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15 Sep 1981

Volume 39, Issue 6, pp. 463-514


Subpicosecond pulse generation in a traveling‐wave ring laser using a synchronous double‐modulation scheme

J.‐M. Halbout, A. Olsson, and C. L. Tang

Appl. Phys. Lett. 39, 463 (1981); http://dx.doi.org/10.1063/1.92774 (3 pages) | Cited 2 times

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A new scheme for achieving traveling‐wave operation in synchronously mode‐locked ring lasers is demonstrated. The use of a very low dispersion electro‐optic modulator yielded subpicosecond optical pulses with autocorrelation full‐width at half‐maximum (FWHM) as short as 0.7 ps and with wide tunability.
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42.60.Fc Modulation, tuning, and mode locking
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Hp Optical processors, correlators, and modulators

Phase‐matched sum‐frequency light generation in optical fibers

Y. Sasaki and Y. Ohmori

Appl. Phys. Lett. 39, 466 (1981); http://dx.doi.org/10.1063/1.92775 (3 pages) | Cited 54 times

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The generation of phase‐matched two‐wave sum‐frequency light is observed in optical fibers. A Q‐switched and mode‐locked Nd:YAG laser is used as a pump laser. The two‐wave sum‐frequency light is generated from the pump and the first two Roman Stokes lines. Phase matching is achieved by using the dispersion of the waveguide modes to compensate for bulk dispersion. Conversion efficiencies of 1.1×10−3 and 0.5×10−3 from the pump into the two‐wave sum‐frequencies, whose peak wavelengths are 0.54 and 0.56 μm, respectively, are obtained with an 0.8‐kW peak pump power at 1.064 μm.
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42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.-k Nonlinear optics
42.81.-i Fiber optics
42.60.By Design of specific laser systems

Temperature dependence of optical gain spectra in GaInAsP/InP double‐heterostructure lasers

H. Jung, E. Göbel, K. M. Romanek, and M. H. Pilkuhn

Appl. Phys. Lett. 39, 468 (1981); http://dx.doi.org/10.1063/1.92776 (3 pages) | Cited 9 times

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Optical gain spectra of GaInAsP/InP double heterostructures (DHs) have been recorded in the temperature range of 80–300 K. These data are compared with threshold currents of DHs injection lasers fabricated from the same wafers. An identical behavior of maximum optical gain and threshold current is observed, i.e., two T0 values (100 and 63 K) with a break‐point temperature of TB ≃260 K are found. Furthermore, characteristic changes of the optical gain spectrum are observed close to the break‐point temperature.
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42.55.Px Semiconductor lasers; laser diodes
85.60.Jb Light-emitting devices
78.40.Fy Semiconductors

Tunneling‐determined threshold current in Pb1−xSnxTe diode lasers

D. Eger, M. Oron, A. Zemel, and A. Zussman

Appl. Phys. Lett. 39, 471 (1981); http://dx.doi.org/10.1063/1.92777 (3 pages) | Cited 6 times

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The current transport mechanism in n+‐n‐p+ homostructure diode lasers of Pb1−xSnxTe prepared by liquid‐phase epitaxy was studied using measurements of the I‐V characteristics as a function of temperature. It is found that the lasing threshold is dominated by excess tunneling current and not by diffusion current as previously assumed. To the best of our knowledge this is the first attempt to study the diffusion component of the injected current which determines the population inversion, and hence the threshold current, by analyzing the I‐V characteristics. The results of this work raise some doubt about the validity of the existing theoretical calculations of the threshold current in lead‐salt diode lasers.
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42.55.Px Semiconductor lasers; laser diodes
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Optical pulse compression in a cholesteric liquid crystal

D. N. Ghosh Roy, D. V. G. L. Narasimha Rao, and H. Bronk

Appl. Phys. Lett. 39, 474 (1981); http://dx.doi.org/10.1063/1.92778 (2 pages) | Cited 2 times

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A 20‐ns laser pulse is compressed to nearly 2.5 ns in a 10‐cm‐long sample of liquid‐crystal cholesteryl oleate in the isotropic phase. Pulse compression in a length as short as only 5 cm has been observed. A semiquantitative explanation is given in terms of stimulated Brillouin scattering.
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42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.45.+h Stimulated emission
42.62.-b Laser applications

Sezawa to Rayleigh mode conversion in the ZnO‐on‐Si surface acoustic wave device configuration

M. R. Melloch, R. L. Gunshor, and R. F. Pierret

Appl. Phys. Lett. 39, 476 (1981); http://dx.doi.org/10.1063/1.92779 (2 pages) | Cited 2 times

