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2 Mar 1998

Volume 72, Issue 9, pp. 1001-1123

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Low-threshold InAlGaAs vertical-cavity surface-emitting laser arrays using transparent contacts

C. L. Chua, R. L. Thornton, D. W. Treat, M. Kneissl, and C. Dunnrowicz

Appl. Phys. Lett. 72, 1001 (1998); http://dx.doi.org/10.1063/1.120947 (3 pages) | Cited 3 times

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We present top-emitting all-epitaxial planar laterally oxidized vertical-cavity surface-emitting lasers employing transparent indium–tin–oxide electrodes. The transparent contacts facilitate device fabrication and offer significantly denser device packing than similar planar laterally oxidized structures using metal contacts. The InAlGaAs-based devices operate at a wavelength of 817 nm with a minimum threshold current of 175 μA. © 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.By Design of specific laser systems

X-ray characterization of GaN/AlGaN multiple quantum wells for ultraviolet laser diodes

D. Korakakis, K. F. Ludwig, and T. D. Moustakas

Appl. Phys. Lett. 72, 1004 (1998); http://dx.doi.org/10.1063/1.120976 (3 pages) | Cited 10 times

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GaN/Al0.20Ga0.80N (50 Å/50 Å) multiple quantum wells (MQW) with 15 periods were grown on (0001) sapphire substrates by molecular beam epitaxy and evaluated by x-ray diffraction. To simulate an ultraviolet laser diode structure, the substrate was coated first with n-GaN as the bottom contact layer and n-Al0.25Ga0.75N as the corresponding cladding layer. The crystal structure of this system was investigated by studying the reciprocal lattice map of off-axis diffraction peaks as well as the θ–2θ pattern around the (0002) reflection. The MQW was found to be coherent and has the a-lattice parameter of the underlying Al0.25Ga0.75N. The good agreement between experimental and theoretical data in the relative intensity of up to third-order satellite peaks supports that the interfaces of the MQW are abrupt, and thus, interdiffusion of Ga and Al atoms at the growth temperature was negligible. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Efficient frequency doubling of 1.5 μm femtosecond laser pulses in quasi-phase-matched optical fibers

V. Pruneri, G. Bonfrate, P. G. Kazansky, C. Simonneau, P. Vidakovic, and J. A. Levenson

Appl. Phys. Lett. 72, 1007 (1998); http://dx.doi.org/10.1063/1.120948 (3 pages) | Cited 7 times

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Second-order nonlinear gratings in optical fibers have been produced for efficient quasi-phase-matched frequency conversion around 1.5 μm. Periodic poling was achieved by defining a patterned electrode on a D-shape fiber via standard lithography and applying high voltage (4–5 kV) at elevated temperature (270–280 °C). This fabrication technique has allowed us to produce gratings uniform over 7.5 cm, as indicated by the shape and the bandwidth of the phase-matching curve. By frequency doubling ∼100 fs pulses in a grating ∼4 cm long and with a period of 57.15 μm, ∼1.05 mW average power at 768 nm has been generated, with an average conversion efficiency ∼1.2%. © 1998 American Institute of Physics.
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42.81.Bm Fabrication, cladding, and splicing
42.81.Dp Propagation, scattering, and losses; solitons
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Dj Gratings

Heterostructure optoelectronic switch with lightcontrollable S-shaped negative differential resistance

Der-Feng Guo

Appl. Phys. Lett. 72, 1010 (1998); http://dx.doi.org/10.1063/1.120949 (3 pages) | Cited 3 times

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A heterostructure optoelectronic switch, grown by molecular beam epitaxy, has been fabricated. Owing to the carrier confinement and avalanche multiplication in the transport mechanism, S-shaped negative-differential-resistance performances are observed in the current–voltage (I–V) characteristics. The device shows a flexible optical function related to the potential barrier height and breakdown voltage controllable by incident light. The dependence of the I–V characteristics on illumination is attributed to the carrier confinement effect in the device operation. © 1998 American Institute of Physics.
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85.60.-q Optoelectronic devices
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors

Tayloring of the optical properties by symmetry modification of substituted quaterthiophene single crystals

G. Gigli, R. Rinaldi, M. Lomascolo, R. Cingolani, G. Barbarella, and M. Zambianchi

Appl. Phys. Lett. 72, 1013 (1998); http://dx.doi.org/10.1063/1.120950 (2 pages) | Cited 8 times

