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18 Dec 2000

Volume 77, Issue 25, pp. 4083-4226

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In-plane anisotropic lasing characteristics of (110)-oriented GaInAsP quantum-well lasers

Kunishige Oe, Raj Bhat, and Mineo Ueki

Appl. Phys. Lett. 77, 4083 (2000); http://dx.doi.org/10.1063/1.1335848 (3 pages) | Cited 2 times

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(110)-oriented GaInAsP quantum-well (QW) lasers have been fabricated to investigate growth direction effects of the QW structure on laser performance. Large in-plane anisotropic threshold current densities in the lasers were observed between the [001] and [1math0] cavity directions of the (110)-oriented QW structure lasers. This large anisotropy is able to be ascribed to a stronger oscillator strength for [110]-polarized light. Fairly low threshold current densities of less than 0.6 kA/cm2 were obtained for the lasers with cavities along [001] direction in spite of the lower reflectivity of the reactive ion etching etched mirror surface. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.65.Cf Surface cleaning, etching, patterning
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.66.Fd III-V semiconductors

Second harmonic generation in microcrystallite films of ultrasmall Si nanoparticles

M. H. Nayfeh, O. Akcakir, G. Belomoin, N. Barry, J. Therrien, and E. Gratton

Appl. Phys. Lett. 77, 4086 (2000); http://dx.doi.org/10.1063/1.1334945 (3 pages) | Cited 24 times

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We dispersed crystalline Si into a colloid of ultrasmall nano particles (∼1 nm), and reconstituted it into microcrystallites films on device-quality Si. The film is excited by near-infrared femtosecond two-photon process in the range 765–835 nm, with incident average power in the range 15–70 mW, focused to ∼1 μm. We have observed strong radiation at half the wavelength of the incident beam. The results are analyzed in terms of second-harmonic generation, a process that is not allowed in silicon due to the centrosymmetry. Ionic vibration of or/and excitonic self-trapping on novel radiative Si–Si dimer phase, found only in ultrasmall nanoparticles, are suggested as a basic mechanism for inducing anharmonicity that breaks the centrosymmetry. © 2000 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.55.Ap Elemental semiconductors
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Vs Fine-particle systems
63.20.Ry Anharmonic lattice modes
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Ultrafast all-optical switching in a silicon-based photonic crystal

Alain Haché and Martin Bourgeois

Appl. Phys. Lett. 77, 4089 (2000); http://dx.doi.org/10.1063/1.1332823 (3 pages) | Cited 83 times

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We study the effect of two-photon absorption and Kerr nonlinearity on the optical properties of a one-dimensional photonic crystal made with amorphous silicon and SiO2. A stop band appearing near 1.5 μm is monitored with a weak probe beam and modulated by changes in the refractive index caused by a pump pulse at 1.71 μm with 18 GW/cm2 peak intensity. Nonlinear optical characterization of the sample using Z-scan points out to two-photon absorption as the main contributor to free carrier excitation in silicon at that power level. Modulation in the transmittance near the band edge is found to be dominated by the optical Kerr effect within the pulse overlap (∼400 fs) whereas free carrier index changes are observed for 12 ps. © 2000 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Pc Optical bistability, multistability, and switching, including local field effects
78.66.Jg Amorphous semiconductors; glasses
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Db Elemental semiconductors and insulators

Photon scanning tunneling optical microscopy with a three-dimensional multiheight imaging mode

M. L. M. Balistreri, J. P. Korterik, L. Kuipers, and N. F. van Hulst

Appl. Phys. Lett. 77, 4092 (2000); http://dx.doi.org/10.1063/1.1335851 (3 pages) | Cited 7 times

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A photon scanning tunneling microscope with a three-dimensional multiheight mode has been developed for the mapping of optical field distributions in integrated optical waveguide structures. The optical field is measured at different heights above the waveguide surface. The multiheight measurements also contain the optical information gathered with the commonly used constant gap measurements in addition to the topography of the waveguide surface. With the multiheight method, the decay length of the evanescent field is readily determined as function of the in-plane coordinate. Moreover, the evanescent light can be distinguished from scattered light. © 2000 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes
07.79.-v Scanning probe microscopes and components
42.82.Et Waveguides, couplers, and arrays
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Many-body optical gain of (10math0) wurtzite GaN/AlGaN quantum-well lasers

