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28 Dec 1998

Volume 73, Issue 26, pp. 3803-3961

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Buried heterostructure InGaAsP/InP strain-compensated multiple quantum well laser with a native-oxidized InAlAs current blocking layer

Zhi Jie Wang, Soo-Jin Chua, Fan Zhou, Wei Wang, and Rong Han Wu

Appl. Phys. Lett. 73, 3803 (1998); http://dx.doi.org/10.1063/1.122899 (3 pages) | Cited 3 times

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An InAlAs native oxide is used to replace the p-n reverse-biased junction in a conventional buried heterostructure InP-based laser. This technique reduces the number of regrowth steps and eliminates leakage current under high-temperature operation. The InAlAs native oxide buried heterostructure (NOBH) laser with strain-compensated InGaAsP/InP multiple quantum well active layers has a threshold current of 5.6 mA, a slope efficiency of 0.23 mW/mA, and a linear power up to 22.5 mW with a HR-coated facet. It exhibits single transverse mode with lasing wavelength at 1.532 μm. A characteristic temperature (T0) of 50 K is obtained from the NOBH laser with a nonoptimized oxide layer width. © 1998 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes

Growth of nonlinear optical thin films of KTa1−xNbxO3 on GaAs by pulsed laser deposition for integrated optics

L. A. Knauss, K. S. Harshavardhan, H.-M. Christen, H. Y. Zhang, X. H. He, Y. H. Shih, K. S. Grabowski, and D. L. Knies

Appl. Phys. Lett. 73, 3806 (1998); http://dx.doi.org/10.1063/1.122900 (3 pages) | Cited 10 times

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We report successful deposition of epitaxial nonlinear KTa0.52Nb0.48O3 (KTN) films on (100) GaAs substrates. A buffer layer scheme consisting of epitaxial MgO and SrTiO3 buffer layers and a Si3Ni4 encapsulation of the substrate was developed to alleviate chemical and structural incompatibilities between the GaAs substrate and KTN film at the growth temperature (∼750 °C). The structure, composition, and preliminary optical properties of the KTN films were evaluated by four-circle x-ray diffraction, Rutherford backscattering spectrometry, and prism coupled optical waveguide mode measurements, respectively. We observed sharp and distinguishable transverse electric and transverse magnetic propagating modes in the KTN films, and measured the refractive index (n0) of the film at 488 nm to be 2.275 which is close to the bulk value of 2.35, all of which indicates a high structural and optical film quality. © 1998 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
42.65.Wi Nonlinear waveguides
42.82.Et Waveguides, couplers, and arrays
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Mp Nonlinear optical crystals
42.79.Wc Optical coatings

Large enhancement in quasiphase matched second-harmonic generation efficiency by an external temperature gradient

Ranjit D. Pradhan and Noureddine Melikechi

Appl. Phys. Lett. 73, 3809 (1998); http://dx.doi.org/10.1063/1.122901 (3 pages) | Cited 2 times

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We show that for continuous wave second-harmonic generation using quasiphase matching in periodically segmented waveguides, thermal loading caused by the fundamental and the generated beams degrades the quasiphase matching condition which corrupts the spectral quality of the second-harmonic field. We also show that a carefully designed external temperature gradient leads to an enhancement of the conversion efficiency and control of the spectral line shape of the output field. Compared to earlier work, our simple scheme yields an enhancement of the second-harmonic conversion efficiency by a factor of 2–4 depending on the input fundamental power. © 1998 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays

Effect of detuning on the angular emission pattern of high-efficiency microcavity light-emitting diodes

C. Dill, R. P. Stanley, U. Oesterle, D. Ochoa, and M. Ilegems

Appl. Phys. Lett. 73, 3812 (1998); http://dx.doi.org/10.1063/1.122902 (3 pages) | Cited 10 times

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Results on molecular beam epitaxy-grown microcavity light-emitting diodes with InGaAs/GaAs quantum wells and a hybrid top mirror are presented. An external quantum efficiency of 14.8% is achieved for a 400 μm diam light-emitting diode. The strong influence of the spectral overlap between the spontaneous emission spectrum and the cavity resonance mode on the radiation pattern is shown. The angular emission profile is compared with model predictions for different detunings, and a very good agreement is obtained when the asymmetric spectral broadening of the intrinsic spontaneous emission is taken into account. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.60.Jb Light-emitting devices
42.55.Px Semiconductor lasers; laser diodes
73.61.Ey III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.By Design of specific laser systems

