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5 Oct 1998

Volume 73, Issue 14, pp. 1925-2058

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Facet roughness analysis for InGaN/GaN lasers with cleaved facets

D. A. Stocker, E. F. Schubert, W. Grieshaber, K. S. Boutros, and J. M. Redwing

Appl. Phys. Lett. 73, 1925 (1998); http://dx.doi.org/10.1063/1.122172 (3 pages) | Cited 11 times

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Atomic force microscope images reveal a root-mean-square roughness Δd = 16 nm for InGaN/GaN double-heterostructure laser structures with cleaved a-plane facets. The c-plane sapphire substrate cleaves cleanly along both the a and m planes. A theoretical model is developed which shows that the power reflectivity of the facets decreases with roughness by a factor of e−16π2(nΔd/λ0)2, where n is the refractive index of the semiconductor and λ0 is the emission wavelength. Laser emission from the optically pumped cavities shows a TE/TM ratio of 100, an increase in differential quantum efficiency by a factor of 34 above threshold, and an emission line narrowing to 13.5 meV. © 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
68.35.B- Structure of clean surfaces (and surface reconstruction)
42.86.+b Optical workshop techniques
68.55.-a Thin film structure and morphology

Demonstration of an InGaN/GaN-based optically pumped multiquantum well distributed feedback laser using holographically defined third-order gratings

Daniel Hofstetter, Robert L. Thornton, Michael Kneissl, David P. Bour, and Clarence Dunnrowicz

Appl. Phys. Lett. 73, 1928 (1998); http://dx.doi.org/10.1063/1.122325 (3 pages) | Cited 8 times

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We demonstrate an optically pumped InGaN/GaN-based multiquantum well distributed feedback laser in the blue spectral region. The third-order grating providing feedback was defined holographically and dry etched into the upper waveguiding layer by chemically assisted ion-beam etching. When aligning the stripe-shaped pump beam either parallel or perpendicular to the grating grooves, we found a considerably lower pumping threshold, higher slope efficiency, a slightly longer emission wavelength, and a much narrower linewidth for the geometry with the pump beam orthogonal to the grating lines. A nearly constant emission wavelength of 400.85 nm and a linewidth of 0.7 Å were observed under various pump intensities. To the best of our knowledge, this is the narrowest linewidth ever reported for an optically pumped device in this material system. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.40.Eq Holographic optical elements; holographic gratings

Cleaved cavity stimulated emission from an optically pumped cubic GaN/AlGaN heterostructure grown on GaAs (100) substrate

J. Wu, H. Yaguchi, K. Onabe, and Y. Shiraki

Appl. Phys. Lett. 73, 1931 (1998); http://dx.doi.org/10.1063/1.122326 (3 pages) | Cited 8 times

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Cubic GaN/AlGaN double heterostructure was grown on semi-insulating GaAs (100) substrate by metalorganic vapor phase epitaxy. Strong stimulated emission was observed from the cleaved edge of the optically pumped cubic GaN/AlGaN heterostructure at 15 K. The cavity was formed simply by cleaving the substrate. The stimulated emission was demonstrated by the superlinear increase of the output intensity and the highly transverse electric polarized nature. The stimulated emission showed an obvious redshift compared with the spontaneous one. © 1998 American Institute of Physics.
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78.45.+h Stimulated emission
42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors
42.60.By Design of specific laser systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Ultrafast optical pulse noise suppression using a nonlinear spectral filter: 23 dB reduction of fiber laser 1/f noise

Stephen R. Friberg and Susumu Machida

Appl. Phys. Lett. 73, 1934 (1998); http://dx.doi.org/10.1063/1.122327 (3 pages) | Cited 2 times

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Nonlinear spectral filtering provides a simple method for reducing noise in optical pulses to below the shot noise level. We show its effectiveness for excess noise reduction in an ultrafast optical pulse train by demonstrating 23 dB reduction of low frequency 1/f noise in pulses from a passively mode-locked erbium-doped fiber laser. The noise reduction is achieved by spectrally filtering pulses propagated as solitons through a 1.5 km length of optical fiber. © 1998 American Institute of Physics.
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42.55.Wd Fiber lasers
42.60.Mi Dynamical laser instabilities; noisy laser behavior
42.79.Ci Filters, zone plates, and polarizers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking
42.65.Tg Optical solitons; nonlinear guided waves