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We report an optical study of polymorphic single crystals of a polysubstituted α-conjugated quaterthiophene. The crystals exhibit two crystalline symmetries (monoclinic and triclinic) with different energy gaps and lifetimes of the elementary excitations. Their optical properties are correlated to the molecular structure, showing that the functionalization process determines an intrinsic tuning of the crystal properties. © 1998 American Institute of Physics.
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42.70.Jk Polymers and organics
61.41.+e Polymers, elastomers, and plastics
71.23.-k Electronic structure of disordered solids
72.15.Nj Collective modes (e.g., in one-dimensional conductors)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

On the optical properties of InAs/InP systems: The role of two-dimensional structures and three-dimensional islands

C. A. C. Mendonça, E. Laureto, M. J. S. P. Brasil, M. A. Cotta, M. M. G. Carvalho, and E. A. Meneses

Appl. Phys. Lett. 72, 1015 (1998); http://dx.doi.org/10.1063/1.120951 (3 pages) | Cited 5 times

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We investigate the effects of the interface morphology on the electronic properties of InAs/In systems using in-air atomic force microscopy and low temperature photoluminescence. Atomic force microscopy results show that the distribution of InAs strained film into three-dimensional islands and the two-dimensional wetting layer—typical of the Stranski–Krastanov growth mode—is strongly affected by the characteristics of the substrate and by the morphology of the InP buffer layer. The differences in the optical data are correlated to the different interface characteristics observed by atomic force microscopy. We discuss the origin of emission peaks taking into account the diffusion process of adsorbed atoms on the different types of surface. © 1998 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.35.Ct Interface structure and roughness
73.61.Ey III-V semiconductors

Optical second-harmonic probe for ultra-high frequency on-chip interconnects with benzocyclobutene

M. Nagel, C. Meyer, H.-M. Heiliger, T. Dekorsy, H. Kurz, R. Hey, and K. Ploog

Appl. Phys. Lett. 72, 1018 (1998); http://dx.doi.org/10.1063/1.120952 (3 pages) | Cited 12 times

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We report the application of electric field-induced second-harmonic (EFISH) generation for time-resolved measurement of ultra-fast electrical pulses propagating on thin-film microstrip lines fabricated with a polymer based on benzocyclobutene as a dielectric layer on a silicon substrate. This contactless field detection enables the characterization of electric pulses on the transmission line up to 1.95 THz. In comparison to external electro-optic sampling the EFISH technique provides a better characterization tool concerning time-resolution and noninvasiveness. © 1998 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.20.Jq Electro-optical effects
84.40.Az Waveguides, transmission lines, striplines
78.47.-p Spectroscopy of solid state dynamics

Large near-resonance third-order nonlinearity in an azobenzene-functionalized polymer film

R. Rangel-Rojo, S. Yamada, H. Matsuda, and D. Yankelevich

Appl. Phys. Lett. 72, 1021 (1998); http://dx.doi.org/10.1063/1.120977 (3 pages) | Cited 32 times

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The third-order nonlinear optical response of a thin film containing the azobenzene dye Disperse Red 1 was studied using the z-scan technique with tunable picosecond pulses. A nonlinear refractive index of −5.0 cm2/GW, corresponding to a Re χ(3) = −3.0×10−15 m2/V2 (2.1×10−7 esu), has been measured at 570 nm. The observed nonlinearity is attributed to the change in refractive index induced by the trans-cis transition in the dye molecule. © 1998 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
78.66.Qn Polymers; organic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Jk Polymers and organics
78.47.-p Spectroscopy of solid state dynamics

All-optical wavelength switching in a semiconductor laser using self-seeding and external injection-seeding

S. P. Yam and C. Shu

Appl. Phys. Lett. 72, 1024 (1998); http://dx.doi.org/10.1063/1.120953 (3 pages) | Cited 2 times

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We developed an approach for efficient optical switching by employing the mechanism of gain competition between two different wavelengths. The lasing wavelengths are obtained by self-seeding and external injection-seeding of the same gain-switched Fabry–Pérot laser diode. A direct comparison shows that the latter yields a faster switching response owing to the injection of continuous oscillations. Optical switching has been demonstrated over a 20 nm tuning range with an injection power as small as 10 μW. An operating bandwidth in the tens of MHz frequency range can be expected using the switching scheme. © 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.Fc Modulation, tuning, and mode locking
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Optical absorption of composites of nanocrystalline silver prepared by electrodeposition

S. Banerjee and D. Chakravorty

Appl. Phys. Lett. 72, 1027 (1998); http://dx.doi.org/10.1063/1.120954 (3 pages) | Cited 18 times