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Conversion of Sezawa surface waves to Rayleigh surface waves by means of an aluminum grating in the metal‐ZnO‐SiO2‐Si surface acoustic wave structure is reported. This conversion must be taken into account in the design of grating structures in ZnO‐on‐Si devices, such as multistrip couplers, to avoid unwanted stop bands. The conversion also provides a new phenomenological basis for the construction of bandpass filters.
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43.35.Pt Surface waves in solids and liquids
68.35.Ja Surface and interface dynamics and vibrations
62.30.+d Mechanical and elastic waves; vibrations

A proposed design for multishell cryogenic laser fusion targets using superconducting levitation

David A. Glocker

Appl. Phys. Lett. 39, 478 (1981); http://dx.doi.org/10.1063/1.92780 (2 pages)

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A method is described for using the diamagnetism of superconductors to levitate a permanently magnetized fuel pellet within a spherical superconducting shell in a multishell cryogenic laser fusion target. A general expression is derived for the magnetic force on the fuel pellet as a function of its displacement from the center of the outer shell, and is used to calculate the equilibrium displacement due to gravity in a typical case. For a PtCo inner shell with a radius of 50 μm and a thickness of 1 μm, within a superconducting outer shell with a radius of 100 μm, the maximum displacement is 0.54 μm.
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85.25.-j Superconducting devices
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
28.52.-s Fusion reactors

Picosecond photoconductivity in germanium films

A. P. DeFonzo

Appl. Phys. Lett. 39, 480 (1981); http://dx.doi.org/10.1063/1.92766 (3 pages) | Cited 8 times

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A picosecond photoconductive detector based on a new photoconductive material, ρ‐Ge, is described. Photoconductivity measurements show relaxation times less than 50 ps and sensitivities greater than 0.1 mA/mW with 25‐μm electrode spacings. A comparison is made with similar devices through the introduction of a merit‐figure Fi, which we propose as being particularly suited to evaluating picosecond photodetectors. The device is capable of operation to wavelengths of 1.7 μm.
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72.40.+w Photoconduction and photovoltaic effects
73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors

678‐mV open‐circuit voltage silicon solar cells

A. W. Blakers and M. A. Green

Appl. Phys. Lett. 39, 483 (1981); http://dx.doi.org/10.1063/1.92767 (3 pages) | Cited 7 times

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A new high‐performance cell structure has been developed, combining the better features of metal insulator semiconductor and p‐n junction technologies. The metal‐insulator‐NP junction (MINP) cell technology described has an inherently superior performance to either of its constituent technologies, producing open‐circuit voltages up to 678 mV (AMO, 25 °C) for silicon cells. Analysis of the dark saturation current of MINP devices as a function of bulk resistivity indicates that both bulk and surface recombination contribute to this current, with the former dominating. Prospects for exceeding 700‐mV open‐circuit voltage with this approach are discussed. The structure is particularly well suited for fabrication using ion implantation.
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84.60.Jt Photoelectric conversion
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.Hb Impurity and defect levels; energy states of adsorbed species

The effect of As/Ga flux ratio on the photoluminescent spectra from molecular beam epitaxially‐grown Sn‐doped AlxGa1−xAs

W. T. Tsang and V. Swaminathan

Appl. Phys. Lett. 39, 486 (1981); http://dx.doi.org/10.1063/1.92768 (2 pages) | Cited 27 times

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It is shown that the As/Ga flux ratio γf during molecular beam epitaxial growth has significant effects on the photoluminescent (PL) spectra at 5.5 K from a Sn‐doped AlxGa1−x As (x∼0.27–0.33) layer. At any growth temperature Ts samples grown under low γf have higher PL intensity than those grown under high γf . Based on the 5.5‐K PL spectra we arrive at the important conclusion that the highest‐quality AlxGa1−xAs is grown under conditions of high Ts and low γf , followed by layers grown at high Ts and high γf, and at low Ts and low γf , with the poorest‐quality layers grown under conditions of low Ts and high γf. The present results are consistent with the fact that low‐threshold double‐heterostructure lasers are obtained only when Ts is high.
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78.40.Fy Semiconductors
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

A comparison between selenium mass‐transported and selenium‐diffused silicon

B. Skarstam and J. Lennart Lindström

Appl. Phys. Lett. 39, 488 (1981); http://dx.doi.org/10.1063/1.92769 (3 pages) | Cited 5 times

