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19 Nov 2001

Volume 79, Issue 21, pp. 3383-3543

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Temporal measurement on and using pulses from spectrally narrowed emission in styrylpyridinium cyanine dye

Aditya K. Dharmadhikari, Achintya K. Bhowmik, Ayayi C. Ahyi, and Mrinal Thakur

Appl. Phys. Lett. 79, 3383 (2001); http://dx.doi.org/10.1063/1.1416166 (3 pages) | Cited 2 times

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Highly efficient spectrally narrowed emission (SNE) was observed in the solution of strylpyridinium cyanine dye (SPCD) pumped by fundamental and second harmonic of a picosecond Nd:YAG laser in two separate arrangements. A highly directional emission was observed in both the pumping arrangements without incorporating any mirrors. The pulse duration of the SNE was measured by background free SHG intensity autocorrelation technique. The measured duration of the pulses was 40 ps. These pulses, having a spectral linewidth of 10 nm (full width at half maximum), were used as a probe to measure the transient changes in the transmission in SPCD solution using a pump–probe setup. The transient optical transmission indicated a gain at the overlap and no gain was observed beyond a delay of 40 ps. © 2001 American Institute of Physics.
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78.40.Dw Liquids
78.55.Bq Liquids
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.47.-p Spectroscopy of solid state dynamics
78.40.Me Organic compounds and polymers

Low-threshold-current 1.32-μm GaInNAs/GaAs single-quantum-well lasers grown by molecular-beam epitaxy

Wei Li, Tomi Jouhti, Chang Si Peng, Janne Konttinen, Pekka Laukkanen, Emil-Mihai Pavelescu, Mihail Dumitrescu, and Markus Pessa

Appl. Phys. Lett. 79, 3386 (2001); http://dx.doi.org/10.1063/1.1418455 (3 pages) | Cited 51 times

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Using solid-source molecular-beam epitaxy with a rf-plasma source, we have grown GaInNAs/GaAs single-quantum-well lasers operating at 1.32 μm. For a broad-area oxide stripe, uncoated Fabry–Perot laser with a cavity length of 1600 μm, the threshold current density is 546 A/cm2 at room temperature. The internal quantum efficiency for these lasers is 80%, while the materials losses are 7.0 cm−1. A characteristic temperature of 104 K was measured in the temperature range from 20 to 80 °C. Optical output up to 40 mW per facet under continuous-wave operation was achieved for these uncoated lasers at room temperature. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Pk Continuous operation
81.05.Ea III-V semiconductors
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Generation of high energy femtosecond pulses from a side-pumped Yb-doped double-clad fiber laser

A. Hideur, T. Chartier, M. Brunel, S. Louis, C. Özkul, and F. Sanchez

Appl. Phys. Lett. 79, 3389 (2001); http://dx.doi.org/10.1063/1.1420487 (3 pages) | Cited 12 times

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We present a passively mode-locked side-pumped Yb-doped double-clad fiber laser, emitting around 1.05 μm. Polarization additive-pulse mode-locking technique is used. Mode locking is self-starting and produces 670 fs pulses after compression with a grating pair inserted in the cavity. The energy per pulse is 24 nJ. © 2001 American Institute of Physics.
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42.55.Wd Fiber lasers
42.60.Fc Modulation, tuning, and mode locking

Fabrication of two-dimensional photonic crystals using interference lithography and electrodeposition of CdSe

Ivan B. Divliansky, Atsushi Shishido, Iam-Choon Khoo, Theresa S. Mayer, David Pena, Suzushi Nishimura, Christine D. Keating, and Thomas E. Mallouk

Appl. Phys. Lett. 79, 3392 (2001); http://dx.doi.org/10.1063/1.1420584 (3 pages) | Cited 49 times