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Silver particles of average diameters in the range 10.3–25.7 nm have been grown within a gel medium by an electrodeposition technique. Detailed optical absorption characteristics in the wavelength range 250–600 nm have been investigated for nanocomposites comprising these particles dispersed in a polystyrene matrix. Absorption maximum occurs at a wavelength around 350 nm, which increases as the metal particle size is increased. Mie theory with the incorporation of a distribution of particle size gives remarkable agreement with the experimental data. The electrical conductivity as extracted from the theoretical analysis for particles with diameters ∼ 3 nm is found to be less than Mott’s minimum metallic conductivity. This indicates the possibility of a metal insulator transition in this system, which appears to be consistent with earlier electrical conductivity measurements. © 1998 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
78.40.Kc Metals, semimetals, and alloys
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
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Laser generation of ultrasound using a modulated continuous wave laser diode

S. G. Pierce, B. Culshaw, and Q. Shan

Appl. Phys. Lett. 72, 1030 (1998); http://dx.doi.org/10.1063/1.120955 (3 pages) | Cited 25 times

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A modulated continuous wave diode laser was used to generate ultrasonic Lamb waves in a thin steel plate. No surface damage was evident on the sample, a feature due to the low power density of the acoustic source in contrast to the high power pulsed laser systems usually employed for laser-ultrasound generation. The Lamb waves were monitored using a surface bonded optical fiber interferometer whose output was correlated with the pseudorandom binary sequence used to modulate the laser diode. In this fashion, it was possible to record a time domain history of the ultrasonic propagation in the sample. © 1998 American Institute of Physics.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
62.65.+k Acoustical properties of solids
43.38.Zp Acoustooptic and photoacoustic transducers
43.38.Rh Surface acoustic wave transducers
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Bg Metals and alloys
79.20.Ds Laser-beam impact phenomena
43.35.Pt Surface waves in solids and liquids
68.35.Gy Mechanical properties; surface strains
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Brominated plastic equation of state measurements using laser driven shocks

M. Koenig, A. Benuzzi, B. Faral, J. Krishnan, J. M. Boudenne, T. Jalinaud, C. Rémond, A. Decoster, D. Batani, D. Beretta, and T. A. Hall

Appl. Phys. Lett. 72, 1033 (1998); http://dx.doi.org/10.1063/1.120956 (3 pages) | Cited 15 times

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In order for brominated plastic (CHBr) to be used in future large lasers, such as the National Ignition Facility, capsule design, and equation of state (EOS) data are needed to address uncertainties in modeling. We have performed CHBr EOS measurements using the impedance matching technique. Laser beams spatially smoothed, and giving a spot size of 400 μm and intensities ⩽ 5×1013 W/cm2, produced high-quality shock waves allowing the simultaneous measurements of the shock velocities in two materials, one used as reference. Results are compared to other experiments and to EOS calculations. We obtained very good agreement with the theoretical curve for pressures ranging from 1 to 3 Mbar. © 1998 American Institute of Physics.
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64.30.-t Equations of state of specific substances
07.20.-n Thermal instruments and apparatus
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n-type electrical conduction in transparent thin films of delafossite-type AgInO2

Takuya Otabe, Kazushige Ueda, Atsushi Kudoh, Hideo Hosono, and Hiroshi Kawazoe

Appl. Phys. Lett. 72, 1036 (1998); http://dx.doi.org/10.1063/1.120957 (3 pages) | Cited 33 times

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Thin films of AgInO2 were prepared to find a transparent and n-type conducting oxide with a delafossite structure. This is a candidate material for fabricating a pn junction with the recently found p type conducting and transparent CuAlO2 delafossite. Nondoped and 5% Sn-doped thin films were deposited on a silica glass substrate by radio-frequency sputtering. The crystalline phase in the films was identified to be the delafossite structure by x-ray diffraction and chemical composition was confirmed to be an Ag/In ratio = 1.00/0.97 by inductively coupled plasma emission spectroscopy. The optical band gap was estimated from absorption spectra to be ∼ 4.4 eV, and the thin films were transparent up to near ultraviolet region. Electrical conductivities of the nondoped and 5% Sn-doped AgInO2 films at room temperature were 1×10−5 and 6×100 S cm−1, respectively. Measurements of Hall voltage and Seebeck coefficient (−50 μV K−1) suggested the conduction in the Sn-doped film to be n type. Carrier concentration and Hall mobility in the doped film were 2.7×1019 cm−3 and 0.47 cm2 V−1 s−1, respectively. © 1998 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Lw Thermoelectric effects
78.66.Li Other semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Fy Semiconductors