Normal-incidence intersubband (In, Ga)As/GaAs quantum dot infrared photodetectors

Dong Pan, Elias Towe, and Steve Kennerly

Appl. Phys. Lett. 73, 1937 (1998); http://dx.doi.org/10.1063/1.122328 (3 pages) | Cited 151 times

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We report the device performance of normal-incidence (In, Ga)As/GaAs quantum dot intersubband infrared photodetectors. A primary intersubband transition peak is observed at the wavelength of 13 μm (E0→E1) and a secondary peak at 11 μm (E0→E2). The measured energy spacing in the conduction band of the quantum dots is in good agreement with low temperature photoluminescence measurement and calculations. A peak detectivity of 1×1010 cm Hz1/2/W at 13 μm was achieved at 40 K for these devices. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.61.Ey III-V semiconductors

Optically induced polarization rotations in CdTe/CdMnTe multiple quantum wells

M. Haddad, P. Leisching, R. Frey, C. Flytzanis, and J. Cibert

Appl. Phys. Lett. 73, 1940 (1998); http://dx.doi.org/10.1063/1.122329 (3 pages) | Cited 1 time

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We report large polarization state rotations of a weak pulsed beam in CdTe/CdMnTe quantum wells photoinduced by intense circularly polarized pulsed pump beam. Time-resolved analysis of the effect shows that, at moderate pump fluences, the polarization state rotation is due to the combined effect of many-body interactions and spectral hole burning at early times and to photoinduced magnetization at longer ones. At higher pump fluences, space filling and degenerate four-wave mixing become important. At low pump fluences (few μJ/cm2) already the polarization rotation photoinduced at early times can be as large as a few degrees making these multiple quantum wells potential candidates for applications. © 1998 American Institute of Physics.
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78.20.Ek Optical activity
78.66.Hf II-VI semiconductors
75.50.Pp Magnetic semiconductors
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Design of one-dimensional band-limited uniform diffusers of light

T. A. Leskova, A. A. Maradudin, I. V. Novikov, A. V. Shchegrov, and E. R. Méndez

Appl. Phys. Lett. 73, 1943 (1998); http://dx.doi.org/10.1063/1.122330 (3 pages) | Cited 5 times

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We present two methods for generating numerically a one-dimensional random surface, defined by the equation x3 = ζ(x1), that has a prescribed probability density function of slopes. This problem arises in the design of a diffuser that scatters light uniformly within a range of scattering angles and produces no scattering outside this range. Numerical calculations of the scattering of light from random surfaces generated by these approaches show that the scattered intensity, indeed, has a rectangular distribution as a function of the scattering angle. © 1998 American Institute of Physics.
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42.25.Fx Diffraction and scattering
02.50.Cw Probability theory
02.60.-x Numerical approximation and analysis

Integrated optical isolator based on efficient nonreciprocal radiation mode conversion

Toshihiro Shintaku

Appl. Phys. Lett. 73, 1946 (1998); http://dx.doi.org/10.1063/1.122331 (3 pages) | Cited 39 times

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An integrated optical isolator is demonstrated based on efficient nonreciprocal conversion from a fundamental TM mode to a deep TE radiation mode away from the cutoff. The isolator is realized using a single-mode rib channel waveguide in Ce-substituted yttrium iron garnet, which has a very large Faraday rotation. 27 dB isolation is obtained at a wavelength of 1535 nm. © 1998 American Institute of Physics.
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85.70.Ge Ferrite and garnet devices
78.20.Ls Magneto-optical effects
42.82.Et Waveguides, couplers, and arrays
42.65.Wi Nonlinear waveguides
75.50.Gg Ferrimagnetics
42.79.Gn Optical waveguides and couplers

Superradiant lasing from J-aggregated molecules adsorbed onto colloidal silver

Serdar Özçelik, Isin Özçelik, and Daniel L. Akins

Appl. Phys. Lett. 73, 1949 (1998); http://dx.doi.org/10.1063/1.122563 (3 pages) | Cited 18 times

