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21 Oct 1996

Volume 69, Issue 17, pp. 2453-2609

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Optical transitions in GaN/AlxGa1−xN multiple quantum wells grown by molecular beam epitaxy

M. Smith, J. Y. Lin, H. X. Jiang, A. Salvador, A. Botchkarev, W. Kim, and H. Morkoc

Appl. Phys. Lett. 69, 2453 (1996); http://dx.doi.org/10.1063/1.117495 (3 pages) | Cited 45 times

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Time‐resolved photoluminescence was employed to study optical transitions in GaN/AlxGa1−xN multiple quantum wells (MQWs). The effects of quantum confinement on the optical transitions as well as on the exciton‐phonon interactions in MQW were investigated. Recombination lifetimes of optical transitions were measured at different emission energies and temperatures from 10 to 300 K. It was found that the exciton recombination lifetime increases linearly with temperature up to 60 K, which is a hallmark of radiative exciton recombination in MQW. Observed optical transitions and their dynamics in GaN/AlxGa1−xN MQW were also compared with those in GaN epilayers and GaAs/ AlxGa1−xAs MQW. © 1996 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Quantum cascade disk lasers

Jerôme Faist, Claire Gmachl, Marinella Striccoli, Carlo Sirtori, Federico Capasso, Deborah L. Sivco, and Alfred Y. Cho

Appl. Phys. Lett. 69, 2456 (1996); http://dx.doi.org/10.1063/1.117496 (3 pages) | Cited 40 times

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The fabrication and characterization of quantum cascade (QC) disk lasers at 5 μm wavelength is reported. The QC scheme yields several advantages for the disk geometry: an inherently transverse magnetic polarization, tailorable wavelength, and unipolar carrier transport. The low loss whispering gallery resonator allows small devices, 17–125 μm in diameter, and low threshold currents (2.85 mA for a 17 μm diameter disk) with a size independent pulsed threshold current density of 1.2 kAcm−2 at 15 K. From the threshold current density the quality factor of the disks is estimated at Q∼3500. The emission spectra show single and multiple whispering gallery modes. © 1996 American Institute of Physics.
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42.55.Sa Microcavity and microdisk lasers
78.66.Fd III-V semiconductors

Holographic recording in indium–oxide (In2O3) and indium–tin–oxide (In2O3:Sn) thin films

S. Mailis, L. Boutsikaris, N. A. Vainos, C. Xirouhaki, G. Vasiliou, N. Garawal, G. Kiriakidis, and H. Fritzsche

Appl. Phys. Lett. 69, 2459 (1996); http://dx.doi.org/10.1063/1.117497 (3 pages) | Cited 9 times

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Holographic recording in polycrystalline indium–oxide (InOx) and indium–tin–oxide (ITO) thin films, grown by dc magnetron sputtering, is demonstrated. This recording, performed at relatively low optical power levels in the ultraviolet (UV) wavelength range (325 nm), exhibits very large coupling strength and a slow but dynamic behavior. The observed phenomena are attributed to localized photorefractive effects and appear to be independent of the electrical characteristics of the films. © 1996 American Institute of Physics.
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42.40.Ht Hologram recording and readout methods
78.66.Li Other semiconductors

Resonant‐cavity photodiode operating at 1.55 μm with Burstein‐shifted In0.53Ga0.47As/InP reflectors

S. S. Murtaza, R. V. Chelakara, R. D. Dupuis, J. C. Campbell, and A. G. Dentai

Appl. Phys. Lett. 69, 2462 (1996); http://dx.doi.org/10.1063/1.117498 (3 pages) | Cited 7 times

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Traditionally, mirror design at the wavelengths important for fiber optic systems (1.3 and 1.55 μm) has suffered from the low refractive index step available between InP and its lattice‐matched alloys; the InP/In0.53Ga0.47As combination provides the largest index step, but at λ=1.55 μm absorption in the In0.53Ga0.47As layers degrades reflectivity. We have used the Burstein shift in n+:In0.53Ga0.47As to reduce the band‐to‐band absorption. This has yielded InP/In0.53Ga0.47As Bragg reflectors with reflectivity greater than 97%. These mirrors have been incorporated into a high‐efficiency resonant‐cavity photodetector operating at 1.55 μm. © 1996 American Institute of Physics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
85.60.Dw Photodiodes; phototransistors; photoresistors