Formation of visible light emitting porous GaAs micropatterns

P. Schmuki, L. E. Erickson, D. J. Lockwood, J. W. Fraser, G. Champion, and H. J. Labbé

Appl. Phys. Lett. 72, 1039 (1998); http://dx.doi.org/10.1063/1.120958 (3 pages) | Cited 29 times

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Pore growth on n-type GaAs (100) can be initiated in 1 M HCl solution by electrochemical polarization of the material anodic to a critical potential value—the pore formation potential (PFP). At surface defects, however, the PFP is significantly lower (shifted cathodically). Focused ion beam, implantation of Si++ was used to create defined patterns in the substrate. At these implant sites, the growth of porous GaAs was selectively achieved by polarization below the overall PFP. From the porous GaAs patterns visible photoluminescence at green-yellow wavelengths can be observed. This technique, thus, allows the production of light emitting porous GaAs micropatterns of arbitrary shape by a direct writing process. © 1998 American Institute of Physics.
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85.40.Hp Lithography, masks and pattern transfer
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
81.05.Rm Porous materials; granular materials
82.45.-h Electrochemistry and electrophoresis

Measurement of the electrostrictive coefficients of modified lead magnesium niobate using neutron powder diffraction

S. T. Misture, S. M. Pilgrim, J. C. Hicks, C. T. Blue, E. A. Payzant, and C. R. Hubbard

Appl. Phys. Lett. 72, 1042 (1998); http://dx.doi.org/10.1063/1.120944 (3 pages) | Cited 8 times

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Neutron powder diffraction measurements and a constitutive model were used to determine the bulk longitudinal and transverse electrostrictive coefficients (Qijkl) for polycrystalline samples of the subject material. Effective single-crystal Qijkl were calculated from the powder neutron diffraction data. The resulting values of the three independent Qijkl, as determined from the cubic symmetry of the underlying lattice, are Q3333 = 2.1×10−2 m4/C2, Q3322 = −0.87×10−2 m4/C2, and Q3232 = 1.2×10−2 m4/C2. Using these effective single-crystal values, a random ensemble average was used to predict the electromechanical performance of the polycrystalline material. Predicted values of bulk Q3333 = 1.86×10−2 m4/C2 and Q3322 = −0.78×10−2 m4/C2 are 89% and 87%, respectively, of the effective single-crystal values for Q3333 and Q3322, while measured values of polycrystalline specimens are only ∼ 70% of the single-crystal values. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Bn Piezoelectric and electrostrictive constants
61.05.fm Neutron diffraction

Anisotropic grain noise in eddy current inspection of noncubic polycrystalline metals

Mark Blodgett and Peter B. Nagy

Appl. Phys. Lett. 72, 1045 (1998); http://dx.doi.org/10.1063/1.120959 (3 pages) | Cited 11 times

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This letter discusses the role electrical anisotropy plays in the structural integrity assessment of polycrystalline titanium alloys from the standpoint of fatigue crack detection and the related issue of microstructural noise. In eddy current inspection of noncubic crystallographic classes of polycrystalline metals the electric anisotropy of individual grains produces an inherent microstructural variation or noise that is very similar to the well-known acoustic noise produced by the elastic anisotropy of both cubic and noncubic materials in ultrasonic characterization. The presented results demonstrate that although the electrical grain noise is clearly detrimental in eddy current nondestructive testing for small flaws, it can be also exploited for characterization of the microstructure in noncubic polycrystalline materials such as titanium alloys in the same way acoustic grain noise is used for ultrasonic characterization of the microstructure in different materials. © 1998 American Institute of Physics.
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81.70.Ex Nondestructive testing: electromagnetic testing, eddy-current testing
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.72.-y Defects and impurities in crystals; microstructure

Neutron diffraction study of electrostrictive coefficients of prototype cubic phase of relaxor ferroelectric PbMg1/3 Nb2/3 O3

J. Zhao, A. E. Glazounov, Q. M. Zhang, and Brian Toby

Appl. Phys. Lett. 72, 1048 (1998); http://dx.doi.org/10.1063/1.120960 (3 pages) | Cited 43 times