Seoung-Hwan Park

Appl. Phys. Lett. 77, 4095 (2000); http://dx.doi.org/10.1063/1.1334911 (3 pages) | Cited 5 times

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Optical properties of (10math0)-oriented wurtzite (WZ) GaN/AlGaN quantum well (QW) lasers are investigated by the non-Markovian gain model with many-body effects. These results are compared with those of (0001)-oriented WZ GaN/AlGaN QW with spontaneous and piezoelectric polarization taken into account. The energy pattern of the (10math0) orientation shows two-fold symmetry while the energy pattern of the (0001) orientation is completely isotropic. It is found that the many-body effects are more dominant in the (0001)-oriented QW compared to the (10math0)-oriented QW. This is because the average hole effective mass of the (0001)-oriented QW is larger than that of the (10math0)-oriented QW. Thus, the flatband model shows that the optical gain of the (10math0)-oriented QW is smaller than that of the (0001)-oriented QW. However, with the inclusion of the internal fields, it is observed that the optical gain of the (0001)-oriented QW is significantly smaller than that of the (10math0)-oriented QW. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors

Adaptive interferometer using self-induced electro-optic modulation

Alexei A. Kamshilin, Kimmo Päiväsaari, Marvin Klein, and Bruno Pouet

Appl. Phys. Lett. 77, 4098 (2000); http://dx.doi.org/10.1063/1.1334944 (3 pages) | Cited 6 times

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We demonstrate the linear transformation of small phase excursions of a speckled wavefront into modulation of the transmitted intensity using the polarization self-modulation effect in photoconductive electro-optic crystals. The technique is more advantageous than the widely used photorefractive two-wave mixing technique. © 2000 American Institute of Physics.
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07.60.Ly Interferometers
42.30.Ms Speckle and moiré patterns
42.79.Hp Optical processors, correlators, and modulators
42.25.Ja Polarization

Study of gain mechanisms in AlGaN in the temperature range of 30–300 K

J. B. Lam, S. Bidnyk, G. H. Gainer, B. D. Little, J. J. Song, and W. Yang

Appl. Phys. Lett. 77, 4101 (2000); http://dx.doi.org/10.1063/1.1333692 (3 pages)

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We report the results of an experimental study of the stimulated emission (SE) properties of AlGaN epilayers grown by metalorganic chemical vapor deposition under high optical excitation conditions in the temperature range of 30–300 K. The band gap and energy position of spontaneous and SE peaks were measured over the entire temperature range studied. Through an analysis of the temperature dependence of the relative energy positions and the SE threshold, combined with absorption and time-resolved photoluminescence measurements, we estimated the carrier density at threshold to be ∼ 1019 cm−3 throughout the temperature range studied. Such a high carrier density indicates that an electron-hole plasma is responsible for the generation of gain in this material system from 30 to 300 K. Issues related to the development of short-wavelength AlGaN-based light emitting devices are discussed. © 2000 American Institute of Physics.
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78.45.+h Stimulated emission
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
73.61.Ey III-V semiconductors
73.50.Mx High-frequency effects; plasma effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Detection of up to 20 THz with a low-temperature-grown GaAs photoconductive antenna gated with 15 fs light pulses

Shunsuke Kono, Masahiko Tani, Ping Gu, and Kiyomi Sakai

Appl. Phys. Lett. 77, 4104 (2000); http://dx.doi.org/10.1063/1.1333403 (3 pages) | Cited 41 times

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We report on the ultrabroadband coherent detection of radiation in wavelengths spanning from far to midinfrared with a low-temperature-grown GaAs photoconductive dipole antenna gated with 15 fs light pulses. The detected spectral frequency exceeds 20 THz. © 2000 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Distributed Bragg reflectors for visible range applications based on (Zn,Cd,Mg)Se lattice matched to InP

S. P. Guo, O. Maksimov, M. C. Tamargo, F. C. Peiris, and J. K. Furdyna

Appl. Phys. Lett. 77, 4107 (2000); http://dx.doi.org/10.1063/1.1334650 (3 pages) | Cited 6 times

