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11 Oct 1993

Volume 63, Issue 15, pp. 2015-2154

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Optical gain anisotropy in serpentine superlattice nanowire‐array lasers

S. Y. Hu, M. S. Miller, D. B. Young, J. C. Yi, D. Leonard, A. C. Gossard, P. M. Petroff, L. A. Coldren, and N. Dagli

Appl. Phys. Lett. 63, 2015 (1993); http://dx.doi.org/10.1063/1.110629 (3 pages) | Cited 5 times

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We report optical gain measurement from a serpentine superlattice nanowire‐array laser sample, grown by molecular beam epitaxy on a 2°‐off (100)GaAs vicinal substrate. Gain spectra, obtained from in‐plane ridge‐waveguide lasers with stripes either parallel or perpendicular to the nanowire arrays at 1.4 K, showed that the optical gain for the TM mode became greater than that of the TE mode when the optical cavity was placed along the nanowire direction. This provides strong evidence that the lateral quantum confinement in the serpentine superlattice is stronger than the vertical quantum confinement.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors

Nonlinear optical side‐chain polymer with high thermal stability and its pyroelectric thermal analysis

S. Bauer, W. Ren, Ş. Yilmaz, W. Wirges, W.‐D. Molzow, R. Gerhard‐Multhaupt, U. Oertel, B. Hänel, L. Häussler, H. Komber, and K. Lunkwitz

Appl. Phys. Lett. 63, 2018 (1993); http://dx.doi.org/10.1063/1.110630 (3 pages) | Cited 13 times

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Stable polymers with nonlinear optical side groups were synthesized from maleic anhydride copolymers and the azo dye Disperse Red 1 via esterification. After electrode poling under 135 V/μm at 185 °C, thermal stabilities were measured by pyroelectric and electro‐optic thermal analysis and compared to a guest/host polymer of polymethylmethacrylate and the same dye. The pyroelectrically detected dipole orientation and the electro‐optic activity of the side‐chain polymers decreased only above 150 °C, and electro‐optic r33 coefficients of up to 6 pm/V were achieved at 780 nm even without optimizing the dye content.
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42.70.Jk Polymers and organics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.66.Qn Polymers; organic compounds
77.70.+a Pyroelectric and electrocaloric effects

Pulse buildup in passively mode‐locked monolithic quantum‐well semiconductor lasers

Olav Solgaard, Meng‐Hsiung Kiang, and Kam Y. Lau

Appl. Phys. Lett. 63, 2021 (1993); http://dx.doi.org/10.1063/1.110631 (3 pages) | Cited 4 times

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The buildup of pulses in a passively mode‐locked monolithic semiconductor laser is investigated experimentally and theoretically. A simple model, based on competition between the fundamental and higher order mode‐locking ‘‘supermodes,’’ gives a time constant for the buildup in good agreement with the experimental values, which are on the order of 3.5 ns. The theory shows that to minimize the pulse buildup time, the photon life time and the width of the gain spectrum should be minimized, and the gain and the gain modulation, should be maximized.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Theoretical optimization of quantum wire array lasers for low threshold current density and high modulation frequency

Igor Vurgaftman and Jasprit Singh

Appl. Phys. Lett. 63, 2024 (1993); http://dx.doi.org/10.1063/1.110605 (3 pages) | Cited 1 time

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We show that as one decreases the cross‐sectional area of quantum wire lasers, the threshold current decreases, but the carrier relaxation time increases. Since the electron relaxation time sets the upper limit on the modulation frequency, there is a tradeoff between speed and efficiency in quantum wire lasers. We derive the optimal wire cross‐sectional area for a one‐dimensional array of quantum wire lasers based on a balance between an acceptably high maximum modulation frequency and a desirably low threshold current density. We find that for a relaxation time of 60 ps, the quantum wire of 150×150 Å cross section has the lowest threshold current density of 560 A/cm2. If high‐speed operation is not needed, the optimal choice for the quantum wire cross‐sectional area is 100×50 Å with the threshold current density of 420 A/cm2. For optimized quantum wells with the same cavity losses, the threshold current density is ≊620 A/cm2. We also present the results for the threshold current density and the relaxation time that allow one to find the optimal quantum wire structure weighing the speed and efficiency considerations in accordance with their relative importance.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Frequency and power stabilization of a three longitudinal mode He‐Ne laser using secondary beat frequency