Island size effects in nanoparticle-enhanced photodetectors

Howard R. Stuart and Dennis G. Hall

Appl. Phys. Lett. 73, 3815 (1998); http://dx.doi.org/10.1063/1.122903 (3 pages) | Cited 106 times

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We report the effect of metal-island size variation in nanoparticle-enhanced photodetectors. Nanoparticle size was controlled by varying the deposition and annealing conditions used to produce the metal-island films. Increasing the size of silver-island particles fabricated onto 165 nm thick silicon-on-insulator (SOI) photodetectors resulted in a dramatic increase in the observed photocurrent. A nearly factor-of-20 photocurrent enhancement was observed for light of wavelength 800 nm, a significant improvement over previously reported results. The improvement is linked to two physical effects: the increased scattering efficiency of the larger nanoparticles and a qualitative change in the resonance characteristics of the metal-island film due to radiative coupling to the SOI waveguide modes. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
78.66.Bz Metals and metallic alloys
78.40.Kc Metals, semimetals, and alloys
73.50.Mx High-frequency effects; plasma effects
73.40.Sx Metal-semiconductor-metal structures

Saturation of intraband absorption and electron relaxation time in n-doped InAs/GaAs self-assembled quantum dots

S. Sauvage, P. Boucaud, F. Glotin, R. Prazeres, J.-M. Ortega, A. Lemaître, J.-M. Gérard, and V. Thierry-Flieg

Appl. Phys. Lett. 73, 3818 (1998); http://dx.doi.org/10.1063/1.122904 (4 pages) | Cited 22 times

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We have observed the saturation of intraband absorption in InAs/GaAs self-assembled quantum dots. The investigated n-doped self-assembled quantum dots exhibit an intraband absorption within the conduction band, which is peaked at an 8 μm wavelength. The saturation of the intraband absorption is achieved with an infrared pump delivered by a pulsed free-electron laser. The saturation of the transition is observed for an intensity around ≈0.6 MW cm−2. The electron relaxation time under intraband excitation is measured by time-resolved pump–probe experiments. An electron relaxation time T1 ≈ 3 ps is reported. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Simultaneous sampling of optical pulse intensities and wavelengths by four-wave mixing in a semiconductor optical amplifier

S. Diez, C. Schmidt, D. Hoffmann, C. Bornholdt, B. Sartorius, H. G. Weber, L. Jiang, and A. Krotkus

Appl. Phys. Lett. 73, 3821 (1998); http://dx.doi.org/10.1063/1.122905 (3 pages) | Cited 5 times

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An all-optical sampling technique that allows the simultaneous measurement of optical pulse intensities and wavelengths with a temporal resolution of about 1 ps is introduced. Using four-wave mixing (FWM) in a semiconductor optical amplifier, the optical signal under test is cross correlated with nearly transform-limited 1.4 ps optical sampling pulses. While the intensity of the generated FWM signal is used to determine the temporal shape of the signal intensity, the wavelength of the FWM signal yields time-resolved information about the signal wavelength (i.e., the frequency chirp). Using this technique, the correlation of intensity and wavelength dynamics of pulses generated by a self-Q-switched distributed-feedback laser is determined directly. © 1998 American Institute of Physics.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers

Generation and detection of coherent terahertz waves using two photomixers

S. Verghese, K. A. McIntosh, S. Calawa, W. F. Dinatale, E. K. Duerr, and K. A. Molvar

Appl. Phys. Lett. 73, 3824 (1998); http://dx.doi.org/10.1063/1.122906 (3 pages) | Cited 74 times

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A general technique has been demonstrated at microwave and submillimeter-wave frequencies for photoconductive sampling in the frequency domain using photomixers and continuous-wave laser diodes. A microwave version in which two photomixers were coupled by a transmission line was developed to quantitatively test the concept from 0.05 to 26.5 GHz. A quasioptical version using antenna-coupled photomixers was demonstrated from 25 GHz to 2 THz. Such a system can outperform systems based on time-domain photoconductive sampling in frequency resolution, spectral brightness, system size, and cost.
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84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
84.40.Ba Antennas: theory, components and accessories
72.40.+w Photoconduction and photovoltaic effects
85.60.Gz Photodetectors (including infrared and CCD detectors)