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The picosecond time-resolved emission spectrum of the cyanine dye 1,1′-diethyl-3,3′bis-(3-sulfopropyl)-5,5′,6,6′-tetrachlorobenzimidazolocarbocyanine (also known as BIC) adsorbed onto colloidal silver was examined as a function of laser pulse energy at room temperature. BIC is found to aggregate on colloidal silver, and the number of coherently responding molecules involved in the one-exciton state (i.e., the coherence length) was estimated to involve 8–9 molecules. Lasing at a remarkably low incident pulse energy threshold was found for this system and explained in terms of a mechanism involving superradiant states created in coherently coupled adsorbed molecules that emit photons which stimulate emission from other spatially distributed superradiant states. © 1998 American Institute of Physics.
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42.55.Mv Dye lasers
78.45.+h Stimulated emission
42.50.Nn Quantum optical phenomena in absorbing, amplifying, dispersive and conducting media; cooperative phenomena in quantum optical systems
78.66.Qn Polymers; organic compounds
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Poisson’s ratio measurement in tungsten thin films combining an x-ray diffractometer with in situ tensile tester

P.-O. Renault, K. F. Badawi, L. Bimbault, Ph. Goudeau, E. Elkaïm, and J. P. Lauriat

Appl. Phys. Lett. 73, 1952 (1998); http://dx.doi.org/10.1063/1.122332 (3 pages) | Cited 24 times

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A direct determination of the Poisson’s ratio in 150 nm polycrystalline tungsten thin films deposited by ion-beam sputtering on Duralumin substrates has been performed by combining x-ray diffraction measurements with in situ traction on the sample. X-ray diffraction experiments using the sin2 ψ method have been done at LURE, the French synchrotron facility (Orsay, France) on a four-circle diffractometer. The method described in this letter allows us to extract in a simple way and with a good precision the Poisson’s ratio of thin films on substrates from the evolution of the sin2 ψ curves as a function of applied strains. In the case of tungsten thin film, the value obtained is close to the bulk material one. © 1998 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity

Analytical transmission electron microscopy of hydrogen-induced degradation in ferroelectric Pb(Zr, Ti)O3 on a Pt electrode

Nobuyuki Ikarashi

Appl. Phys. Lett. 73, 1955 (1998); http://dx.doi.org/10.1063/1.122333 (3 pages) | Cited 31 times

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Changes in the crystal structure of Pb(Zr, Ti)O3 (PZT) on a Pt electrode caused by annealing in hydrogen-containing ambient have been studied using analytical transmission electron microscopy. A decrease in Pb composition and distortion in Ti–O coordination occur at the PZT/Pt interface. These findings indicate that preferential reduction of Pb and sequential diffusion of Pb from the PZT to the Pt electrode play an important role in the changes of the PZT crystal. Thus, changes in crystal structure due to annealing in a hydrogen-containing ambient can be avoided by using electrode materials that prevent Pb diffusion. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.Fx Diffusion; interface formation
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
61.72.Cc Kinetics of defect formation and annealing

Laser-assisted low temperature processing of Pb(Zr, Ti)O3 thin film

Yongfei Zhu, Jinsong Zhu, Yoon J. Song, and S. B. Desu

Appl. Phys. Lett. 73, 1958 (1998); http://dx.doi.org/10.1063/1.122334 (3 pages) | Cited 25 times

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A method for lowering the processing temperature of PbZr1−xTixO3 (PZT) films was developed utilizing a laser-assisted two-step process. In the first step, perovskite phase was initiated in the PZT films to a furnace anneal at low temperatures in the range of 470–550 °C, depending on the Zr/Ti ratio. Later, the films were laser annealed (using KrF excimer laser) at room temperature to grow the perovskite phase, and to improve microstructure and ferroelectric properties. It was found that this two-step process was very effective in producing excellent quality ferroelectric PZT films at low temperatures. It should be noted that although laser annealing of amorphous and/or pyrochlore films directly (one-step process) produced perovskite phase, the ferroelectric properties of these films, irrespective of the composition, were rather unattractive. Some possible reasons for the ineffectiveness of the one-step process were discussed. © 1998 American Institute of Physics.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.72.Cc Kinetics of defect formation and annealing

Reversible bending of carbon nanotubes using a transmission electron microscope

Walter H. Knechtel, Georg S. Düsberg, Werner J. Blau, Eduardo Hernández, and Angel Rubio

Appl. Phys. Lett. 73, 1961 (1998); http://dx.doi.org/10.1063/1.122335 (3 pages) | Cited 17 times