H. S. Suh, T. H. Yoon, M. S. Chung, and O. S. Choi

Appl. Phys. Lett. 63, 2027 (1993); http://dx.doi.org/10.1063/1.110580 (3 pages) | Cited 13 times

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A method of frequency and power stabilization for an internal‐mirror He‐Ne laser using the secondary beat frequency between the three longitudinal modes is presented. Frequency and power fluctuation was ±1 MHz (2 parts in 109) and ±0.10% over 10 000 s, respectively. The square‐root Allan variance between the laser stabilized in this study and the iodine stabilized He‐Ne laser was 5×10−11 at average time of τ=1 s. Furthermore, we could obtain the output power of 2 mW in a single longitudinal mode.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Mi Dynamical laser instabilities; noisy laser behavior

Green up‐conversion laser emission in Er‐doped crystals at room temperature

R. Brede, E. Heumann, J. Koetke, T. Danger, G. Huber, and B. Chai

Appl. Phys. Lett. 63, 2030 (1993); http://dx.doi.org/10.1063/1.110581 (2 pages) | Cited 37 times

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We report room‐temperature pulsed up‐conversion laser oscillation in Er‐doped LiYF4 and KYF4 at 551 and 562 nm, respectively. In both crystals laser oscillation is observed on the 4S3/2‐4I15/2 ground state transition. Excitation was provided by a tunable flashlamp‐pumped Ti:sapphire laser in the spectral region around 810 nm. Additional pumping with a continuous wave krypton ion laser at 647 nm was beneficial to both lasers. Laser action has also been observed in Er‐doped Y3Al5O12 on the same transition.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.-v Laser optical systems: design and operation
42.70.Hj Laser materials

Control of emission characteristics in organic thin‐film electroluminescent diodes using an optical‐microcavity structure

Noriyuki Takada, Tetsuo Tsutsui, and Shogo Saito

Appl. Phys. Lett. 63, 2032 (1993); http://dx.doi.org/10.1063/1.110582 (3 pages) | Cited 117 times

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An electroluminescent diode with a microcavity structure which comprised a reflective Ag anode (36 nm), a hole transport dye layer (250 nm), an emission dye laser (15 nm), an electron transport dye layer (240 nm), and a reflective MgAg cathode was fabricated. A diode without the microcavity structure with a transparent ITO anode was also prepared for reference. The diode with microcavity was driven in the electric excitation mode and emission spectra at fixed detection angles were measured together with the angular dependence of emission intensity at fixed wavelengths. A sharpening of emission spectra and a marked alteration of emission patterns in the diode with microcavity were observed.
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78.60.Fi Electroluminescence
42.50.-p Quantum optics
85.60.Jb Light-emitting devices

First operation of a photocathode radio frequency gun injector at high duty factor

D. H. Dowell, K. J. Davis, K. D. Friddell, E. L. Tyson, C. A. Lancaster, L. Milliman, R. E. Rodenburg, T. Aas, M. Bemes, S. Z. Bethel, P. E. Johnson, K. Murphy, C. Whelen, G. E. Busch, and D. K. Remelius

Appl. Phys. Lett. 63, 2035 (1993); http://dx.doi.org/10.1063/1.110583 (3 pages) | Cited 15 times

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Tests of the electron beam injector for the Boeing/Los Alamos Average Power Laser Experiment have demonstrated first time operation of a photocathode radio frequency gun accelerator at 25% duty factor, exceeding previous photocathode operating parameters by three orders of magnitude. The macropulse format was 30 Hz and 8.3 ms with a micropulse frequency of 27 MHz. Average beam currents of up to 32 mA have been accelerated to 5 MeV for an average beam power of 160 kW. The macropulse peak current was 128 mA. The 32 mA average beam current exceeds previous cathode performance by a factor of 1000. Emittance measurements demonstrate excellent electron beam quality.
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41.60.Cr Free-electron lasers
41.75.Fr Electron and positron beams
85.60.Ha Photomultipliers; phototubes and photocathodes

A comparison of photoinduced poling and thermal poling of azo‐dye‐doped polymer films for second order nonlinear optical applications