Single-wall carbon nanotubes synthesized by laser ablation in a nitrogen atmosphere

Y. Zhang, H. Gu, and S. Iijima

Appl. Phys. Lett. 73, 3827 (1998); http://dx.doi.org/10.1063/1.122907 (3 pages) | Cited 26 times

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The products of laser ablation of graphite in a nitrogen atmosphere have been studied by transmission electron microscopy and electron energy-loss spectroscopy. Using nickel and cobalt as catalyst, single-wall carbon nanotubes can be produced with a yield similar to that obtained in an inert gas. Nitrogen has not been found in the nanotubes and crystallized fullerenes although it has been detected in amorphous carbon. A growth model has been proposed to explain the experimental results. © 1998 American Institute of Physics.
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81.05.ub Fullerenes and related materials
81.15.Fg Pulsed laser ablation deposition
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
79.20.Kz Other electron-impact emission phenomena

Noncascaded intersubband injection lasers at λ ≈ 7.7 μm

Claire Gmachl, Federico Capasso, Alessandro Tredicucci, Deborah L. Sivco, Albert L. Hutchinson, S. N. George Chu, and Alfred Y. Cho

Appl. Phys. Lett. 73, 3830 (1998); http://dx.doi.org/10.1063/1.122908 (3 pages) | Cited 10 times

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The realization of the first noncascaded intersubband injection lasers based on a single optical transition is reported. The unipolar lasers are based on an active region consisting of three InGaAs quantum wells closely coupled by thin AlInAs barriers. The lasers emit at λ ≈ 7.7 μm wavelength and operate in pulsed mode up to 110 K. Peak power levels of 20 mW at 10 K and 4 mW at 110 K are obtained. The low-temperature threshold current density is 25.6 kA cm−2 in good agreement with calculations. Several advantages arise from this novel type of intersubband laser. First, only few layers are necessary to build the active region, simplifying sample preparation. Second, low operating voltages can be achieved, which is essential for many applications. Finally, the noncascaded intersubband laser allows studying fundamental properties of quantum cascade lasers without possible artifacts introduced by the sequential stacking of many active regions. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Above-room-temperature optically pumped midinfrared W lasers

W. W. Bewley, C. L. Felix, E. H. Aifer, I. Vurgaftman, L. J. Olafsen, J. R. Meyer, H. Lee, R. U. Martinelli, J. C. Connolly, A. R. Sugg, G. H. Olsen, M. J. Yang, B. R. Bennett, and B. V. Shanabrook

Appl. Phys. Lett. 73, 3833 (1998); http://dx.doi.org/10.1063/1.122909 (3 pages) | Cited 43 times

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We report temperature-dependent pulsed lasing performance, internal losses, and Auger coefficients for optically pumped type-II W lasers with wavelengths in the range of 3.08–4.03 μm at room temperature. All lased to at least 360 K, and produced 1.5–5 W peak power at 300 K. Internal losses at 100 K were as low as 10 cm−1, but increased to 90–360 cm−1 at 300 K. Room temperature Auger coefficients varied from 5×10−28 cm6/s at the shortest wavelength to 3×10−27 cm6/s at the longest. © 1998 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.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
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Neutral higher silane molecules in silane plasmas

Atsushi Suzuki

Appl. Phys. Lett. 73, 3836 (1998); http://dx.doi.org/10.1063/1.122897 (3 pages) | Cited 1 time

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Neutral higher silane molecules in silane radio frequency glow discharge plasmas are investigated using photoionization mass spectroscopy at various radio frequency (rf) powers and total pressures. Densities of higher silane molecules increase with rf power up to 10 W, and then decrease at 10–100 W. The reduction of the neutral higher silane molecules at high rf power suggests that these molecules contribute to the particle formation through secondary reactions in the plasma. © 1998 American Institute of Physics.
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52.80.Hc Glow; corona
52.80.Pi High-frequency and RF discharges
52.25.Ya Neutrals in plasmas
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Atomic structure and electronic properties of single-wall carbon nanotubes probed by scanning tunneling microscope at room temperature

A. Hassanien, M. Tokumoto, Y. Kumazawa, H. Kataura, Y. Maniwa, S. Suzuki, and Y. Achiba

Appl. Phys. Lett. 73, 3839 (1998); http://dx.doi.org/10.1063/1.122910 (3 pages) | Cited 44 times