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The appearance of the same excited‐state ladder for the shallow center in selenium‐doped and selenium mass‐transported silicon is confirmed for the first time. The lifting of the effective‐mass degenerate state in the two systems is seen in infrared absorption spectra as a peak at 2196 cm−1. The strength of this line is of the same order as that for the 2p0 line. The 3p± and higher excited states, in the mass‐transported sample are obscured by line broadening mechanisms. This is believed to be due to the incorporation mechanism of the selenium atoms during crystal growth and their concentration. In both systems an additional line is resolved at Ec −9.3 meV, which is close to the theoretical value for the 2s excited states for group V donors. As for the strength of the 1s(A1)–1s(T2) line (at 2196 cm−1), the strength of this line is believed to reflect the chemical nature of the selenium‐related optical defect center investigated.
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78.40.Fy Semiconductors
78.30.-j Infrared and Raman spectra
66.30.J- Diffusion of impurities
81.10.Fq Growth from melts; zone melting and refining

Hydrogen effusion under 6–7‐MeV 15N ions irradiation in oxygen‐contaminated thin films of sputtered a‐Si:H

M. Fallavier, J. P. Thomas, J. Tousset, Y. Monteil, and J. Bouix

Appl. Phys. Lett. 39, 490 (1981); http://dx.doi.org/10.1063/1.92770 (3 pages) | Cited 4 times

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We report on the modification of rf‐sputtered a‐Si:H thin films induced by high‐energy ion bombardment and which occurs during hydrogen analysis using the 1H(15N, αγ) 12C nuclear reaction. We find that hydrogen losses under ion bombardment occur for films containing oxygen impurities and that they are directly related to the oxygen contents. We show from infrared transmission measurements that the lost H comes from the dissociation of the Si–H bond in (SiH2)n and O–Si–H complexes induced by ionization processes along the ion trajectory in the film. These observations are a strong indication of the inhomogeneous structure of the O‐containing material.
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61.80.Jh Ion radiation effects
73.40.Ns Metal-nonmetal contacts
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
66.30.J- Diffusion of impurities

Backside‐gated modulation‐doped GaAs‐(AlGa)As heterojunction interface

H. L. Störmer, A. C. Gossard, and W. Wiegmann

Appl. Phys. Lett. 39, 493 (1981); http://dx.doi.org/10.1063/1.92771 (3 pages) | Cited 29 times

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We present a new kind of gated modulation‐doped GaAs‐(AlGa)As heterojunction interface. The gate voltage is applied from the backside of the specimen. Gate voltage dependences of the two‐dimensional electron concentration and its mobility μ are determined. The density variation is strictly linear in gate voltage, and the mobility follows approximately a law μ∝n5/2 over the explored region. This concept is similar to a junction field‐effect transistor but with a two‐dimensional channel. Forward bias improves the mobility by ≊50% to ≊120 000 (cm2/V sec).
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85.30.Tv Field effect devices

Electroreflectance and photoluminescence studies of InP epitaxial layers highly doped with selenium

P. M. Raccah, H. Rahemi, J. Zehnder, F. Z. Hawrylo, H. Kressel, and J. S. Helman

Appl. Phys. Lett. 39, 496 (1981); http://dx.doi.org/10.1063/1.92772 (3 pages) | Cited 8 times

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InP epi‐layers heavily doped with Se exhibit very high carrier concentrations (N≳1020 cm−3) together with significant increases of the optical band‐gap energy. We show that in these epi‐layers (grown by liquid phase epitaxy) the Se concentration XSe varies with the depth. With increasing Se concentration, the optical band gap increases from 1.34 to ∼1.9 eV, where it remains fixed for Se concentrations larger than 1.5 at.%. This increase is very rapid at first owing to the filling of the low mass conduction band. Beyond XSe = 0.1 at.%, we enter the nonarapbolic bands regime and the electrons begin to overflow into the indirect minima. Because of the large density of states available, further increases in free carriers no longer affect the optical gap, which remains close to the indirect gap value (∼1.9 eV).
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78.20.Jq Electro-optical effects
78.40.Fy Semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

The use of beam shaping to achieve large‐grain cw laser‐recrystallized polysilicon on amorphous substrates

T. J. Stultz and J. F. Gibbons

Appl. Phys. Lett. 39, 498 (1981); http://dx.doi.org/10.1063/1.92773 (3 pages) | Cited 43 times

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Laser beam shaping has been used to increase the grain size of laser‐recrystallized polycrystalline silicon on amorphous substrates. Using a slanted liquid‐solid interface, rectangular grains as large as 45×50 μm have been grown in 0.5‐μm‐thick chemical vapor deposited polysilicon on quartz substrates. Improved surface smoothness of recrystallized material has also been achieved using this procedure.
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81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)