Time‐resolved pump‐probe experiments with subwavelength lateral resolution

A. Vertikov, M. Kuball, A. V. Nurmikko, and H. J. Maris

Appl. Phys. Lett. 69, 2465 (1996); http://dx.doi.org/10.1063/1.117499 (3 pages) | Cited 29 times

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We demonstrate picosecond time‐resolved pump‐probe experiments with subwavelength resolution using a reflection near‐field scanning optical microscope (NSOM). The sample was a laterally patterned gold nanostructure. Strain‐induced reflectivity changes as low as ΔR/R≊10−4 were detected in the near‐field. © 1996 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
78.47.-p Spectroscopy of solid state dynamics
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Unusual enhancement of transient reflecting grating signal under a surface plasmon resonance condition

Kenji Katayama, Qing Shen, Akira Harata, and Tsuguo Sawada

Appl. Phys. Lett. 69, 2468 (1996); http://dx.doi.org/10.1063/1.117500 (3 pages) | Cited 8 times

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Subnanosecond time‐resolved transient reflecting grating (TRG) measurements were carried out under resonance conditions of surface plasmon (SP) with a Kretschmann configuration using a 40‐nm‐thick gold film deposited on a hemicylindrical prism. The TRG was generated and detected with two pump beams and with one probe beam incident from the prism side, the angles of which for incidence and polarization were changed. When the pump beams resonantly excited SPs, the TRG signal amplitude was enhanced as expected. An unusual enhancement was observed when the probe beam excited SPs, i.e., the TRG signal amplitude was also enhanced strongly although reflecting diffraction was probed under the less reflective condition. This enhancement was accompanied by a transient wave form change. The mechanism of these phenomena is discussed. © 1996 American Institute of Physics.
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42.79.Dj Gratings
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Bz Metals and metallic alloys

Near‐field scanning optical microscopy of polarization bistable laser diodes

Ch. Lienau, A. Richter, A. Klehr, and T. Elsaesser

Appl. Phys. Lett. 69, 2471 (1996); http://dx.doi.org/10.1063/1.117501 (3 pages) | Cited 12 times

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TE/TM polarization bistability in a λ=1.3 μm ridge‐waveguide InGaAsP/InP bulk laser is studied by near‐field scanning optical microscopy with an optical resolution of better than λ/8. The near‐field mode profiles of TE and TM emission show different lateral widths and distinctly different mode center positions. This lateral shift is related to a nonuniform strain distribution along the active layer. Based on this strain gradient, we present a model that accounts for the hysteresislike current dependence of the polarization resolved laser output. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
07.79.Fc Near-field scanning optical microscopes

Optical control of coherent optical phonons in bismuth films

M. Hase, K. Mizoguchi, H. Harima, S. Nakashima, M. Tani, K. Sakai, and M. Hangyo

Appl. Phys. Lett. 69, 2474 (1996); http://dx.doi.org/10.1063/1.117502 (3 pages) | Cited 79 times

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Interference of impulsively excited coherent phonons in semimetals has been studied by using a double‐pulse pump–probe technique. Enhancement of the oscillation amplitude of an A1g mode is observed when the separation time of the double‐pulse is matched to the period of the phonon oscillation, and a cancellation is observed when the separation time is adjusted to half the period of the phonon oscillation. The amplitude after the second pulse shows a sinusoidal dependence as a function of the separation time, and this dependence is explained in terms of a superposition of two coherent phonon oscillations. In addition, not only the A1g mode but also an Eg mode have been observed by electro‐optic sampling. © 1996 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.66.Bz Metals and metallic alloys

Neutron diffraction measurement of stress‐induced transformation in superelastic NiTi

M. A. M. Bourke, R. Vaidyanathan, and D. C. Dunand

Appl. Phys. Lett. 69, 2477 (1996); http://dx.doi.org/10.1063/1.117503 (3 pages) | Cited 22 times