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The electrostrictive coefficients of prototype cubic phase of PbMg1/3Nb2/3O3 are studied using a high-resolution neutron powder diffraction experiment. The key idea of the approach is to “eliminate” from the material the inhomogeneity related to the presence of the double-phase mixture “polar regions/nonpolar matrix,” and to study two structurally homogeneous states: prototype cubic at temperatures above 600 K and rhombohedral ferroelectric at temperatures below 220 K. The obtained value of volumetric electrostrictive coefficient, Qh = (8.3±1.0)×10−2 ×(m4/C2), is consistent with those of other perovskite ferroelectrics with a prototype cubic phase. © 1998 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Gm Dielectric loss and relaxation
77.65.-j Piezoelectricity and electromechanical effects

X-ray photoelectron spectroscopy study of Bi4Ti3O12 ferroelectric ceramics

Č Jovalekić, M. Pavlović, P. Osmokrović, and Lj. Atanasoska

Appl. Phys. Lett. 72, 1051 (1998); http://dx.doi.org/10.1063/1.120961 (3 pages) | Cited 64 times

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Ferroelectric Bi4Ti3O12 ceramics have been prepared by the method of reactive sintering. The ceramics exhibit good ferroelectric properties with a remanent polarization Pr = 5.5×10−2 C/m2 and a coercive field Ec = 3MV/m. High resolution x-ray photoelectron spectra of the atomic constituents of Bi4Ti3O12 were recorded. The obtained results indicate that oxygen vacancies are preferentially sited in the vicinity of Bi ions, in the Bi2O2 layers. © 1998 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
77.22.Ej Polarization and depolarization
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
79.60.Ht Disordered structures
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Accurate extraction of the diffusion current in silicon p-n junction diodes

E. Simoen, C. Claeys, A. Czerwinski, and J. Katcki

Appl. Phys. Lett. 72, 1054 (1998); http://dx.doi.org/10.1063/1.120962 (3 pages) | Cited 9 times

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An accurate method for the extraction of the reverse diffusion current component in a silicon p-n junction diode is proposed. It combines capacitance–voltage and current–voltage measurements on an array of diodes with different geometry in order to separate the peripheral and the volume leakage current components. The corrected volume capacitance is then used to calculate the depletion width as a function of the reverse bias. Extrapolation of the reverse current to zero depletion width results in the diffusion current part, both for the volume and for the peripheral component. From the temperature dependence, a thermal activation energy of 1.12 eV is obtained. The volume diffusion current density of the p-type Czochralski wafers studied, shows a pronounced substrate dependence, while the peripheral diffusion current density is constant. Finally, the implications for the extraction of the effective bulk recombination lifetime are discussed. © 1998 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Cw Elemental semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
85.30.Kk Junction diodes

An improved analysis for band edge optical absorption spectra in hydrogenated amorphous silicon from optical and photoconductivity measurements

L. Jiao, I. Chen, R. W. Collins, C. R. Wronski, and N. Hata

Appl. Phys. Lett. 72, 1057 (1998); http://dx.doi.org/10.1063/1.120963 (3 pages) | Cited 18 times

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The uncertainties inherent in the normalization of subgap photoconductivity spectra to the optical absorption spectra α(hv) in a-Si:H based films have been addressed. An analysis is presented which is based on optical transitions of constant dipole matrix element between parabolic distributions of extended states and exponential distributions of localized tail states. This analysis has been used to normalize the two sets of results accurately, as verified by photothermal deflection spectroscopy measurements, and is shown to be useful in the commonly encountered cases, in which the two spectra do not overlap over an extended region. Improved quantitative fits of α(hv), for photon energy from ∼ 1.5 to 2.4 eV, obtained on different a-Si:H based films indicate that the localized exponential band tail regions extend ∼ 60–70 meV above the optical gap. © 1998 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.66.Db Elemental semiconductors and insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.61.Jc Amorphous semiconductors; glasses
73.61.Cw Elemental semiconductors
73.50.Pz Photoconduction and photovoltaic effects
78.40.Fy Semiconductors
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
71.55.Jv Disordered structures; amorphous and glassy solids

Polarized electroabsorption spectra and light soaking of solar cells based on hydrogenated amorphous silicon

Lin Jiang, Qi Wang, E. A. Schiff, S. Guha, and J. Yang

Appl. Phys. Lett. 72, 1060 (1998); http://dx.doi.org/10.1063/1.120964 (3 pages) | Cited 1 time