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This letter describes a simple synthetic approach to fabricate two-dimensional midinfrared CdSe photonic crystals (PC) by electrodeposition of CdSe in a polymer template defined using interference lithography. Characterization of the transmission spectra of CdSe PCs with a hexagonal array of 1.3 μm diameter and 2.7 μm pitch air voids showed a well-defined drop in transmission at 4.23 μm. The drop in transmission increased with incident angle, reaching a maximum of approximately 2.6 dB at 40° relative to the surface normal. This two-step synthetic approach can be used to incorporate photonic crystals onto arbitrary substrates for integration into future advanced optical circuits. © 2001 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.15.Pq Electrodeposition, electroplating
81.05.Dz II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
78.66.Hf II-VI semiconductors

Silicon-based photonic crystal heterostructure

Z. M. Jiang, B. Shi, D. T. Zhao, J. Liu, and Xun Wang

Appl. Phys. Lett. 79, 3395 (2001); http://dx.doi.org/10.1063/1.1421093 (3 pages) | Cited 14 times

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A silicon-based one-dimensional photonic crystal heterostructure is proposed, and its applications to an omnidirectional reflector and a transverse electric/transverse magnetic (TE/TM) splitter are illustrated. The photonic crystal heterostructure consists of two sets of multilayers, each has six periods of bilayers of poly-silicon and silicon dioxide. When the incident light comes from a medium with refractive index lower than 1.16, there is a frequency range over which of both TE and TM polarizations will be totally reflected at any incident angle. In such a case, the photonic crystal heterostructure can be used as a low loss omnidirectional dielectric reflector. However, when the refractive index of the medium is higher than 1.16, the heterostructure will serve as a good TE/TM splitter of very low crosstalk within certain ranges of light frequency and incident angle. © 2001 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Wc Optical coatings
42.70.Qs Photonic bandgap materials
42.79.Fm Reflectors, beam splitters, and deflectors
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Reduction of threading dislocation density in SiGe layers on Si (001) using a two-step strain–relaxation procedure

Akira Sakai, Ken Sugimoto, Takeo Yamamoto, Masahisa Okada, Hiroya Ikeda, Yukio Yasuda, and Shigeaki Zaima

Appl. Phys. Lett. 79, 3398 (2001); http://dx.doi.org/10.1063/1.1419037 (3 pages) | Cited 12 times

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A method to obtain high-quality strain–relaxed SiGe buffer layers on Si(001) substrates is presented. In this method, the strain relaxation of the SiGe layer is performed using a two-step procedure. Firstly, a low-temperature-grown SiGe layer, whose surface is covered by a thin Si cap layer, is thermally annealed. At this stage, the strain is incompletely relaxed and an atomically flat surface can be realized. Then, a second SiGe layer is grown on the first layer to achieve further strain relaxation. Transmission electron microscopy has clearly revealed that dislocations are dispersively introduced into the first SiGe/Si substrate interface and thus no pile up of dislocations occurs. The formation of a periodic undulation on the growth surface of the second SiGe layer is the key to inducing a drastic reduction in the threading dislocation density. © 2001 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.55.A- Nucleation and growth
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Lp Transmission electron microscopy (TEM)
81.40.Gh Other heat and thermomechanical treatments
68.37.Ps Atomic force microscopy (AFM)
68.35.Ct Interface structure and roughness

Agglomeration and percolation conductivity

K. Sieradzki, K. Bailey, and T. L. Alford

Appl. Phys. Lett. 79, 3401 (2001); http://dx.doi.org/10.1063/1.1419043 (3 pages) | Cited 31 times

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We report on results of agglomeration experiments for the Ag/SiO2/Si(100) system. Thin silver films, 100 nm in thickness, were annealed, and their electrical resistance was continuously monitored using a four-point probe technique. Scanning electron microscopy and digital image analysis were used to correlate the time-dependent agglomeration morphology to the sheet resistance of the Ag thin film. Our results indicated that the area fraction of the surface uncovered during agglomeration scaled linearly in time. We found that at fixed annealing temperature, the normalized sheet resistance followed power-law scaling in time, i.e., R ∼ ∣t−τ∣−μ, (μ = 1.25±0.1) where τ corresponds to the time it takes to reach electrical failure of the sample. © 2001 American Institute of Physics.
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73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Influence of alloy stability on the photoluminescence properties of GaAsN/GaAs quantum wells grown by molecular beam epitaxy