P. M. Blanchard and G. R. Mitchell

Appl. Phys. Lett. 63, 2038 (1993); http://dx.doi.org/10.1063/1.110584 (3 pages) | Cited 30 times

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Photoinduced poling (PIP) is a new technique which allows the room‐temperature preparation of guest/host polymer films exhibiting significant polar order for nonlinear optical applications. We report a comparison of this novel technique with the conventional electrode poling procedure performed at the glass transition temperature of the polymer using disperse red 1/poly(methylmethacrylate) films. In particular, in situ second harmonic generation measurements show that levels of polar order achieved using these two techniques are similar. In contrast, the stability of the polar order is reduced by up to 20 times in terms of the decay time constant in films prepared using PIP although the stability is very dependent upon the temperature at which the poling was performed.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Jk Polymers and organics

Surface acoustic wave and Bleustein–Gulyaev wave generation in KTiOPO4 crystals

David K. T. Chu and John D. Bierlein

Appl. Phys. Lett. 63, 2041 (1993); http://dx.doi.org/10.1063/1.110585 (3 pages) | Cited 3 times

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Surface acoustic waves (SAW) are observed in a z‐cut KTP plate. Measured frequency response for x‐propagation SAW waves indicates a SAW velocity of about 3940 m/s which agrees with theoretical calculations. The calculated electromechanical coupling coefficient (kSAW2) is about 1%. X‐propagation Bleustein–Gulyaev waves (BG) have also been observed in a y‐cut KTP plate. Center frequency of a delay line with uniform interdigitated transducers indicates that BG waves possess a velocity about 4256 m/s which is also in good agreement with theory. Using known bulk parameters, the calculated electromechanical coupling coefficient for this BG wave (kBG2) is ≊4%.
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43.35.Pt Surface waves in solids and liquids
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics

Time‐modulated electron cyclotron resonance plasma discharge for controlling generation of reactive species

Seiji Samukawa and Shuichi Furuoya

Appl. Phys. Lett. 63, 2044 (1993); http://dx.doi.org/10.1063/1.110586 (3 pages) | Cited 54 times

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This study examines modulated electron cyclotron resonance (ECR) plasma discharge occurring within a few tens of μs. It can control the generation of reactive species in plasmas. Reactive species are measured by an actinometric optical emission spectroscopy in the pulsed plasma. Good correlation is found between the density ratio of CF2 radicals and F atoms in the CHF3 plasma, and the combination of the pulse duration and pulse intervals. These characteristics are explained by the dependence of reactive species generation in ECR plasma on a time within a few tens of μs. This method provides for controlling the polymerization during SiO2 etching.
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52.80.-s Electric discharges
52.50.Gj Plasma heating by particle beams
85.40.Hp Lithography, masks and pattern transfer

Photoelastic AlGaAs/GaAs waveguide polarizer

L. S. Yu, Z. F. Guan, Q. Z. Liu, F. Deng, S. A. Pappert, P. K. L. Yu, S. S. Lau, L. T. Florez, and J. P. Harbison

Appl. Phys. Lett. 63, 2047 (1993); http://dx.doi.org/10.1063/1.110587 (3 pages) | Cited 3 times

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AlGaAs/GaAs double heterostructure transverse‐electric (TE) waveguide polarizers, 5 mm long, with extinction ratios exceeding 20 dB and excess losses of <1 dB have been fabricated using simple thin film technology. The single‐mode photoelastic waveguides were made by depositing either a thin Ni film (∼1000 Å) with a 5‐μm‐wide window stripe pattern followed by thermal annealing or a thin W film (∼900 Å) with a 5‐μm stripe pattern using rf sputtering with the substrate under negative dc bias. The polarization mode selection is caused by the stress‐induced birefrigence of the photoelastic waveguides. The change in dielectric constant due to stresses in the thin film structure was obtained from the experimental intensity output profile using an iterative calculation method. The tensile stress is 3×109 dyn/cm2 in the fully reacted Ni3GaAs stressor layer. The stress in the as‐sputtered W films was compressive and decreased from 1×1010 dyn/cm2 to 4×109 dyn/cm2 after annealing between 300 and 500 °C for 30 min.
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42.79.Ci Filters, zone plates, and polarizers
78.20.Fm Birefringence
42.79.Gn Optical waveguides and couplers