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The formation of stress‐induced martensite in superelastic NiTi was studied by neutron diffraction during uniaxial compressive loading and unloading. The respective phase fractions were determined as a function of the applied stresses using a Rietveld refinement with a March–Dollase texture formulation. Before loading, the specimen was fully austenitic. At the highest applied stress of −625 MPa, about 90% of the austenitic phase had transformed to martensite, with a concomitant macroscopic strain of −2.8%. Upon unloading, all of the stress‐induced martensite reverted to austenite and the totality of the macroscopic strain was recovered. The propensity for various austenitic crystallographic orientations to transform at different stresses was determined and qualitative observation of this incipient texture in the austenite and of the inherent texture in the nascent martensite are reported. © 1996 American Institute of Physics.
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81.30.Kf Martensitic transformations
81.40.Jj Elasticity and anelasticity, stress-strain relations
61.05.fm Neutron diffraction

Polarity determination of GaN films by ion channeling and convergent beam electron diffraction

B. Daudin, J. L. Rouvière, and M. Arlery

Appl. Phys. Lett. 69, 2480 (1996); http://dx.doi.org/10.1063/1.117504 (3 pages) | Cited 113 times

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By using ion channeling and convergent beam electron diffraction techniques, we have determined the absolute polarity of various GaN films grown by MOCVD on (0001) sapphire. We observe two main classes of GaN films, namely flat and rough pyramidal ones. We find that flat GaN films have a Ga polarity. Rough pyramidal samples contain many tiny columnar inversion domains (with Ga polarity) imbedded in a matrix exhibiting an N polarity. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.05.jm Convergent-beam electron diffraction, selected-area electron diffraction, nanodiffraction
61.05.Np Atom, molecule, and ion scattering (for structure determination only)

Oxygen ion beam‐induced abnormal surface topographic development at Ta/Si interface

Kyung Joong Kim, Kyung‐Hoon Jung, and Dae Won Moon

Appl. Phys. Lett. 69, 2483 (1996); http://dx.doi.org/10.1063/1.117505 (3 pages) | Cited 1 time

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We report on an abnormal surface topographic development at a Ta/Si interface, which is believed to be one of the major sources of the irregular interface artifacts in secondary ion mass spectrometry depth profiling by oxygen ion beam. Round crater type topographic development was observed at the interface by sputtering with a 7 keV O+2 ion beam and was found to have been formed by blister formation and gradual opening of its center. We suggest that the driving force for this abnormal topographic development is a buildup of compressive stress caused by a volume increase of the Ta layer near the interface, due to oxidation. © 1996 American Institute of Physics.
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68.35.Ct Interface structure and roughness
61.80.Jh Ion radiation effects
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Electromigration damage due to copper depletion in Al/Cu alloy conductors

J. R. Lloyd and J. J. Clement

Appl. Phys. Lett. 69, 2486 (1996); http://dx.doi.org/10.1063/1.117506 (3 pages) | Cited 22 times

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The problem of damage nucleation due to electromigration‐induced copper depletion in an Al/Cu alloy is treated. The diffusion of aluminum in thin‐film lines is sharply reduced by alloying with small amounts of copper. In this model, copper is depleted in a region at the cathode end of an Al/Cu alloy line. Assuming that the aluminum diffusion in this copper‐deficient region is much faster than the diffusion of the copper, a quasisteady‐state stress profile is established between the blocking boundary at the cathode and the copper front moving at the drift velocity. The time to reach a critical stress to initiate failure is shown to depend on the inverse of the square of the current density as observed experimentally. The model is appropriate for failure at contacts and vias, and at the end of long polycrystalline clusters in near‐bamboo lines. © 1996 American Institute of Physics.
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66.30.Qa Electromigration
73.61.At Metal and metallic alloys

Limitations to n‐type doping in diamond: The phosphorus‐vacancy complex

R. Jones, J. E. Lowther, and J. Goss

Appl. Phys. Lett. 69, 2489 (1996); http://dx.doi.org/10.1063/1.117715 (3 pages) | Cited 32 times

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In spite of large concentrations of phosphorus being incorporated into diamond, the material often remains insulating. It is argued that this occurs through the formation of phosphorus‐vacancy complexes which are deep acceptors and compensate any donor. The complex is analyzed using a first‐principles cluster method. In the ionized state, the defect is diamagnetic and cannot give rise to any internal optical transitions although broad band donor–acceptor transitions are expected—and observed—in material codoped with nitrogen. © 1996 American Institute of Physics.
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61.72.Bb Theories and models of crystal defects
71.55.Cn Elemental semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Small atom diffusion and breakdown of the Stokes–Einstein relation in the supercooled liquid state of the Zr46.7Ti8.3Cu7.5Ni10Be27.5 alloy