M.-A. Pinault and E. Tournié

Appl. Phys. Lett. 79, 3404 (2001); http://dx.doi.org/10.1063/1.1418263 (3 pages) | Cited 31 times

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We have investigated the influence of both the growth rate and the growth temperature on the structural and optical properties of GaAs0.972N0.028/GaAs single quantum wells grown by solid-source molecular beam epitaxy. The results are analyzed in light of the surface phase diagram obtained from in situ reflection high energy electron diffraction. We show that the best quality is achieved at the highest temperature below the onset of alloy decomposition. The use of high growth rates allows one to significantly increase the growth temperature. Our results demonstrate that it is the GaAsN alloy stability which governs the sample properties. © 2001 American Institute of Physics.
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68.65.Fg Quantum wells
78.67.De Quantum wells
81.07.St Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors

Phonon modes of GaNyP1−y (0.006 ⩽ y ⩽ 0.0285) measured by midinfrared spectroscopic ellipsometry

G. Leibiger, V. Gottschalch, A. Kasic, and M. Schubert

Appl. Phys. Lett. 79, 3407 (2001); http://dx.doi.org/10.1063/1.1419050 (3 pages) | Cited 10 times

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Midinfrared spectroscopic ellipsometry reveals the two-phonon mode behavior of GaNyP1−y for nitrogen compositions 0.006 ⩽ y ⩽ 0.0285. The single layers (∼350 nm) studied were grown by metalorganic vapor-phase epitaxy on GaP substrates with orientations (001), and (001) with 5° off toward [110]. Line-shape analysis of the midinfrared response allows determination of the transverse- and longitudinal-optical phonon frequencies of the GaP- and GaN-like phonon modes. The polar strength of the GaN lattice resonance increases linearly with y, which can be used to monitor the nitrogen content of GaNyP1−y. © 2001 American Institute of Physics.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
68.55.-a Thin film structure and morphology
07.60.Fs Polarimeters and ellipsometers
68.60.Wm Other nonelectronic physical properties

Electronegativity of the constituent rare-earth metals as a factor stabilizing the supercooled liquid region in Al-based metallic glasses

Dmitri V. Louzguine and Akihisa Inoue

Appl. Phys. Lett. 79, 3410 (2001); http://dx.doi.org/10.1063/1.1420781 (3 pages) | Cited 24 times

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The letter describes influence of the electronegativity of the constituent rare-earth metals on the supercooled liquid region in the Al–(Gd, Dy or Er)–Ni–Co metallic glasses. The samples were studied by x-ray diffractometry and differential scanning calorimetry. Calorimetry data for the La and Sm—bearing glasses studied earlier were also taken in consideration for comparison. It is found that supercooled liquid range in the Al85RE8Ni5Co2 alloys strongly depends upon electronegativity of the RE metal. © 2001 American Institute of Physics.
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61.43.Fs Glasses

Chemical role of oxygen plasma in wafer bonding using borosilicate glasses

D. M. Hansen, C. E. Albaugh, P. D. Moran, and T. F. Kuech

Appl. Phys. Lett. 79, 3413 (2001); http://dx.doi.org/10.1063/1.1418454 (3 pages) | Cited 2 times