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Multiwall carbon nanotubes can be bent by changing the current density of the electron beam in a transmission electron microscope. The effect could be observed in a small fraction of nanotubes in the investigated samples. The bending can be varied continuously, is reversible, and highly reproducible. On removing the force which makes them bend, they relax to their originally straight shape without any damage, thus exhibiting spring-like behavior. Possible mechanisms for this effect are discussed. © 1998 American Institute of Physics.  
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61.46.-w Structure of nanoscale materials
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
62.20.F- Deformation and plasticity
36.40.-c Atomic and molecular clusters
81.05.ub Fullerenes and related materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Electronic origin of the stability trend in TiSi2 phases with Al or Mo layers

F. Bònoli, M. Iannuzzi, Leo Miglio, and V. Meregalli

Appl. Phys. Lett. 73, 1964 (1998); http://dx.doi.org/10.1063/1.122336 (3 pages) | Cited 24 times

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Through a tight-binding rigid-band approach we show that changes in the relative stability of the C54, C49, and C40 phases of TiSi2, with electrons per atom ratio, are produced by the corresponding differences in the electronic density of states at the Fermi level. In particular, by increasing this ratio the stable phase evolves from C49 to C54, and then to C40. Our microscopic model provides a straightforward interpretation of very recent experimental findings concerning the sizeable variations in the transition temperature between C49 and C54 TiSi2 in the presence of Al or Mo layers. © 1998 American Institute of Physics.
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61.66.Fn Inorganic compounds
68.60.Dv Thermal stability; thermal effects
71.20.Lp Intermetallic compounds

Growth of CaF2 on Si(111): Imaging of the CaF interface by friction force microscopy

Andreas Klust, Holger Pietsch, and Joachim Wollschläger

Appl. Phys. Lett. 73, 1967 (1998); http://dx.doi.org/10.1063/1.122337 (3 pages) | Cited 5 times

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The initial growth state of CaF2/Si(111) has been investigated in the high-temperature regime (700 °C). At these growth temperatures the interface between CaF2 and Si consists of CaF with the Ca atoms bound to the Si. Using friction force microscopy it is possible to distinguish between the interfacial CaF layer and the overgrowing CaF2 with high lateral resolution: the CaF layer has a higher friction coefficient than the bulklike CaF2. This material contrast has been used to investigate the CaF2 nucleation on the interfacial CaF layer. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)

Atomic transport across the interfaces during the formation of ultrathin silicon oxide/nitride/oxide films

I. J. R. Baumvol, T. D. M. Salgado, C. Radtke, C. Krug, and J. de Andrade

Appl. Phys. Lett. 73, 1970 (1998); http://dx.doi.org/10.1063/1.122338 (3 pages) | Cited 3 times

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The redistribution of O and N during the final, thermal oxidation in dry O2 step in the formation of ultrathin silicon oxide/nitride/oxide dielectric films (ONO) was investigated using isotopic tracing and depth profiling with nanometer resolution. The results show that the final oxidation step induces atomic transport of O and N species in the system, such that the formed ONO structures are not stacked layer structures, but rather a silicon oxynitride ultrathin film, having moderate concentrations of N in the near-surface and near-interface regions, and a high N concentration in the bulk. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Fx Diffusion; interface formation
77.55.-g Dielectric thin films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.65.Mq Oxidation
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Effect of hydrogen on Pb(Zr,Ti)O3-based ferroelectric capacitors

S. Aggarwal, S. R. Perusse, C. W. Tipton, R. Ramesh, H. D. Drew, T. Venkatesan, D. B. Romero, V. B. Podobedov, and A. Weber

Appl. Phys. Lett. 73, 1973 (1998); http://dx.doi.org/10.1063/1.122339 (3 pages) | Cited 98 times

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The properties of ferroelectric films are known to degrade when subjected to hydrogen in forming gas anneals. Earlier studies have attributed this degradation to the loss of oxygen from these films during these anneals. In this study, we show that though oxygen is lost during forming gas annealing, hydrogen incorporation is the primary mechanism for the degradation of ferroelectric properties. Raman spectra obtained from the forming gas-annealed films show evidence of polar hydroxil [OH−] bonds in the films. The most probable site for hydrogen ions is discussed based on ionic radii, crystal structure, electrical properties, and Raman spectra. We propose that the hydrogen ion is bonded with one of the apical oxygen ions and prevents the Ti ion from switching. Pyroelectric measurements on forming gas-annealed capacitors confirm that the capacitors no longer possess spontaneous polarization. © 1998 American Institute of Physics.
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84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
78.30.Hv Other nonmetallic inorganics
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.70.+a Pyroelectric and electrocaloric effects