U. Geyer, W. L. Johnson, S. Schneider, Y. Qiu, T. A. Tombrello, and M.‐P. Macht

Appl. Phys. Lett. 69, 2492 (1996); http://dx.doi.org/10.1063/1.117716 (3 pages) | Cited 35 times

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Be diffusivity data in the bulk metallic glass forming alloy Zr46.7Ti8.3Cu7.5Ni10Be27.5 are reported for temperatures between 530 and 710 K, extending 85 K into the supercooled liquid state of the alloy. At the glass transition temperature Tg, a change in temperature dependence of the data is observed, and above Tg the diffusivity increases more quickly with temperature than below. The data in the supercooled liquid can be described by a modified Arrhenius expression based on a diffusion mechanism suggested earlier. The comparison with viscosity data in the supercooled liquid state of Zr46.7Ti8.3Cu7.5Ni10Be27.5 reveals a breakdown of the Stokes–Einstein relation, indicating a cooperative diffusion mechanism in the supercooled liquid state of Zr46.7Ti8.3Cu7.5Ni10Be27.5. © 1996 American Institute of Physics.
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66.30.Fq Self-diffusion in metals, semimetals, and alloys
66.10.C- Diffusion and thermal diffusion
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Simultaneous determination of the strain/stress tensor and the unstrained lattice constants by x‐ray diffraction

Thomas Wieder

Appl. Phys. Lett. 69, 2495 (1996); http://dx.doi.org/10.1063/1.117717 (3 pages)

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The main prerequisite for residual stress evaluation by x‐ray diffraction is the knowledge of the unstrained lattice constants a0,m (m=1,2,3). Often the a0,m are unknown. A method is presented which gives the stress and strain tensor together with the a0,m simultaneously from the same set of data. © 1996 American Institute of Physics.
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61.05.C- X-ray diffraction and scattering
68.60.Bs Mechanical and acoustical properties
62.20.-x Mechanical properties of solids

Non‐Markovian gain of a quantum‐well laser with many‐body effects

Doyeol Ahn

Appl. Phys. Lett. 69, 2498 (1996); http://dx.doi.org/10.1063/1.117719 (3 pages) | Cited 4 times

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The optical gain of a quantum‐well laser is studied taking into account the valence‐band mixing, non‐Markovian relaxation, and the many‐body effects. Plasma screening and excitonic effects are taken into account in the time‐dependent Hartree–Fock approximation. Conventional gain spectra calculated with the Lorentzian line shape function show two erroneous phenomena: unnatural absorption region below the band‐gap energy and mismatch of the transparency point in the gain spectra with the Fermi‐level separation, the latter suggesting that the carriers and the photons are not in thermal (or quasi) equilibrium. It is shown that the non‐Markovian gain model with many‐body effects removes the two errors associated with the Lorentzian line shape function with the proper choice of the correlation time. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

A magneto‐photoluminescence investigation of the band offset between InAs and arsenic‐rich InAs1−xSbx alloys

P. J. P. Tang, M. J. Pullin, Y. B. Li, C. C. Phillips, R. A. Stradling, S. J. Chung, W. T. Yuen, L. Hart, D. J. Bain, and I. Galbraith

Appl. Phys. Lett. 69, 2501 (1996); http://dx.doi.org/10.1063/1.117720 (3 pages) | Cited 10 times

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InAs/InAs0.865Sb0.135 quantum wells are characterized using magneto‐photoluminescence. Band‐ to‐band transitions are found at energies lower than the band gaps of either the InAs or the InAs0.865Sb0.135 with photoluminescence emission at wavelengths up to 4.8 μm. By modeling the quantum size shifts of the photoluminescence transitions and their energy shift in a magnetic field, the valence band offset between InAs and In(As,Sb) is deduced to be type II with electron confinement in the In(As,Sb) alloy and hole confinement in InAs. © 1996 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

Strain effects on valence band structure in würtzite GaN quantum wells

Yu. M. Sirenko, J.‐B. Jeon, K. W. Kim, M. A. Littlejohn, and M. A. Stroscio

Appl. Phys. Lett. 69, 2504 (1996); http://dx.doi.org/10.1063/1.117721 (3 pages) | Cited 23 times