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Lattice-matched (Zn,Cd,Mg)Se epilayers were grown by molecular-beam epitaxy on InP substrates. X-ray diffraction and photoluminescence measurements show the high crystalline quality of the epilayers. Using a prism coupler technique, the index of refraction of the epilayers was investigated at four discrete wavelengths. With these results, (Zn,Cd,Mg)Se-based distributed Bragg reflector structures have been grown, covering nearly the entire visible spectral range. A maximum reflectivity of 95% has been achieved for structures having 16 periods. © 2000 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
42.55.Px Semiconductor lasers; laser diodes
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.55.Et II-VI semiconductors

Angular distribution of x-ray emission from a copper target irradiated with a femtosecond laser

Yoichiro Hironaka, Kazutaka G. Nakamura, and Ken-ichi Kondo

Appl. Phys. Lett. 77, 4110 (2000); http://dx.doi.org/10.1063/1.1335841 (2 pages) | Cited 7 times

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Angular distribution of hard x rays that are generated by focusing a femtosecond (41 fs) laser with a power density of 1.3×1017 W/cm2 onto a copper target was studied. The total x rays over an energy range of 4–20 keV, which were mainly assigned to bremsstrahlung, showed forward emission particularly at s-polarized incidence and the characteristic x rays (Cu Kα emission) were almost isotropic. © 2000 American Institute of Physics.
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78.70.En X-ray emission spectra and fluorescence
61.82.Bg Metals and alloys
79.20.Ds Laser-beam impact phenomena
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Production and characterization of a fully ionized He plasma channel

E. W. Gaul, S. P. Le Blanc, A. R. Rundquist, R. Zgadzaj, H. Langhoff, and M. C. Downer

Appl. Phys. Lett. 77, 4112 (2000); http://dx.doi.org/10.1063/1.1329323 (3 pages) | Cited 49 times

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We report guiding of intense (I = 1.3±0.7×1017 W/cm2) 80 fs laser pulses with negligible spectral distortion through 1.5-cm-long preformed helium plasma channels. Channels were formed by axicon-focused laser pulses of either 0.3 J energy, 100 ps duration, after preionizing a 200–700 Torr backfill of He gas to ne ∼ 1016 cm−3 with a pulsed electrical discharge; or 0.6–1.1 J energy, 400 ps duration, which required neither preionization nor intentional impurities for seeding. Transverse interferometry showed that He was fully ionized on the channel axis in both cases. Identical femtosecond pulses suffered substantial ionization-induced blueshifts after propagating through Ar and Ne channels of similar dimensions. © 2000 American Institute of Physics.
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52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.38.-r Laser-plasma interactions
41.75.Jv Laser-driven acceleration

Ar2 excimer emission from a laser-heated plasma in a high-pressure argon gas

A. Takahashi, T. Okada, T. Hiyama, M. Maeda, K. Uchino, R. Nohdomi, and H. Mizoguchi

Appl. Phys. Lett. 77, 4115 (2000); http://dx.doi.org/10.1063/1.1334656 (3 pages)

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We investigated a pump scheme to establish a practical Ar2 excimer laser operating at 128 nm. In this scheme, electrons generated by preionization of Ar gas at high pressure were heated by intense pulsed CO2 laser radiation. The resultant high-density plasma in the high-pressure Ar gas was used to create excited Ar dimers. In the experiment, a CO2 laser beam from a transversely excited atmospheric CO2 laser was focused on a narrow line, 100 mm in length, in Ar gas at a pressure of 2 MPa. A vacuum ultraviolet (VUV) signal was observed only when the Ar was preionized, and the VUV signals were identified as the emission of Ar2 excimers from the features of the spectrum which was centered on 128 nm. © 2000 American Institute of Physics.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Kinetic of the NO removal by nonthermal plasma in N2/NO/C2H4 mixtures

F. Fresnet, G. Baravian, L. Magne, S. Pasquiers, C. Postel, V. Puech, and A. Rousseau

Appl. Phys. Lett. 77, 4118 (2000); http://dx.doi.org/10.1063/1.1332413 (3 pages) | Cited 29 times