Colloid formation effects on depth profile of implanted Ag in SiO2 glass

Noriaki Matsunami and Hideo Hosono

Appl. Phys. Lett. 63, 2050 (1993); http://dx.doi.org/10.1063/1.110588 (3 pages) | Cited 36 times

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Ag+ ions of 150 keV were implanted into SiO2 glasses at room temperature to doses of 0.1–60×1016/cm2. Formation of Ag colloids in SiO2 glasses was observed by the cross‐sectional transmission electron microscopy and optical absorption spectra. An anticorrelation is found between the Ag colloid size and the width of the Ag depth profile measured by Rutherford backscattering spectrometry. At low dose, the size of Ag colloids is small (<10 nm in diameter) and the Ag depth profile is close to that of a simulation calculation. At increasing dose, small Ag colloids and/or Ag atoms aggregate to grow up to ∼40 nm and the width of the Ag depth profile is reduced to ∼50 nm, which is close to the above colloid size, indicating that the size of a Ag colloid particle controls the Ag depth profile. The size and shape of colloids are the keys which modify the optical properties by metallic ion implantation for applications such as optical isolators.
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61.80.Jh Ion radiation effects
81.05.Pj Glass-based composites, vitroceramics
42.70.Ce Glasses, quartz

Effects of grown‐in stress on the metastable solid solubility limits in Sb implanted Ge0.1Si0.9 alloys

Stella Q. Hong, Q. Z. Hong, and J. W. Mayer

Appl. Phys. Lett. 63, 2053 (1993); http://dx.doi.org/10.1063/1.110589 (3 pages) | Cited 9 times

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Solid phase epitaxy and metastable solubility limits of implanted Sb atoms have been investigated in stressed and stress‐relaxed Ge0.1Si0.9 thin films. For a 5×1015 cm−2 Sb implantation, complete recrystallization is achieved for both samples after a 60 min furnace annealing at 600 °C. In the case of stress‐relaxed alloy, 91% of the Sb atoms are located at the substitutional sites of the Ge‐Si matrix. For the stressed sample, however, only 60% of the Sb atoms occupy the substitutional sites of the matrix. A defect‐free regrown layer is observed for the relaxed sample, while twins are formed near the location of the Sb concentration peak in the stressed Ge‐Si. The maximum solid solubilities of Sb are estimated to be 1.6×1021 and 8×1020 cm−3 for the relaxed and the stressed Ge0.1Si0.9, respectively.
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81.15.Np Solid phase epitaxy; growth from solid phases
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.80.Jh Ion radiation effects
64.75.-g Phase equilibria

Influence of the oxygen stoichiometry on the structural and optical properties of reactively evaporated ZrOx films

M. Bellotto, A. Caridi, E. Cereda, G. Gabetta, M. Scagliotti, and G. M. Braga Marcazzan

Appl. Phys. Lett. 63, 2056 (1993); http://dx.doi.org/10.1063/1.110590 (3 pages) | Cited 12 times

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Thin ZrOx films are deposited by reactive electron beam evaporation of pure zirconium metal at different oxygen partial pressures. Stoichiometry, structural composition and optical properties of these films are studied. Results from x‐ray diffraction and ellipsometry show that the crystallographic phase composition and the optical properties of the films can be controlled by a proper choice of the oxygen partial pressure. In comparison with direct evaporation of ZrO2, the reactive evaporation of zirconium metal improves the homogeneity of the refractive index along the film thickness thanks to an increased homogeneity in the crystallographic phase composition.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.66.Nk Insulators
68.55.-a Thin film structure and morphology

Activation volume associated with the relaxation of the second order nonlinear optical susceptibility in a guest‐host polymer

Shane C. Brower and L. Michael Hayden

Appl. Phys. Lett. 63, 2059 (1993); http://dx.doi.org/10.1063/1.110591 (3 pages) | Cited 7 times