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The effect of strain on valence band spectra in both bulk and in pseudomorphic GaN quantum wells is studied theoretically using recent experimental results for deformation potential constants. Wave functions and dispersion curves for A‐, B‐ and C‐hole subbands are obtained from linear combination of bulk analytical solutions for the 3×3 würtzite block‐Hamiltonian. A detailed analysis is presented for the dependence of hole spectrum on quantum well width, depth, and strain due to lattice mismatch.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
71.10.Pm Fermions in reduced dimensions (anyons, composite fermions, Luttinger liquid, etc.)
71.20.Nr Semiconductor compounds

Monitoring surface stoichiometry with the (2×2) reconstruction during growth of hexagonal‐phase GaN by molecular beam epitaxy

P. Hacke, G. Feuillet, H. Okumura, and S. Yoshida

Appl. Phys. Lett. 69, 2507 (1996); http://dx.doi.org/10.1063/1.117722 (3 pages) | Cited 62 times

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Reflection high‐energy electron diffraction is used to study the stability of the (2×2) reconstruction on the (0001) surface of hexagonal‐phase GaN as a function of growth parameters. The relationship between the critical conditions for existence of the reconstruction, which corresponds to a unique surface stoichiometry, is used to show the interdependency and scalability of growth parameters. A model is proposed to describe the stoichiometric balance of the species arriving on the surface at the critical conditions for observation of the reconstruction. Hall mobility of the GaN epitaxial layers was improved by growing under these conditions. © 1996 American Institute of Physics.
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68.35.Rh Phase transitions and critical phenomena
68.60.Dv Thermal stability; thermal effects
61.66.Bi Elemental solids
61.66.Dk Alloys
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Contactless determination of current–voltage characteristics and minority‐carrier lifetimes in semiconductors from quasi‐steady‐state photoconductance data

Ronald A. Sinton and Andres Cuevas

Appl. Phys. Lett. 69, 2510 (1996); http://dx.doi.org/10.1063/1.117723 (3 pages) | Cited 329 times

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A simple method for implementing the steady‐state photoconductance technique for determining the minority‐carrier lifetime of semiconductor materials is presented. Using a contactless instrument, the photoconductance is measured in a quasi‐steady‐state mode during a long, slow varying light pulse. This permits the use of simple electronics and light sources. Despite its simplicity, the technique is capable of determining very low minority carrier lifetimes and is applicable to a wide range of semiconductor materials. In addition, by analyzing this quasi‐steady‐state photoconductance as a function of incident light intensity, implicit current–voltage characteristic curves can be obtained for noncontacted silicon wafers and solar cell precursors in an expedient manner. © 1996 American Institute of Physics.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Pz Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Thick AlxGa1−xAs: An intrinsically percolating barrier owing to its microscopic structural inhomogeneity

D. S. Kim, H. S. Ko, Y. M. Kim, S. J. Rhee, S. C. Hong, Y. H. Yee, D. S. Yee, J. C. Woo, H. J. Choi, J. Ihm, D. H. Woo, and K. N. Kang

Appl. Phys. Lett. 69, 2513 (1996); http://dx.doi.org/10.1063/1.117724 (3 pages) | Cited 2 times

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A significant charge transfer, which differs from tunneling, over thick AlxGa1−xAs barrier in GaAs/AlxGa1−xAs asymmetric double quantum wells is studied by cw photoluminescence excitation (PLE) and time‐resolved photoluminescence. It is found that 300‐Å‐thick Al0.3Ga0.7As barrier is universally ‘‘leaky’’ with transport time of ∼300 ps, while AlAs and AlAs/GaAs digital alloy barriers with same thickness are not. Aided by a model calculation, we suggest that the intrinsic inhomogeneities in the alloy, which recent x‐ray and scanning tunneling microscope studies revealed, may be responsible. © 1996 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.55.Cr III-V semiconductors
71.35.-y Excitons and related phenomena

Evaluation of molecular beam epitaxially grown AlGaAs/GaAs heterojunctions for bipolar transistor with InGaAs emitter contact layer

Shigekazu Izumi, Masayuki Sakai, Teruyuki Shimura, Norio Hayafuji, Kazuhiko Sato, and Mutsuyuki Otsubo