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NO removal is studied in N2/NO and in N2/NO/C2H4 mixtures through time-resolved laser-induced fluorescence in the afterglow of a pulsed homogeneous discharge. NO density measurements are compared with predictions of a 0D model on a large range of parameter values, such as the specific deposited energy and the ethene initial concentration. It is shown that dissociation of NO through collision with the N2(a′1Σu−) state play the main part in the NO removal kinetic. Moreover, quenching of N2(a′1 Σu−) by C2H4 leads to a drastic decrease of the NO removal efficiency when ethene is added to N2/NO. The determined rate coefficient value for the quenching mechanism is (4±2)×10−10 cm3 s−1. © 2000 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
82.20.Pm Rate constants, reaction cross sections, and activation energies
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
52.80.Hc Glow; corona
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Critical layer thickness determination of GaN/InGaN/GaN double heterostructures

M. J. Reed, N. A. El-Masry, C. A. Parker, J. C. Roberts, and S. M. Bedair

Appl. Phys. Lett. 77, 4121 (2000); http://dx.doi.org/10.1063/1.1334361 (3 pages) | Cited 17 times

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We report on the critical layer thickness of GaN/InxGa1−xN/GaN double heterostructures in the composition range 0<x<0.16. The evolution of the photoluminescence spectra and the electrical properties of the InxGa1−xN well were monitored as its thickness was increased for a given % InN. Due to compressive stress and possible quantum-size effects, the emission energy from thin InGaN wells is blueshifted relative to thicker wells of a given % InN. The transition from the blueshifted emission of strained InGaN to redshifted emission of relaxed InGaN is also accompanied by dramatic changes in film conductivity and mobility. The thickness at which the onset of relaxation occurs is deemed the critical layer thickness of the InxGa1−xN film. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance

Planar degenerated anchoring of liquid crystals obtained by surface memory passivation

I. Dozov, D. N. Stoenescu, S. Lamarque-Forget, Ph. Martinot-Lagarde, and E. Polossat

Appl. Phys. Lett. 77, 4124 (2000); http://dx.doi.org/10.1063/1.1334909 (3 pages) | Cited 19 times

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Weak anchoring of liquid crystals on solid substrates is usually dominated by the surface memory. We show that the memory can be removed by surface passivation by silane molecules. We realize planar, azimuthally degenerated, and memory-free anchorings without pretilt. © 2000 American Institute of Physics.
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42.70.Df Liquid crystals
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures

Broad-area optical characterization of well-width homogeneity in GaN/AlxGa1−xN multiple quantum wells grown on sapphire wafers

A. Pomarico, M. Lomascolo, A. Passaseo, R. Cingolani, M. Berti, E. Napolitani, M. Natali, S. K. Sinha, and A. V. Drigo

Appl. Phys. Lett. 77, 4127 (2000); http://dx.doi.org/10.1063/1.1334358 (3 pages)

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We have performed spatially resolved photoluminescence spectroscopy on the entire 2 in. sapphire wafers containing GaN/AlxGa1−xN multiple quantum wells grown by metalorganic chemical vapor deposition. We have observed an energy shift of about 50 meV in the ground level emission energy between the center and the peripheric regions of the samples. We show that such a variation in the emission energy is due to a well narrowing of about 3 ML from the center to the outer regions of the wafers, which induces a large Stark shift through the built-in field. © 2000 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.20.Jq Electro-optical effects

C-MoS2 and C-WS2 nanocomposites

W. K. Hsu, Y. Q. Zhu, H. W. Kroto, D. R. M. Walton, R. Kamalakaran, and M. Terrones

Appl. Phys. Lett. 77, 4130 (2000); http://dx.doi.org/10.1063/1.1329326 (3 pages) | Cited 9 times

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Composite C-MoS2 and C-WS2 nanostructures were produced by pyrolysing H2S/N2 over a mixture of MoO3 (or WO3) and carbon particles/nanotubes. MoS2 particles embedded in the nanotubes were also observed occasionally. © 2000 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials
81.05.Cy Elemental semiconductors
81.05.ub Fullerenes and related materials
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Pressure effects on Al89La6Ni5 amorphous alloy crystallization