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Plasma-treated oxide layers are commonly used in wafer bonding applications. Borosilicate glass (BSG) layers deposited by low-pressure chemical vapor deposition treated with an O2 plasma in reactive ion etching mode for 5 min at 0.6 W/cm2 and rinsed with DI H2O readily bond to GaAs and Si. The chemical role of this prebonding treatment was investigated using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The peak intensities for both the Si–O and B–O absorbance bands decreased in intensity as a result of the plasma treatment is consistent with the uniform sputtering of 9.8 nm±0.8 nm of BSG. Polarization dependent ATR-FTIR revealed that the H2O/OH absorbance bands decreased in peak intensity with the OH groups being preferentially oriented perpendicular to the sample surface after the plasma treatment. The subsequent DI H2O rinse restores the water to the surface while removing B2O3 from the BSG layer. This prebonding treatment, therefore, results in a hydrophilic bond, but alters the composition of the BSG film at the bonded interface. © 2001 American Institute of Physics.
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52.77.Bn Etching and cleaning
81.05.Kf Glasses (including metallic glasses)
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
81.65.Cf Surface cleaning, etching, patterning
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Direct observation of irradiation-induced nanocavity shrinkage in Si

X. F. Zhu, J. S. Williams, M. J. Conway, M. C. Ridgway, F. Fortuna, M.-O. Ruault, and H. Bernas

Appl. Phys. Lett. 79, 3416 (2001); http://dx.doi.org/10.1063/1.1413497 (3 pages) | Cited 12 times

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Nanocavities in Si substrates, formed by conventional H implantation and thermal annealing, are shown to evolve in size during subsequent Si irradiation. Both ex situ and in situ analytical techniques were used to demonstrate that the mean nanocavity diameter decreases as a function of Si irradiation dose in both the crystalline and amorphous phases. Potential mechanisms for this irradiation-induced nanocavity evolution are discussed. In the crystalline phase, the observed decrease in diameter is attributed to the gettering of interstitials. When the matrix surrounding the cavities is amorphized, cavity shrinkage may be mediated by one of two processes: nanocavities can supply vacancies into the amorphous phase and/or the amorphous phase may flow plastically into the nanocavities. Both processes yield the necessary decrease in density of the amorphous phase relative to crystalline material. © 2001 American Institute of Physics.
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81.05.Cy Elemental semiconductors
61.72.uf Ge and Si
85.40.Ry Impurity doping, diffusion and ion implantation technology
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.J- Point defects and defect clusters
52.77.Dq Plasma-based ion implantation and deposition
61.46.-w Structure of nanoscale materials

Improvement of CoSi2 thermal stability by cavity formation

A. Alberti, F. La Via, S. Ravesi, and E. Rimini

Appl. Phys. Lett. 79, 3419 (2001); http://dx.doi.org/10.1063/1.1420785 (3 pages) | Cited 5 times

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We propose a method to improve the thermal stability of thin CoSi2 layers on polycrystalline silicon substrates. Nitrogen atoms have been implanted at 55 keV to a dose of 5×1015/cm2 through a 70 nm silicide layer in order to locate the implanted peak near the silicide/silicon interface. The large band of cavities created at the interface has extended the thermal stability window by 125 °C with respect to the standard process. The improvement has been related to the silicide grain-boundary pinning due to the increase of the interface free energy contribution. © 2001 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
61.72.Mm Grain and twin boundaries
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
68.35.Md Surface thermodynamics, surface energies

Extending the epitaxial thickness limit in low-substrate-temperature- grown GaAs

G. Apostolopoulos, N. Boukos, A. Travlos, J. Herfort, and K. H. Ploog

Appl. Phys. Lett. 79, 3422 (2001); http://dx.doi.org/10.1063/1.1420783 (3 pages) | Cited 1 time

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A method for extending the epitaxial thickness limit in low-temperature-grown GaAs (LT-GaAs) is presented. It is shown that the use of vicinal GaAs(001) substrates with a high misorientation angle reduces the surface roughness of LT-GaAs and inhibits the nucleation of defects which cause the breakdown of perfect epitaxial growth. Kinetic Monte Carlo simulations are used to describe the influence of the vicinal substrate on the growth mode and to estimate the appropriate misorientation angle. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)

In as a surfactant for the growth of GaN (0001) by plasma-assisted molecular-beam epitaxy