Nanometer-scale patterning of self-assembled monolayer films on native silicon oxide

A. Inoue, T. Ishida, N. Choi, W. Mizutani, and H. Tokumoto

Appl. Phys. Lett. 73, 1976 (1998); http://dx.doi.org/10.1063/1.122340 (3 pages) | Cited 12 times

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A nanoscale-patterning method on silicon oxide using a self-assembled monolayer (SAM) was developed. The silicon surface with native oxide was additionally oxidized locally in dry nitrogen atmosphere by the field-induced oxidation (FIO) technique using an atomic force microscope with a conductive cantilever, and then immersed in octadecyltrichlorosilane (OTS) solution. The contact angle and topography image revealed that the OTS layer was formed only on the native oxide. In contrast, when FIO was performed under the humidity of 88%, OTS SAM was formed on both FIO and native oxide. These results indicate that SAM formation on silicon oxides can be locally suppressed by FIO in a dry environment. By using this technique, we could fabricate a line structure of OTS SAM as narrow as 22 nm. © 1998 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.60.Bs Mechanical and acoustical properties
81.65.Cf Surface cleaning, etching, patterning
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Alloy ordering in GaInP alloys: A cross-sectional scanning tunneling microscopy study

N. Liu, C. K. Shih, J. Geisz, A. Mascarenhas, and J. M. Olson

Appl. Phys. Lett. 73, 1979 (1998); http://dx.doi.org/10.1063/1.122341 (3 pages) | Cited 20 times

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We present a cross-sectional scanning tunneling microscopy (XSTM) study of the spontaneous ordering of Ga0.48In0.52P and Ga0.52In0.48P grown on (001) GaAs substrates by molecular beam epitaxy (MBE) and organometallic vapor phase epitaxy (OMVPE), respectively. The (111)-type alloy ordering could be seen clearly in the OMVPE-grown alloy region. On the other hand, the MBE-grown region shows a very small degree of ordering as revealed by the STM. Most of the ordered region shows (InP)1(GaP)1-type ordering: alternating InP- and GaP-like (math11) planes. In addition to this type of ordering, we also observe another type of ordering consisting of two InP-like (math11) planes and one GaP-like (math11) plane that we call (InP)2(GaP)1-type ordering. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Single-electron effects in slim semiconductor superlattices

T. Schmidt, R. J. Haug, K. v. Klitzing, and K. Eberl

Appl. Phys. Lett. 73, 1982 (1998); http://dx.doi.org/10.1063/1.122342 (3 pages) | Cited 2 times

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We fabricated laterally confined GaAs–AlGaAs superlattices with diameters between 500 nm and 2 μm. With decreasing device diameter, a gap evolves in the current–voltage curve around zero bias and steps show up at the onset of the current. This behavior is interpreted in terms of Coulomb blockade, a depletion of the center of the superlattice, and single-electron tunneling through donor levels. © 1998 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.23.Hk Coulomb blockade; single-electron tunneling
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Temperature and stress polarity-dependent dielectric breakdown in ultrathin gate oxides

Koji Eriguchi and Masaaki Niwa

Appl. Phys. Lett. 73, 1985 (1998); http://dx.doi.org/10.1063/1.122343 (3 pages) | Cited 12 times

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Temperature and stress polarity-dependent dielectric breakdown in thin silicon dioxides has been carefully investigated. The experimental data show that the time to breakdown under a constant-current injection has two kinks around 330 and 230 K for 4- and 10-nm-thick oxides under both stress polarities. It has been found that thinner oxides have a stronger temperature dependence (a larger activation energy) even if the field dependence of the activation energy is taken into consideration, and also that, from the gate voltage shift during the constant-current injection, the postbreakdown characteristics strongly depends on the stress polarity for thinner oxides. © 1998 American Institute of Physics.
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84.32.Tt Capacitors
85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.22.Jp Dielectric breakdown and space-charge effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Characterization of a semi-insulating GaAs photoconductive semiconductor switch for ultrawide band high power microwave applications