Y. X. Zhuang, J. Z. Jiang, T. J. Zhou, H. Rasmussen, L. Gerward, M. Mezouar, W. Crichton, and A. Inoue

Appl. Phys. Lett. 77, 4133 (2000); http://dx.doi.org/10.1063/1.1332409 (3 pages) | Cited 35 times

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The pressure effect on the crystallization of the Al89La6Ni5 amorphous alloy has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction using synchrotron radiation. The amorphous alloy crystallizes in two steps in the pressure range studied (0–4 GPa). The first process, corresponding to simultaneous precipitation of fcc-Al crystals and the metastable bcc-(AlNi)11La3-like phase, is governed by a eutectic reaction. The second process corresponds to the transformation of a residual amorphous alloy into fcc-Al, Al11La3, Al3Ni, and as yet unidentified phase(s). The applied pressure strongly affects the crystallization processes of the amorphous alloy. Both temperatures first decrease with pressure in the pressure range of 0–1 GPa and then increase with pressure up to 4 GPa. The results are discussed with reference to competing processes between the thermodynamic potential barrier and the diffusion activation energy under pressure. © 2000 American Institute of Physics.
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61.43.Fs Glasses
62.50.-p High-pressure effects in solids and liquids
81.05.Bx Metals, semimetals, and alloys
81.30.Mh Solid-phase precipitation
64.75.-g Phase equilibria
61.05.cp X-ray diffraction

Size-controlled short nanobells: Growth and formation mechanism

X. Ma, E. G. Wang, R. D. Tilley, D. A. Jefferson, and W. Zhou

Appl. Phys. Lett. 77, 4136 (2000); http://dx.doi.org/10.1063/1.1332407 (3 pages) | Cited 19 times

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Very short nanofibers containing only a few nanobells have been produced from nitrogen-doped carbon nanotubes by two methods, H2 plasma treatment, followed by grinding and oxidation with acidified potassium permanganate. The length of these short nanofibers can be controlled to give a wide range of sizes. The shortest nanofibers are composed of only a single nanobell with dimensions of ∼15 nm in diameter and length. High-resolution transmission electron microscope images reveal that their structures are closed at one end and open at the other. The formation mechanism of these short nanofibers and individual nanobells is discussed along with their potential for interesting nanotube-end physics and chemistry. © 2000 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Long-range ordered lines of self-assembled Ge islands on a flat Si (001) surface

O. G. Schmidt, N. Y. Jin-Phillipp, C. Lange, U. Denker, K. Eberl, R. Schreiner, H. Gräbeldinger, and H. Schweizer

Appl. Phys. Lett. 77, 4139 (2000); http://dx.doi.org/10.1063/1.1326842 (3 pages) | Cited 84 times

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Self-assembled growth in combination with prepatterning yields ordered lines of Ge islands on a planar Si (001) surface. The self-assembled Ge nanostructures are grown on top of a 15-period Si/SiGe superlattice, which is deposited on a prepatterned Si substrate. The pattern consists of 10 nm deep trenches with a period of 250 nm. The superlattice translates the surface modulation of the substrate into a strain-field modulation at the growth front of the superlattice. This strain field modulation provides the template for the ordered nucleation of self-assembled Ge islands. Our method gives rise to the long-range ordering of perfectly passivated nanostructures and can in principle be applied to any other strained material system. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.05.Cy Elemental semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
68.55.-a Thin film structure and morphology
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Intersubband transitions in bismuth nanowires

M. R. Black, M. Padi, S. B. Cronin, Y.-M. Lin, O. Rabin, T. McClure, G. Dresselhaus, P. L. Hagelstein, and M. S. Dresselhaus

Appl. Phys. Lett. 77, 4142 (2000); http://dx.doi.org/10.1063/1.1333402 (3 pages) | Cited 22 times

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Optical absorption associated with the one-dimensional joint density of states of an intersubband transition in bismuth nanowires is reported. The previously observed strong absorption in bismuth nanowires at ∼ 1000 cm−1 is here shown to depend on the wire diameter and on the polarization of the incident light. The absorption line shape, the decreasing frequency with increasing wire diameter, and the polarization dependence of the reflectivity, all indicate that this resonance is due to an intersubband absorption resulting from quantum-confinement effects. © 2000 American Institute of Physics.
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78.66.Bz Metals and metallic alloys
78.30.Er Solid metals and alloys