C. Kruse, S. Einfeldt, T. Böttcher, and D. Hommel

Appl. Phys. Lett. 79, 3425 (2001); http://dx.doi.org/10.1063/1.1419232 (3 pages) | Cited 24 times

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The influence of indium on the surface morphology of GaN (0001) grown by plasma-assisted molecular-beam epitaxy (MBE) has been investigated. The rough and grain-like surface under nitrogen-rich growth conditions becomes smoother and similar to surfaces grown under gallium-rich conditions when a sufficiently high indium flux is used. However, the use of indium instead of gallium-rich conditions prevents the formation of gallium droplets on the surface which are associated with voids at their edges. Since indium is not incorporated into GaN for growth temperatures above 700 °C, it can be used as a surfactant in MBE growth of GaN. © 2001 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
82.70.Uv Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions)
52.77.Dq Plasma-based ion implantation and deposition
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Role of Ga flux in dislocation reduction in GaN films grown on SiC(0001)

C. D. Lee, Ashutosh Sagar, R. M. Feenstra, C. K. Inoki, T. S. Kuan, W. L. Sarney, and L. Salamanca-Riba

Appl. Phys. Lett. 79, 3428 (2001); http://dx.doi.org/10.1063/1.1421091 (3 pages) | Cited 27 times

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GaN films are grown by plasma-assisted molecular-beam epitaxy on SiC substrates. The width of the x-ray rocking curve for the (10math2) reflection exhibits a distinct minimum for Ga/N flux ratios which are only slightly greater than unity. Correlated with this minimum, the surface morphology is somewhat rough, with a hill and valley topography. Based on transmission electron micrographs, the reduction in rocking curve width is attributed to enhanced annihilation of edge dislocations due to their tendency to cluster at topographic valleys. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

High-quality Ge films on Si substrates using Sb surfactant-mediated graded SiGe buffers

J. L. Liu, S. Tong, Y. H. Luo, J. Wan, and K. L. Wang

Appl. Phys. Lett. 79, 3431 (2001); http://dx.doi.org/10.1063/1.1421092 (3 pages) | Cited 16 times

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High-quality Ge films were grown on Si substrates by solid-source molecular beam epitaxy using SiGe graded layer and Sb surfactant-mediation technique. Transmission electron microscopy measurements show that samples grown using this method have a lower threading dislocation density than those grown by other typical methods, such as grading at high temperature (700 °C) only, grading at intermediate temperature (510 °C) only, and the use of low temperature Si buffer. A relaxed Ge film on a 4-μm-thick graded buffer was grown and shown to have a threading dislocation density of 5.4×105 cm−2 and surface roughness of 35 Å. Ge p–i–n diodes were fabricated and tested. Under a reverse bias of 1 V, the p–i–n Ge mesa photodiodes exhibit a very low dark current density of 0.15 mA/cm2. © 2001 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
68.37.Lp Transmission electron microscopy (TEM)
61.72.Lk Linear defects: dislocations, disclinations
85.60.Dw Photodiodes; phototransistors; photoresistors

Analysis of gain saturation in In0.02Ga0.98N/In0.16Ga0.84N multiple quantum wells

K. Kyhm, R. A. Taylor, J. F. Ryan, T. Someya, and Y. Arakawa

Appl. Phys. Lett. 79, 3434 (2001); http://dx.doi.org/10.1063/1.1421094 (3 pages) | Cited 10 times

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A way of analyzing the data in a variable stripe length method gain experiment is presented. We confirm that the stripe length dependence of the gain in In0.02Ga0.98N/In0.16Ga0.84N multiple quantum wells is caused by the change of the chemical potential along the excited stripe due to the interaction of the carrier and photon densities, and the gain threshold density is estimated. A trial function assuming a Lorentzian line shape for the stripe length dependence of the gain is compared with the edge emission intensity as a function of the stripe length. This is found to fit very well with our data, even beyond the saturation region. © 2001 American Institute of Physics.
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78.67.De Quantum wells
78.45.+h Stimulated emission