N. E. Islam, E. Schamiloglu, and C. B. Fleddermann

Appl. Phys. Lett. 73, 1988 (1998); http://dx.doi.org/10.1063/1.122344 (3 pages) | Cited 20 times

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Simulation results depicting physical conditions in a photoconductive semiconductor switch in the pulse charging state, prior to high power switching, are analyzed. Results show that surface conditions and EL2 traps in semi-insulating GaAs influence the conduction process, specifically at high bias. Formation of trap-filled regions renders the device inhomogeneous for stable conduction and premature breakdown occurs, due to a large extent on unstable current filamentation within the device. Unlike insulators, the breakdown of desorbed gas from the surface (surface flashover) does not contribute to premature breakdown. © 1998 American Institute of Physics.
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85.60.Bt Optoelectronic device characterization, design, and modeling
85.30.De Semiconductor-device characterization, design, and modeling
84.32.Dd Connectors, relays, and switches
84.40.-x Radiowave and microwave (including millimeter wave) technology

19.8% efficient “honeycomb” textured multicrystalline and 24.4% monocrystalline silicon solar cells

Jianhua Zhao, Aihua Wang, Martin A. Green, and Francesca Ferrazza

Appl. Phys. Lett. 73, 1991 (1998); http://dx.doi.org/10.1063/1.122345 (3 pages) | Cited 203 times

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Multicrystalline silicon wafers, widely used in commercial photovoltaic cell production, traditionally give much poorer cell performance than monocrystalline wafers (the previously highest performance laboratory devices have solar energy conversion efficiencies of 18.6% and 24.0%, respectively). A substantially improved efficiency for a multicrystalline silicon solar cell of 19.8% is reported together with an incremental improvement in monocrystalline cell efficiency to 24.4%. The improved multicrystalline cell performance results from enshrouding cell surfaces in thermally grown oxide to reduce their detrimental electronic activity and from isotropic etching to form an hexagonally symmetric “honeycomb” surface texture. This texture reduces reflection loss as well as substantially increasing the cell’s effective optical thickness by causing light to be trapped within the cell by total internal reflection. © 1998 American Institute of Physics.
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84.60.Jt Photoelectric conversion

Optical band gap in Ga1−xInxN (0<x<0.2) on GaN by photoreflection spectroscopy

C. Wetzel, T. Takeuchi, S. Yamaguchi, H. Katoh, H. Amano, and I. Akasaki

Appl. Phys. Lett. 73, 1994 (1998); http://dx.doi.org/10.1063/1.122346 (3 pages) | Cited 104 times

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The optical band gap in 40 nm Ga1−xInxN/GaN single heterostructures is investigated in the composition range 0<x<0.2 by photoreflection spectroscopy (PR) at room temperature and compared with photoluminescence (PL) data. Clear PR oscillations at the GaInN band gap are observed as originating in the large piezoelectric field. Effective band gap bowing parameters b are derived for pseudomorphically stressed GaInN on GaN: b = 2.6 eV (PR) and b = 3.2 eV (PL in localized states). Using experimental deformation potentials of GaN, b = 3.8 eV is extrapolated for the optical band gap in relaxed GaInN material. Previously reported smaller values are discussed. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.-e Optical properties of bulk materials and thin films

Polarization dependence of intraband absorption in self-organized quantum dots

S. J. Chua, S. J. Xu, X. H. Zhang, X. C. Wang, T. Mei, W. J. Fan, C. H. Wang, J. Jiang, and X. G. Xie

Appl. Phys. Lett. 73, 1997 (1998); http://dx.doi.org/10.1063/1.122347 (3 pages) | Cited 13 times

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Photoluminescence and intraband absorption were investigated in n-doped self-organized InAs and In0.35Ga0.65As quantum dots grown on a GaAs substrate. Intraband absorption of the dots is strongly polarized along the growth axis in the mid infrared spectral range. The absorption is maximum at around 120 meV for InAs dots and at 130 meV for In0.35Ga0.65As dots. The experimental results on InAs dots are in agreement with published theoretical calculations. © 1998 American Institute of Physics.
Show PACS
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
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