Annealing and anomalous high‐energy electron irradiation effects in low‐cost silicon N+P solar cells

G. F. J. Garlick and A. H. Kachare

Appl. Phys. Lett. 39, 501 (1981); http://dx.doi.org/10.1063/1.92781 (3 pages) | Cited 1 time

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Silicon solar cells of N+P type made from multiple ingots grown from a single crucible were either subjected to 1‐MeV electron irradiation (fluence up to 1016 electrons/cm2) and then annealed at 450 °C for 20 min or to the annealing alone with no electron irradiation. Electron irradiation gave the expected degradation of longer‐wavelength cell response but at shorter wavelengths produced a marked enhancement of response with peak change of some 40% at 0.44 μm. Subsequent thermal anneal at 450 °C reduced the long‐wavelength degradation, but the enhancement at shorter wavelengths persisted. Excitation at the shorter wavelength is predominantly in the N+‐diffused layer and to some extent in the junction region of the cell. Anneal of unirradiated cells at 450 °C also produced the shorter‐wavelength enhancement at about half of that due to electron irradiation and more enhancement into the longer wavelength region (up to 0.8 μm), finally giving a small degradation. These effects in the different cell regions are attributed to a decrease in interstitial oxygen‐impurity complexes which act as deep recombination levels and the formation of substitutional oxygen‐silicon vacancy centers which act as donors. The investigations indicate that thermal regimes during cell processing can produce cell spectral characteristics that might be further improved by modification of such regimes.
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72.40.+w Photoconduction and photovoltaic effects
72.80.Cw Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
84.60.Jt Photoelectric conversion

A subharmonic Josephson relaxation oscillator—amplification and locking

N. Calander, T. Claeson, and S. Rudner

Appl. Phys. Lett. 39, 504 (1981); http://dx.doi.org/10.1063/1.92782 (3 pages) | Cited 11 times

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The inductance of the shunt loop in a resistively shunted Josephson tunnel junction may cause relaxation oscillations at subharmonics of the Josephson frequency. The relaxation period, the injection locking to a subharmonic of a strong external signal, and the amplification of weak signals were studied in detail. Gains up to 15 dB were achieved, but the noise temperature, which depended upon the harmonic of the relaxation frequency at which the amplification occurred, was high.
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74.50.+r Tunneling phenomena; Josephson effects
85.25.-j Superconducting devices

Radiative cooling with selectively emitting ethylene gas

A. Hjortsberg and C. G. Granqvist

Appl. Phys. Lett. 39, 507 (1981); http://dx.doi.org/10.1063/1.92783 (3 pages) | Cited 4 times

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We discuss passive cooling of ethylene gas which radiates predominantly in the wavelength range for which the atmospheric counter radiation is low for dry air. The radiative properties of the gas were investigated by spectrophotometry, and the parameters relevant for efficient cooling were computed. Daytime cooling to a temperature ∼10 °C below that of the ambient was demonstrated with a simple device.
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51.30.+i Thermodynamic properties, equations of state

Real‐time tritium imaging

M. E. Malinowski

Appl. Phys. Lett. 39, 509 (1981); http://dx.doi.org/10.1063/1.92784 (3 pages) | Cited 6 times

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A real‐time image of a tritium‐containing titanium film has been made by detecting the secondary electrons produced by tritium β decay with a simple two‐element electrostatic lens and microchannel plate image intensifier. The obtained image indicates that a resolution of better than 100 μm is currently obtainable and suggests that image magnification to enhance resolution should be possible.
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79.20.Hx Electron impact: secondary emission
29.25.Rm Sources of radioactive nuclei
29.40.Gx Tracking and position-sensitive detectors

New model of electron free path in multiple layers for Monte Carlo simulation

Seiji Horiguchi, Masanori Suzuki, Toshio Kobayashi, Hideo Yoshino, and Yutaka Sakakibara

Appl. Phys. Lett. 39, 512 (1981); http://dx.doi.org/10.1063/1.92785 (3 pages) | Cited 22 times

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A new model of an electron free path in multiple layers is proposed for Monte Carlo simulation of electron trajectories. In this model, the free path is calculated taking into account not only the scattering probability in the layer involving the initial scattering point but also that in the layers along the scattering direction. The result, simulated with the new model, agrees with the experimental result much better than results obtained with conventional models for backscattered electron intensity. It is also suggested that the simulation accuracy for the electron beam lithography is improved using the new model.
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79.20.Kz Other electron-impact emission phenomena
85.40.Bh Computer-aided design of microcircuits; layout and modeling
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