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The volume associated with the relaxation of the second order nonlinear optical susceptibility in a guest‐host polymer was determined by measuring the change in the rate of decay of the second harmonic signal from poled films as a function of hydrostatic pressure. The logarithm of the decay rates determined from Kohlrausch–Williams–Watt fits was found to vary linearly with pressure from 1–2100 atm. Above 2100 atm a saturation effect was observed. An activation volume of 86±2 cm3/mole, nearly equal to the size of one monomer unit, was found.
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42.65.-k Nonlinear optics
42.70.Jk Polymers and organics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Pulsed laser annealing of P‐implanted diamond

M. G. Allen, S. Prawer, D. N. Jamieson, and R. Kalish

Appl. Phys. Lett. 63, 2062 (1993); http://dx.doi.org/10.1063/1.110592 (3 pages) | Cited 13 times

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Diamond deeply implanted with 4 MeV P ions to a dose of 1×1015/cm2 is annealed by a focused pulsed laser that is selectively absorbed by the implanted damaged layer. Laser treatment with multiple pulses at ever increasing power leads to excellent regrowth as measured by channeling Rutherford backscattering spectroscopy, surface profilometry, and by optical transmission. The importance of the deep implantation and the potential of this method for doping diamond is demonstrated.
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61.72.up Other materials
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing

Single‐domain surface layers formed by heat treatment of proton‐exchanged multidomain LiTaO3 crystals

Kiyoshi Nakamura and Ailie Tourlog

Appl. Phys. Lett. 63, 2065 (1993); http://dx.doi.org/10.1063/1.110593 (2 pages) | Cited 11 times

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A space charge field model to explain the mechanism of a ferroelectric domain inversion phenomenon in proton‐exchanged LiTaO3 has been proposed. This model predicts that single‐domain layers could be formed on both surfaces of a proton‐exchanged multidomain LiTaO3 plate without application of external electric fields. Experimental results demonstrating this prediction are reported. It is shown that the single‐domain surface layers formed had spontaneous polarizations directed outward from the plate. This suggests the existence of a space charge field near the surfaces.  
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77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.-k Nonlinear optics

Suppression of threading dislocation generation in highly lattice mismatched heteroepitaxies by strained short‐period superlattices

T. Kawai, H. Yonezu, Y. Ogasawara, D. Saito, and K. Pak

Appl. Phys. Lett. 63, 2067 (1993); http://dx.doi.org/10.1063/1.110594 (3 pages) | Cited 8 times

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The threading dislocation density was remarkably reduced in highly lattice mismatched heteroepitaxies of the In0.5Ga0.5As/GaAs(001) and GaAs/GaP(001) systems. The two‐dimensional growth mode was obtained even after the lattice relaxation by applying the strained short‐period superlattices. The misfit dislocations aligned along the 〈110〉 direction were mainly generated at heterointerfaces. The misfit strain was relieved by the generation of the misfit dislocations in the absence of three‐dimensional island growth. It was found that the generation of threading dislocations is effectively suppressed by introducing strained short‐period superlattices at the initial growth stage of highly lattice mismatched heteroepitaxies.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Layer‐by‐layer growth of GaAs studied by glancing angle scattering of fast ions

Yoshikazu Fujii, Kazumasa Narumi, Kenji Kimura, Michi‐hiko Mannami, Toyoyuki Hashimoto, Kiyoshi Ogawa, Fumihiko Ohtani, Tamio Yoshida, and Masatoshi Asari

Appl. Phys. Lett. 63, 2070 (1993); http://dx.doi.org/10.1063/1.110595 (3 pages) | Cited 16 times

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Angular distribution of scattered ions at glancing angle incidence of 3 keV He ions on a (001) surface of GaAs is studied during its molecular beam epitaxial growth. We report observation of intensity oscillations of the scattered ions from the growing surface. The period of the oscillations corresponds to the growth time of one monomolecular layer. The oscillations of the intensity is due to the oscillatory change in surface step density during layer‐by‐layer growth of the surface. This observation is in agreement with the intensity oscillations of reflection high‐energy electron diffraction (RHEED) from epitaxially growing surface of GaAs.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Selective encapsulation of the carbides of yttrium and titanium into carbon nanoclusters

Supapan Seraphin, Dan Zhou, Jun Jiao, James C. Withers, and Raouf Loutfy

Appl. Phys. Lett. 63, 2073 (1993); http://dx.doi.org/10.1063/1.110596 (3 pages) | Cited 39 times