Pump-power dependence of THz radiation from InAs surfaces under magnetic fields excited by ultrashort laser pulses

M. Migita and M. Hangyo

Appl. Phys. Lett. 79, 3437 (2001); http://dx.doi.org/10.1063/1.1420784 (3 pages) | Cited 12 times

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THz radiation from InAs surfaces excited by ultrashort laser pulses has been studied under low (∼0.6 μJ/cm2 fluence) and high (∼6 mJ/cm2 fluence) pump power densities. The THz radiation amplitude is affected in both cases. We found that the radiation wave form is broadened by applying magnetic fields for the low-density-excitation case whereas it is not for the high-density-excitation case. This result is explained by the difference of the effect of the magnetic field on the THz radiation due to the transient photocurrent and optical rectification effects. © 2001 American Institute of Physics.
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79.20.Ds Laser-beam impact phenomena
72.40.+w Photoconduction and photovoltaic effects
78.47.-p Spectroscopy of solid state dynamics
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors

Spatial variation of photoluminescence and related defects in InGaN/GaN quantum wells

M. S. Jeong, Y.-W. Kim, J. O. White, E.-K. Suh, M. G. Cheong, C. S. Kim, C.-H. Hong, and H. J. Lee

Appl. Phys. Lett. 79, 3440 (2001); http://dx.doi.org/10.1063/1.1420489 (3 pages) | Cited 23 times

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Spatially and spectrally resolved photoluminescence of InGaN/GaN quantum wells grown by metalorganic chemical vapor deposition is studied with near-field scanning optical microscopy (NSOM) and transmission electron microscopy (TEM). High-spatial-resolution NSOM images show bright blue quantum well emission around V defects and yellow emission inside the defects. TEM data suggest that the spatial distribution of blue luminescence is partly due to dislocation gettering by V defects. The yellow emission is attributed to the Ga vacancy-impurity complexes trapped inside V defects. © 2001 American Institute of Physics.
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78.67.De Quantum wells
73.20.Hb Impurity and defect levels; energy states of adsorbed species
78.55.Cr III-V semiconductors
71.55.Eq III-V semiconductors
73.21.Fg Quantum wells
61.72.Yx Interaction between different crystal defects; gettering effect

Instability of hydrogenated amorphous carbon films towards defect creation at high disorder

M. Lejeune, R. Bouzerar, M. Benlahsen, O. Durand-Drouhin, and A. Zeinert

Appl. Phys. Lett. 79, 3443 (2001); http://dx.doi.org/10.1063/1.1415046 (3 pages) | Cited 4 times

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We report a complete characterization of hydrogenated amorphous carbon (a-C:H) thin films through Raman spectroscopy, photothermal deflection spectroscopy, and mechanical studies. The interpretation of the optical absorption data within the Dasgupta’s model offers an estimate of the disorder intensity through a characteristic energy scale of the model. The vibrational data (Raman spectra) and the stress data together with the optical absorption data give strong evidence for a sharp transition between a low disorder state dominated by aromatic rings and a strong disorder state likely in keeping with the creation of some topological defects, such as odd rings. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.43.Dq Amorphous semiconductors, metals, and alloys
78.66.Jg Amorphous semiconductors; glasses
68.60.Bs Mechanical and acoustical properties
81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.40.Pg Disordered solids
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
71.55.Jv Disordered structures; amorphous and glassy solids
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Electron field emission from sulfur-incorporated nanocrystalline carbon thin films

S. Gupta, B. L. Weiss, B. R. Weiner, and G. Morell

Appl. Phys. Lett. 79, 3446 (2001); http://dx.doi.org/10.1063/1.1411988 (3 pages) | Cited 11 times