Spectroscopy of competing mechanisms generating stimulated emission in gallium nitride

W. D. Herzog, G. E. Bunea, M. S. Ünlü, B. B. Goldberg, and R. J. Molnar

Appl. Phys. Lett. 77, 4145 (2000); http://dx.doi.org/10.1063/1.1332818 (3 pages) | Cited 3 times

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Two competing recombination mechanisms of stimulated emission in the vicinity of 145 K have been directly observed in the temperature dependence of the optical emission spectra for high-quality, unintentionally doped gallium nitride. Our analysis of the spectra indicates that exciton-exciton scattering is responsible for stimulated emission below 145 K, while at higher temperatures an electron-hole plasma becomes the dominant mechanism. © 2000 American Institute of Physics.
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78.45.+h Stimulated emission
78.55.Cr III-V semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
71.35.Ee Electron-hole drops and electron-hole plasma

Influence of dual incorporation of In and N on the luminescence of GaInNAs/GaAs single quantum wells

B. Q. Sun, D. S. Jiang, Z. Pan, L. H. Li, and R. H. Wu

Appl. Phys. Lett. 77, 4148 (2000); http://dx.doi.org/10.1063/1.1334357 (3 pages) | Cited 18 times

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The optical properties of above- and below-band-edge transitions have been investigated by incorporating In atoms into GaNAs/GaAs single quantum wells. The experimental results show that with increasing In concentration the interband luminescence is improved and the luminescence intensity below the band edge in GaInNAs/GaAs decreases significantly. An interpretation is given that N atoms are preferable to form a covalent bond with In than with Ga atoms in a GaInNAs alloy, due to the compensation of the atomic-size difference between In and N atoms on the GaAs substrate. The photoreflectance spectra of the GaInNAs/GaAs single quantum well support the assignment of an intrinsic mechanism to the high-energy luminescence peak. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

Surface morphology of ion-beam-irradiated rutile single crystals

Manabu Ishimaru, Yoshihiko Hirotsu, Fuxin Li, and Kurt E. Sickafus

Appl. Phys. Lett. 77, 4151 (2000); http://dx.doi.org/10.1063/1.1335844 (3 pages) | Cited 1 time

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Ion-beam-induced structural changes in rutile (TiO2) have been examined in detail using transmission electron microscopy (TEM). Single crystals of rutile with (100) orientation were irradiated with 360 keV Xe ions at room temperature to a fluence of 4×1015/cm2. In addition to a buried damage layer induced by projectile ions, a damage layer was formed near the surface (thickness about 10 nm). Nanobeam electron diffraction measurements and high-resolution TEM observations revealed that the surface damage layer consists of rutile crystallites with different orientations compared to the original single crystal. We discuss damage recovery processes in ion irradiated rutile within the context of our results as well as previous observations. © 2000 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)

Observation of the crystal-field splitting related to the Mn-3d bands in spinel-LiMn2O4 films by optical absorption

K. Kushida and K. Kuriyama

Appl. Phys. Lett. 77, 4154 (2000); http://dx.doi.org/10.1063/1.1336552 (3 pages) | Cited 16 times

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Mn 3d bands in spinel-LiMn2O4 films, synthesized on SiO2-glass substrates by a sol-gel method, were studied using an optical absorption method. Two absorption peaks were observed at around 1.63 and 2.00 eV at room temperature. These peaks were associated with two d–d transitions: One is the Mn t2g to the lower Mn eg bands transition and the other the Mn t2g to the upper Mn eg bands one. A large absorption was also observed above 3.0 eV, indicating a transition from the O 2p valence band to the Mn 3d bands. The d–d transitions showed the blueshifts of 20–30 meV at 77 K comparing with those at room temperature. The observed electronic structure was consistent with the calculated one. © 2000 American Institute of Physics.
Show PACS
78.66.Li Other semiconductors
71.70.Ch Crystal and ligand fields
71.20.Nr Semiconductor compounds
78.40.Fy Semiconductors
78.30.Hv Other nonmetallic inorganics
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