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A detailed three-dimensional structural analysis of single-walled carbon nanotubes was carried out using a scanning tunneling microscope (STM) operated at room temperature in ambient conditions. On a microscopic scale, the images show tubes condensed in ropes as well as tubes which are separated from each other. For a single-wall nanotube rope, the outer portion is composed of highly oriented nanotubes with nearly uniform diameter and chirality. On separated nanotubes, atomically resolved images show variable chirality ranges between 0°–30°, and variable diameter (1–3 nm), with no one type dominant. From STM and scanning tunneling spectroscopy measurements we confirmed the correlation between chirality and the electronic properties, namely the tuning from metallic to semiconducting. We also observed a rectifying behavior correlated with the chiral angle of 25°, an important observation for nanodevices application. © 1998 American Institute of Physics.
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71.20.Tx Fullerenes and related materials; intercalation compounds
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
72.80.Rj Fullerenes and related materials

Load transfer in carbon nanotube epoxy composites

L. S. Schadler, S. C. Giannaris, and P. M. Ajayan

Appl. Phys. Lett. 73, 3842 (1998); http://dx.doi.org/10.1063/1.122911 (3 pages) | Cited 480 times

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The mechanical behavior of multiwalled carbon nanotube/epoxy composites was studied in both tension and compression. It was found that the compression modulus is higher than the tensile modulus, indicating that load transfer to the nanotubes in the composite is much higher in compression. In addition, it was found that the Raman peak position, indicating the strain in the carbon bonds under loading, shifts significantly under compression but not in tension. It is proposed that during load transfer to multiwalled nanotubes, only the outer layers are stressed in tension whereas all the layers respond in compression. © 1998 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
78.30.Na Fullerenes and related materials
61.41.+e Polymers, elastomers, and plastics
62.20.D- Elasticity

Growth of highly oriented carbon nanotubes by plasma-enhanced hot filament chemical vapor deposition

Z. P. Huang, J. W. Xu, Z. F. Ren, J. H. Wang, M. P. Siegal, and P. N. Provencio

Appl. Phys. Lett. 73, 3845 (1998); http://dx.doi.org/10.1063/1.122912 (3 pages) | Cited 109 times

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Highly oriented, multiwalled carbon nanotubes were grown on polished polycrystalline and single crystal nickel substrates by plasma enhanced hot filament chemical vapor deposition at temperatures below 666 °C. The carbon nanotubes range from 10 to 500 nm in diameter and 0.1 to 50 μm in length depending on growth conditions. Acetylene is used as the carbon source for the growth of the carbon nanotubes and ammonia is used for dilution gas and catalysis. The plasma intensity, acetylene to ammonia gas ratio, and their flow rates, etc. affect the diameters and uniformity of the carbon nanotubes. © 1998 American Institute of Physics.
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81.05.ub Fullerenes and related materials
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Effects of mechanical stress on electromigration-driven transgranular void dynamics in passivated metallic thin films

M. Rauf Gungor, Dimitrios Maroudas, and Leonard J. Gray

Appl. Phys. Lett. 73, 3848 (1998); http://dx.doi.org/10.1063/1.122913 (3 pages) | Cited 21 times

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The combined effects of mechanical stress and surface electromigration on the dynamics of transgranular voids in passivated metallic thin films are analyzed based on self-consistent dynamical simulations. Depending on the strength of the electric and stress fields, void morphological instabilities can lead to film failure by propagation from the void surface of either faceted slits or finer-scale crack-like features. Most importantly, there exists a narrow range of applied stress for given strength of electric field over which slit formation can be inhibited completely. © 1998 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.65.Rv Passivation
81.05.Bx Metals, semimetals, and alloys

Piezoelectric measurements with atomic force microscopy

J. A. Christman, R. R. Woolcott, A. I. Kingon, and R. J. Nemanich

Appl. Phys. Lett. 73, 3851 (1998); http://dx.doi.org/10.1063/1.122914 (3 pages) | Cited 95 times

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An atomic force microscope (AFM) is used to measure the magnitude of the effective longitudinal piezoelectric constant (d33) of thin films. Measurements are performed with a conducting diamond AFM tip in contact with a top electrode. The interaction between the tip and electric field present is a potentially large source of error that is eliminated through the use of this configuration and the conducting diamond tips. Measurements yielded reasonable piezoelectric constants of X-cut single-crystal quartz, thin film ZnO, and nonpiezoelectric SiO2 thin films. © 1998 American Institute of Physics.
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77.65.Bn Piezoelectric and electrostrictive constants
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
07.79.Lh Atomic force microscopes
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films