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We present grazing-incidence measurements of polarized electroabsorption spectra in p–i–n solar cells based on hydrogenated amorphous silicon (a-Si:H). We find a significantly stronger polarization dependence in the present measurements compared with earlier work based on electroabsorption detected using coplanar electrodes on a-Si:H thin films. We do not find any significant dependence of the polarized electroabsorption upon light soaking, although this effect was found in previous work with coplanar electrodes. © 1998 American Institute of Physics.
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84.60.Jt Photoelectric conversion
78.66.Jg Amorphous semiconductors; glasses
73.61.Jc Amorphous semiconductors; glasses
78.20.Jq Electro-optical effects
73.50.Pz Photoconduction and photovoltaic effects

Junction devices based on sulfonated polyaniline

M. Narasimhan, M. Hagler, V. Cammarata, and M. Thakur

Appl. Phys. Lett. 72, 1063 (1998); http://dx.doi.org/10.1063/1.120965 (3 pages) | Cited 16 times

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Schottky diodes were fabricated using aluminum/neutralized-sulfonated-polyaniline (SPAN) junctions. I–V and C–V measurements were made, and the barrier height (ΦB) and the background concentration (NB) were determined to be 0.8 V and 4×1017/cm3, respectively. Using these diodes as gate control, depletion-mode thin-film transistors were fabricated with a source and drain made of gold Ohmic contacts. The transistors were characterized by I–V measurements, and the carrier mobility determined from devices operating in the ∣VG∣>∣VDS∣ “linear” regime was about 0.01 cm2/V s. This high value of mobility could be attributed to the spherulitic (partially ordered) structures observed in the SPAN thin films. Field-effect transistors were also fabricated on SPAN films deposited on an n-doped silicon substrate acting as the gate electrode with a thermally grown oxide layer. A reasonably high on/off ratio ( ∼ 4×103) was measured in these devices. © 1998 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Tv Field effect devices
73.61.Ph Polymers; organic compounds

Characterization of high-quality InGaN/GaN multiquantum wells with time-resolved photoluminescence

M. S. Minsky, S. B. Fleischer, A. C. Abare, J. E. Bowers, E. L. Hu, S. Keller, and S. P. Denbaars

Appl. Phys. Lett. 72, 1066 (1998); http://dx.doi.org/10.1063/1.120966 (3 pages) | Cited 42 times

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Recombination in single quantum well and multiquantum well InGaN/GaN structures is studied using time-resolved photoluminescence and pulsed photoluminescence measurements. Room-temperature measurements show a rapid lifetime (0.06 ns) for a single quantum well structure, while an increasingly long decay lifetime is measured for multiquantum wells as more quantum wells are incorporated into the structure. Temperature-dependent lifetime measurements show that a nonradiative recombination mechanism activates above 45 K in the single quantum well but is less important in the multiquantum wells. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics

Electrical characterization of defects introduced in p-Si1−xGex during electron-beam deposition of Sc Schottky barrier diodes

M. Mamor, F. D. Auret, S. A. Goodman, and G. Myburg

Appl. Phys. Lett. 72, 1069 (1998); http://dx.doi.org/10.1063/1.120967 (3 pages) | Cited 17 times

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Scandium (Sc) Schottky barrier diodes were fabricated by electron-beam (EB) deposition on epitaxially grown p-Si1−xGex strained films with x = 0.0–0.2. The EB deposition was performed either with or without shielding the Si1−xGex samples. The barrier height and the defects introduced during EB deposition have been investigated as a function of Ge composition. Our results showed that the barrier height decreased as the band gap changed with increasing Ge content. The defect properties were studied with deep-level transient spectroscopy. The most prominent defect observed in p-Si was a hole trap H(0.53) at Eν+0.53 eV. Increasing the Ge content led to a decrease in the activation energy of this defect and this decrease followed the same trend as the band-gap variation, suggesting that the main defect detected in p-Si1−xGex is the same as that observed in p-Si. © 1998 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices
71.55.Ht Other nonmetals
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Bx Metals, semimetals, and alloys

A novel tool for mapping composition distributions in semiconductor microstructures—application to InxGa1−xP quantum wires

P. Dua, S. L. Cooper, and K. Y. Cheng

Appl. Phys. Lett. 72, 1072 (1998); http://dx.doi.org/10.1063/1.120968 (3 pages) | Cited 5 times

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A technique is described which employs resonant Raman scattering for nondestructive, quantitative analysis of alloy composition distributions and their volume fractions in semiconductor microstructures. Use of this technique is demonstrated via application to extract the wire and barrier region compositions and the shape of the composition modulation profile of narrow ( ∼ 150 Å) InxGa1−xP multiquantum wire array grown via a strain-induced laterally ordered process. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.61.Ey III-V semiconductors
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