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Results are reported on the electron field emission properties of sulfur-incorporated nanocrystalline carbon (n-C:S) thin films grown by hot-filament chemical vapor deposition technique. The lowest turn-on field values observed were around 4.0–4.5 V/μm, which are about half of those measured for films grown without sulfur. Associated to the effect of addition of sulfur on field emission properties, there are interesting microstructural changes, as characterized with scanning electron microscopy, atomic force microscopy, and Raman spectroscopy techniques. The sulfur-incorporated films show smoother and finer-grained surfaces than those grown without sulfur. These results are similar to those found for the introduction of nitrogen, but different to those produced by oxygen addition to the chemical vapor deposition process. These findings are attributed to changes in the electronic band structure. © 2001 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
85.45.Db Field emitters and arrays, cold electron emitters
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.07.Bc Nanocrystalline materials
68.55.-a Thin film structure and morphology
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Ps Atomic force microscopy (AFM)
78.30.Am Elemental semiconductors and insulators

Indium-surfactant-assisted growth of high-mobility AlN/GaN multilayer structures by metalorganic chemical vapor deposition

S. Keller, S. Heikman, I. Ben-Yaacov, L. Shen, S. P. DenBaars, and U. K. Mishra

Appl. Phys. Lett. 79, 3449 (2001); http://dx.doi.org/10.1063/1.1420573 (3 pages) | Cited 17 times

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AlN/GaN single and multilayer structures with various AlN and GaN layer thicknesses were grown by metalorganic chemical vapor deposition. Step flow growth of AlN was achieved using trimethylindium as a surfactant. Defect formation in the AlN layer could be largely prevented for AlN layers thinner than 2.9 nm. In the multiquantum-well samples, which consisted of five (AlN/GaN) periods, a two-dimensional electron gas (2DEG) was formed at the interface between the GaN base layer and the first AlN barrier layer. When the thickness of the AlN barrier layer in the multiquantum well was increased from 0.9 to 2.6 nm at a constant GaN well thickness of 5 nm, the sheet carrier density of the 2 DEG increased from 5×1012 to 2.1×1013 cm−2 and the electron mobility measured at 77 K decreased from 11780 to 3140 cm2/V s. The effect of the GaN well thickness was also investigated. © 2001 American Institute of Physics.
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81.07.St Quantum wells
68.65.Fg Quantum wells
73.63.Hs Quantum wells
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Characterization of high dose Fe implantation into p-GaN

N. Theodoropoulou, A. F. Hebard, S. N. G. Chu, M. E. Overberg, C. R. Abernathy, S. J. Pearton, R. G. Wilson, and J. M. Zavada

Appl. Phys. Lett. 79, 3452 (2001); http://dx.doi.org/10.1063/1.1420406 (3 pages) | Cited 34 times

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High concentrations (3–5 at. %) of Fe were incorporated into p-GaN by direct implantation at elevated substrate temperature (350 °C). Subsequent annealing at 700 °C produced apparent ferromagnetic behavior up to ∼250 K for the 3 at. % sample. Selected area diffraction patterns did not reveal the presence of any other phases in the Fe-implanted region. The direct implantation process appears promising for examining the properties of magnetic semiconductors with application to magnetotransport and magneto-optical devices. © 2001 American Institute of Physics.
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75.50.Pp Magnetic semiconductors
61.72.uj III-V and II-VI semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.Cc Kinetics of defect formation and annealing

Millisecond phosphorescence of free electrons in pure GaAs

A. M. Gilinsky and K. S. Zhuravlev

Appl. Phys. Lett. 79, 3455 (2001); http://dx.doi.org/10.1063/1.1420575 (3 pages) | Cited 6 times

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A very long decay of transient free-to-bound photoluminescence (PL) in pure GaAs at low temperatures has been experimentally found. It is shown that, in undoped or dilutely doped GaAs, the decay of band-to-acceptor PL after a transient excitation follows an essentially nonexponential dependence approximated by a power law with the exponent as low as 0.3, and is observed for as long as 2.5 ms. The long decays of free-electron PL point to the domination of repeated trappings and subsequent releases of free electrons by some shallow traps, which are suggested to be the shallow donors. © 2001 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
71.55.Eq III-V semiconductors
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