Electric circuit model for MgO-doped ZrO2–TiO2 ceramic humidity sensor

M. K. Jain, M. C. Bhatnagar, and G. L. Sharma

Appl. Phys. Lett. 73, 3854 (1998); http://dx.doi.org/10.1063/1.122915 (3 pages) | Cited 10 times

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The MgO-doped ZrO2–TiO2 ceramic pellets were studied for its humidity-sensitive electrical conduction. An equivalent circuit model has been proposed to define the humidity-sensitive electrical properties. This model is in agreement with the experimental findings. The electrical conduction is largely controlled by the intergranular impedance except at very high humidities. The impedance of the pellets showed inductive behavior in high-humidity region. This behavior can be attributed to the spherical paths adopted by charge carrier because conduction is mainly through the spherical grain surface. © 1998 American Institute of Physics.
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07.07.Vx Hygrometers; hygrometry
72.80.Ga Transition-metal compounds
72.20.Fr Low-field transport and mobility; piezoresistance
85.30.De Semiconductor-device characterization, design, and modeling

In situ reflectance difference spectroscopy of N-plasma doped ZnTe grown by molecular beam epitaxy

D. Stifter, M. Schmid, K. Hingerl, A. Bonanni, M. Garcia-Rocha, and H. Sitter

Appl. Phys. Lett. 73, 3857 (1998); http://dx.doi.org/10.1063/1.122916 (3 pages) | Cited 11 times

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In situ reflectance difference spectroscopy (RDS) has been performed during growth and nitrogen-doping of ZnTe thin films fabricated by molecular beam epitaxy. The doping level of the ZnTe samples can be determined by evaluating the RD spectra in the vicinity of the E1 and E1+Δ1 transitions. RDS features in this spectral range were used to optimize online the doping performance of the N-plasma cell. Furthermore, doping-induced surface processes have been investigated, like surface saturation with activated N species and surface Fermi level pinning occurring at ambient pressure. © 1998 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.40.Fy Semiconductors
61.72.uj III-V and II-VI semiconductors
81.05.Dz II-VI semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.20.At Surface states, band structure, electron density of states

Molecular dynamics-based ion-surface interaction models for ionized physical vapor deposition feature scale simulations

Daniel G. Coronell, David E. Hansen, Arthur F. Voter, Chun-Li Liu, Xiang-Yang Liu, and Joel D. Kress

Appl. Phys. Lett. 73, 3860 (1998); http://dx.doi.org/10.1063/1.122917 (3 pages) | Cited 22 times

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A procedure is presented for incorporating the results of atomistic simulations of ion–surface interactions into integrated circuit topographic simulations of ionized physical vapor deposition (PVD). Energy and angular dependent sticking probabilities for energetic Cu atoms impacting a {111} Cu surface, obtained from molecular dynamics simulations, were implemented in a simple Monte Carlo flux model. The resulting flux-averaged Cu sticking probability was found to vary significantly with position within submicron features and with the feature geometry. This illustrates the shortcomings of a constant (energy and angle independent) sticking probability model for ionized PVD. © 1998 American Institute of Physics.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Effect of the linewidth reduction on the characteristic time spread in C49–C54 phase transition

S. Privitera, F. La Via, M. G. Grimaldi, and E. Rimini

Appl. Phys. Lett. 73, 3863 (1998); http://dx.doi.org/10.1063/1.122918 (3 pages) | Cited 11 times

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The kinetics of the C49–C54 phase transformation in TiSi2 narrow strips for width in the 0.5–1.3 μm range was investigated by sheet resistance measurements. The experimental data follow the Johnson–Mehl–Avrami equation for the fraction of the transformed material, with an exponent equal to 1 for all of the analyzed linewidths. Nucleation sites saturation occurs and the growth is one-dimensional along the length of the strip. The characteristic time, as obtained by the fit, increases as 1/W, W being the width of the strip, and a nucleation density of about 0.05 sites/μm2 has been obtained. The distribution of the characteristic times around the average value increases with decreasing the linewidth. The amplitude of the dispersion is in quantitative agreement with the statistical fluctuation of the number of nucleation sites. © 1998 American Institute of Physics.
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64.70.K- Solid-solid transitions
73.61.At Metal and metallic alloys
61.72.Cc Kinetics of defect formation and annealing
64.60.Q- Nucleation

