dependent. Collectively, these results demonstrate that ZnO nanowire is a remarkable optoelectronic material for nanoscale device applications.
Show PACS
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Et II-VI semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.43.Mn Adsorption kinetics
61.46.-w Structure of nanoscale materials

In-rich In1−xGaxN films by metalorganic vapor phase epitaxy

Chin-An Chang, Chuan-Feng Shih, Nai-Chuan Chen, T. Y. Lin, and Kuo-Shiun Liu

Appl. Phys. Lett. 85, 6131 (2004); http://dx.doi.org/10.1063/1.1842375 (3 pages) | Cited 17 times

Online Publication Date: 15 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Single crystalline In1−xGaxN films containing high In content (70%–100%) were grown by metalorganic vapor phase epitaxy. A linear relation was observed between the lattice constants and gas phase Ga∕In ratios. The surface morphology changed from pyramid for InN to more planar ones for the InGaN alloys with increasing Ga content. The electron mobility decreased rapidly from 1200 cm2∕V s for InN to less than 100 cm2∕V s for In0.7Ga0.3N, with a carrier concentration of low- 1019 cm−3 for all the as-grown films. Using photoluminescence a single emission peak was observed at 1.4–1.6 μm for the In-rich InGaN with decreasing wavelengths up to below 20% of Ga. Two peaks were observed for the In0.80Ga0.20N, however, indicating possible phase separation. The x-ray photoelectron spectroscopic measurement showed shifts to higher binding energies for both In and Ga with increasing Ga content. The estimated alloy composition, however, depended sensitively on the sputtering conditions of the samples.
Show PACS
81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.60.Dp Adsorbed layers and thin films
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close