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Characterization of the arc‐discharge deposits at the cathode from anodes containing yttrium oxide and titanium by transmission electron microscopy and x‐ray diffraction shows different results with respect to an encapsulation of the metal carbides into carbon clusters. Yttrium carbide is encapsulated into carbon nanoclusters in a crystalline phase. The formation of titanium carbide, on the other hand, preempts the formation of the carbon—carbon bonds necessary to form the carbon cages, so that only titanium carbide clusters are observed. Thermodynamic data support the interpretation of the results.
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61.46.-w Structure of nanoscale materials
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
81.10.Bk Growth from vapor

Effective carrier mean‐free path in confined geometries

R. A. Richardson and Franco Nori

Appl. Phys. Lett. 63, 2076 (1993); http://dx.doi.org/10.1063/1.110597 (3 pages) | Cited 1 time

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The concept of exchange length is used to determine the effects of boundary scattering on transport in samples of circular and rectangular cross section. Analytical expressions are presented for an effective mean free path for transport in the axial direction. The relationship to the phonon thermal conductivity is discussed.
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72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Andreev reflection at superconducting contacts to GaAs/AlGaAs heterostructures

K.‐M. H. Lenssen, M. Matters, C. J. P. M. Harmans, J. E. Mooij, M. R. Leys, W. van der Vleuten, and J. H. Wolter

Appl. Phys. Lett. 63, 2079 (1993); http://dx.doi.org/10.1063/1.110598 (3 pages) | Cited 13 times

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Highly transmissive ohmic contacts to the two‐dimensional electron gas in GaAs/AlGaAs heterostructures have been made. For these contacts, which are of μm scale, a newly developed process of Ti/Sn evaporation and diffusion has been used. Devices consisting of these superconducting contacts combined with gate structures have shown clear evidence for the occurrence of Andreev reflection. Moreover a marked effect of the gate voltage on the dV/dI−V characteristics has been found, which proves that superconductivity has been induced into the semiconductor.  
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74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
74.50.+r Tunneling phenomena; Josephson effects

Refractive indices of ZnMgSSe alloys lattice matched to GaAs

M. Ukita, H. Okuyama, M. Ozawa, A. Ishibashi, K. Akimoto, and Y. Mori

Appl. Phys. Lett. 63, 2082 (1993); http://dx.doi.org/10.1063/1.110599 (3 pages) | Cited 14 times

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We have experimentally investigated refractive indices n of ZnxMg1−xSySe1−y, using the ellipsometry method and reflection‐spectrum measurement. The samples are epitaxial films of undoped ZnxMg1−xSySe1−y grown by molecular beam epitaxy on semi‐insulating GaAs substrates. The obtained dispersion relations of n in the transparent region are classified by the band‐gap energy Eg. We have found that the refractive index n of ZnxMg1−xSySe1−y decreases as Eg increases. These results will be available for the design of blue laser diodes containing ZnMgSSe.  
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Hj Laser materials
42.55.Px Semiconductor lasers; laser diodes
78.66.Hf II-VI semiconductors

Investigation of the recombination activity of misfit dislocations in Si/SiGe epilayers by cathodoluminescence imaging and the electron beam induced current technique

V. Higgs and M. Kittler

Appl. Phys. Lett. 63, 2085 (1993); http://dx.doi.org/10.1063/1.110600 (3 pages) | Cited 16 times

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Misfit dislocations in as‐grown and Ni‐contaminated Si/SiGe epilayers have been characterized by cathodoluminescence (CL) spectroscopy, cathodoluminescence imaging, and the electron beam induced current technique (EBIC). Dislocations in the as‐grown layers had no radiative recombination (D bands) and no detectable room temperature EBIC contrast. Following Ni contamination the D bands were observed and the EBIC contrast increased. CL dark line contrast is observed by monochromatic imaging of the Si substrate luminescence. The CL dark line contrast was observed from all the dislocations, whether contaminated or as grown. The CL dark line contrast and EBIC contrast show a 1:1 correspondence of the nonradiative recombination at the misfit dislocation and also a semiquantitative agreement with the variation in measured contrast of the individual dislocations.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.60.Hk Cathodoluminescence, ionoluminescence
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
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