Observation of incident angle dependent phonon absorption in hydrogenated amorphous silicon nitride thin films

Tong Li and Jerzy Kanicki

Appl. Phys. Lett. 73, 3866 (1998); http://dx.doi.org/10.1063/1.122919 (3 pages) | Cited 3 times

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We have demonstrated the existence of longitudinal- and transverse-like optical modes of Si–N bond in vibrational absorption spectrum of hydrogenated amorphous silicon nitride thin films. One of the longitudinal-like optical resonances coincides with the transverse-like mode of Si–O bond, and the other closely neighbors the bending mode of N–H bond. We have also shown that the conventionally assigned asymmetric stretching mode of Si–N bond is merely a transverse-like mode of the bond. The microstructures of both longitudinal- and transverse-like modes can well be apprehended by a p-polarized beam at an oblique incidence light, especially at Brewster angle incidence. The spectrum distortion induced by interference fringes can be eliminated at this condition. © 1998 American Institute of Physics.
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78.66.Nk Insulators
78.35.+c Brillouin and Rayleigh scattering; other light scattering
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Structural characterization of thin GaN epilayers directly grown on on-axis 6H–SiC(0001) by plasma-assisted molecular beam epitaxy

B. Yang, A. Trampert, B. Jenichen, O. Brandt, and K. H. Ploog

Appl. Phys. Lett. 73, 3869 (1998); http://dx.doi.org/10.1063/1.122920 (3 pages) | Cited 11 times

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The structural properties of a series of thin (0.2–0.6 μm) GaN epilayers directly grown on 6H–SiC(0001) by plasma-assisted molecular beam epitaxy are studied. X-ray reciprocal space maps of the GaN(0002) reflection reveal negligible inhomogeneous strain within the layer but a comparatively large orientational spread of the GaN c axis. X-ray rocking curve measurements show, however, that this mosaicity steadily decreases with film thickness. In fact, the density of threading defects detected by transmission electron microscopy is found to decrease drastically with the distance away from the GaN/SiC interface, finally reaching a value of less than 5×109 cm−2 at a layer thickness of 0.5 μm. The formation mechanisms of the threading dislocations in the GaN films are discussed in consideration of the specific GaN/SiC interface structure. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
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Terahertz pulse-induced switching of a quantum-well optical amplifier

S. Hughes and D. S. Citrin

Appl. Phys. Lett. 73, 3872 (1998); http://dx.doi.org/10.1063/1.122921 (3 pages) | Cited 1 time

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We demonstrate theoretically that an intense half-cycle terahertz pulse can be used conjunctively with a quantum-well optical amplifier to form the basis of an efficient ultrahigh-speed optical switch. Our procedure implies terahertz and subterahertz switching and recovery rates, respectively. Constraints and practicalities are discussed. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Activation studies of low-dose Si implants in gallium nitride

C. J. Eiting, P. A. Grudowski, R. D. Dupuis, H. Hsia, Z. Tang, D. Becher, H. Kuo, G. E. Stillman, and M. Feng

Appl. Phys. Lett. 73, 3875 (1998); http://dx.doi.org/10.1063/1.122922 (3 pages) | Cited 20 times

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The implantation of Si ions into undoped high-resistivity GaN films is of interest for the realization of high-performance digital and monolithic microwave integrated circuits. We report the effect of postimplant annealing conditions on the electrical, optical, and surface morphology of Si ion-implanted GaN films. We demonstrate high activation efficiencies for low-dose Si implants into unintentionally doped GaN/sapphire heteroepitaxial films. The Si ions were implanted through an epitaxial AlN cap layer at 100 keV and a dose ∼ 5×1014 cm−2. Samples were subsequently annealed in an open-tube furnace for various times and temperatures. The postanneal electrical activation is correlated with the surface morphology of the film after annealing. The samples annealed at 1150 °C in N2 for 5 min. exhibited a smooth surface morphology and a sheet electron concentration ns ∼ 6.8×1013 cm−2. © 1998 American Institute of Physics.
Show PACS
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
68.35.B- Structure of clean surfaces (and surface reconstruction)
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