Appl. Phys. Lett. 69, 2516 (1996); http://dx.doi.org/10.1063/1.117725 (3 pages)

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Molecular beam epitaxially grown AlGaAs/GaAs heterojunctions were characterized by isothermal capacitance transient spectroscopy to study the performance of bipolar transistors with lattice‐mismatched InGaAs emitter contact layer. A deep level around 0.48 eV is found to be a recombination center in the N‐AlGaAs/p+‐GaAs junction which might be induced by oxygen. Anomalous signals are also observed under an isothermal condition where the edge of the depletion layer reaches the graded InGaAs/AlGaAs heterointerface. Two electron traps with activation energies of 0.26 and 0.62 eV are identified as dominant factors. © 1996 American Institute of Physics.
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71.55.Eq III-V semiconductors
85.30.Pq Bipolar transistors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Aluminum‐doped n‐type ZnSTe alloy grown by molecular beam epitaxy

I. K. Sou, Z. Yang, J. Mao, Z. H. Ma, K. W. Tong, P. Yu, and G. K. L. Wong

Appl. Phys. Lett. 69, 2519 (1996); http://dx.doi.org/10.1063/1.117718 (3 pages) | Cited 11 times

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Successful n‐type doping of ZnSTe alloy using elemental aluminum source has been carried out by molecular beam epitaxy. Hall effect measurement (300–77 K) was performed on as‐grown ZnS0.977Te0.023 epilayers with various dopant concentrations. Electron carrier concentration as high as 1.3×1019 cm−3 has been achieved. For carrier concentration higher than 5×1018 cm−3, the carrier concentration is independent of temperature, possibly indicating formation of a very shallow donor level. A group of ZnS1−xTex epilayers with different x values was doped using a constant aluminum beam flux for studying the dependence of the dopant activation on Te composition. Good activation of Al dopant was obtained for x value from 0 to a few percent, but it became poor for larger x value and finally Al became inactive for x values higher than 10%. Room temperature photoluminescence measurements on doped and undoped ZnS and ZnS1−xTex layers indicate that Al dopants form deep‐level radiative centers in addition to a shallow donor level. The characteristics of these deep levels as a function of Te composition have also been studied. © 1996 American Institute of Physics.
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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
78.55.Et II-VI semiconductors

Noncontact measurement of transport properties of long‐bulk‐carrier‐lifetime Si wafers using photothermal radiometry

Alex Salnick, Andreas Mandelis, and Claude Jean

Appl. Phys. Lett. 69, 2522 (1996); http://dx.doi.org/10.1063/1.117726 (3 pages) | Cited 19 times

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A theoretical model for the photothermal radiometric signal from semiconductors of finite thickness has been used to measure simultaneously the carrier diffusion coefficient, carrier lifetime, and surface recombination velocity of FZ Si wafers with very long bulk carrier lifetimes (industrial microelectronic grade). The results showed the importance of accounting for the finite thickness of the substrate in obtaining accurate measurements of these parameters using the entirely noncontacting radiometric approach. © 1996 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Deep‐level defects and n‐type‐carrier concentration in nitrogen implanted GaN

D. Haase, M. Schmid, W. Kürner, A. Dörnen, V. Härle, F. Scholz, M. Burkard, and H. Schweizer

Appl. Phys. Lett. 69, 2525 (1996); http://dx.doi.org/10.1063/1.117727 (3 pages) | Cited 55 times

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We analyzed the intrinsic defects and the n‐type‐carrier concentration generated by nitrogen ion implantation in n‐type GaN by deep‐level‐transient spectroscopy and by capacitance–voltage measurements, respectively. The samples were grown on sapphire by metalorganic vapor‐phase epitaxy. Nitrogen implantation with different ion doses and postimplantation rapid‐thermal annealing (RTA) were investigated. We observed a growing n‐type‐carrier concentration and increasing defect concentration with increasing nitrogen ion implantation doses. After RTA the concentration of free carriers and deep levels as found in the as‐grown state are restored. We also address contrarily seeming results from measurements of sheet resistance after N implantation published recently. © 1996 American Institute of Physics.
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61.72.J- Point defects and defect clusters
61.72.uj III-V and II-VI semiconductors
71.55.Eq III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
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