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1 Feb 1999

Volume 74, Issue 5, pp. 635-772

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High-quality ultrathin gate oxide prepared by oxidation in D2O

Hyojune Kim and Hyunsang Hwang

Appl. Phys. Lett. 74, 709 (1999); http://dx.doi.org/10.1063/1.122994 (2 pages) | Cited 13 times

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In this letter, we present a process to incorporate deuterium at the Si/SiO2 interface using deuterium oxide (D2O) as an oxidizing gas. We have investigated the electrical and reliability characteristics of ultrathin gate oxide grown in D2O ambient. Compared with a control oxide grown in H2O, an oxide grown in D2O exhibits a significant reduction of charge trapping and interface state generation. Based on secondary ion mass spectroscopy analysis, we found a deuterium-rich layer at the Si/SiO2 interface. The improvement of electrical and reliability characteristics can be explained by the deuterium incorporation at the Si/SiO2 interface. © 1999 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.65.Mq Oxidation
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
73.20.At Surface states, band structure, electron density of states

Hot electron relaxation time in GaN

Hong Ye, G. W. Wicks, and P. M. Fauchet

Appl. Phys. Lett. 74, 711 (1999); http://dx.doi.org/10.1063/1.122995 (3 pages) | Cited 41 times

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The hot electron relaxation time is studied in an n-type GaN film grown by molecular beam epitaxy on sapphire. A femtosecond pump–probe technique is used in which the electrons are excited by an infrared pump and the carrier dynamics are monitored by a tunable near ultraviolet probe. Complex transients, showing bleaching or induced absorption, are observed. The data are fitted by a model in which the longitudinal optical (LO)-phonon emission is the dominant energy relaxation process. The LO-phonon emission time is measured to be 0.2 ps. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.40.Fy Semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.47.-p Spectroscopy of solid state dynamics
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
63.20.K- Phonon interactions

Direct electronic transport through an ensemble of InAs self-assembled quantum dots

S. K. Jung, S. W. Hwang, B. H. Choi, S. I. Kim, J. H. Park, Yong Kim, E. K. Kim, and S.-K. Min

Appl. Phys. Lett. 74, 714 (1999); http://dx.doi.org/10.1063/1.122996 (3 pages) | Cited 12 times

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Electronic transport properties through an ensemble of InAs self-assembled quantum dots are reported. A metal–semiconductor–metal diode with self-assembled quantum dots has been fabricated. Clear staircases are observed in the current–voltage characteristics measured from the diode, and several peak structures are identified in the differential conductance. These conductance peaks are interpreted as due to resonant tunneling through the energy states of the self-assembled quantum dots. © 1999 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Sx Metal-semiconductor-metal structures
73.23.Hk Coulomb blockade; single-electron tunneling

Determination of the valence-band offset for GaInAsSb/InP heterostructure

J. R. Chang, Y. K. Su, Y. T. Lu, D. H. Jaw, H. P. Shiao, and W. Lin

Appl. Phys. Lett. 74, 717 (1999); http://dx.doi.org/10.1063/1.123101 (3 pages) | Cited 3 times

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Unstrained Ga0.64In0.36As0.84Sb0.16/InP single quantum-well structures were grown on InP substrates by metalorganic vapor phase epitaxy. Transmission electron microscopy and temperature-dependent photoluminescence (PL) measurements were performed. The valence-band offset of the GaInAsSb/InP heterojunction was estimated by the dependence of PL peak energy on the well width at 8 K. We estimated the valence-band offset to be 70±5% of the band-gap difference for the Ga0.64In0.36As0.84Sb0.16/InP heterostructure. © 1999 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors

Characterization of the inverted Ga0.52In0.48P/GaAs (001) junctions using current–voltage and capacitance–voltage measurements

C. Cai, M. I. Nathan, and T. H. Lim

Appl. Phys. Lett. 74, 720 (1999); http://dx.doi.org/10.1063/1.123102 (3 pages) | Cited 7 times

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Al/u:GaAs/n:Ga0.52In0.48P inverted-structure (GaAs on top) Schottky diodes on n+ GaAs (001) substrates have been grown by gas source molecular beam epitaxy with several GaAs thicknesses from 10 to 100 nm. The barrier height determined by the capacitance versus voltage method is substantially higher than the barrier height determined by the current versus voltage method. These results suggest that there is a negative interface charge 6–8×1011/cm−2 at the GaAs/Ga0.52In0.48P interface, which is opposite in sign to the interface charge at the normal structure of the Ga0.52In0.48P/GaAs heterojunction reported previously. © 1999 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Kk Junction diodes
73.20.-r Electron states at surfaces and interfaces
73.30.+y Surface double layers, Schottky barriers, and work functions
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Spatiotemporal correlation of conduction current fluctuations within a hydrodynamic-Langevin scheme

P. Shiktorov, E. Starikov, V. Gružinskis, T. González, J. Mateos, D. Pardo, L. Reggiani, L. Varani, J. C. Vaissiere, and J. P. Nougier

Appl. Phys. Lett. 74, 723 (1999); http://dx.doi.org/10.1063/1.123103 (3 pages) | Cited 2 times

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We present a hydrodynamic-Langevin scheme to describe electronic noise in unipolar structures and evaluate the cross-correlation functions of conduction current fluctuations entering the transfer impedance method. The theory is developed in terms of microscopic fluctuations of carrier velocity and energy taking place during scattering events. Applications to submicron n+nn+ GaAs structures show that the contribution of stochastic velocity rate prevails over that of the energy rate in determining the cross-correlation function of conduction current fluctuations. © 1999 American Institute of Physics.
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85.30.De Semiconductor-device characterization, design, and modeling
73.50.Td Noise processes and phenomena

Observation of local tilted regions in strain-relaxed SiGe/Si buffer layers using x-ray microdiffraction

P. M. Mooney, J. L. Jordan-Sweet, I. C. Noyan, S. K. Kaldor, and P.-C. Wang

Appl. Phys. Lett. 74, 726 (1999); http://dx.doi.org/10.1063/1.123104 (3 pages) | Cited 13 times

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The microstructure of strain-relaxed Si1−xGex/Si films that relaxed by different dislocation nucleation mechanisms has been investigated using x-ray microdiffraction with a diffracted beam footprint of 1 μm×5μm. Intensity variations in the x-ray microtopographs of samples having step-graded intermediate layers, which relaxed by dislocation multiplication, are due to the presence of local tilted regions which are larger in area than the diffracted x-ray beam. In contrast, microtopographs of uniform composition layers, which relaxed by surface roughening and subsequent random dislocation nucleation, show little intensity contrast as the local tilted regions in these samples are much smaller than the diffracted x-ray beam. The difference in microstructure arises from the different distributions of 60 ° misfit dislocations in these two types of samples. © 1999 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.60.Bs Mechanical and acoustical properties
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Dd Experimental determination of defects by diffraction and scattering

InGaAsN solar cells with 1.0 eV band gap, lattice matched to GaAs

Steven R. Kurtz, A. A. Allerman, E. D. Jones, J. M. Gee, J. J. Banas, and B. E. Hammons

Appl. Phys. Lett. 74, 729 (1999); http://dx.doi.org/10.1063/1.123105 (3 pages) | Cited 228 times

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The design, growth by metalorganic chemical vapor deposition, and processing of an In0.07Ga0.93As0.98N0.02 solar cell, with 1.0 eV band gap, lattice matched to GaAs is described. The hole diffusion length in annealed, n-type InGaAsN is 0.6–0.8 μm, and solar cell internal quantum efficiencies >70% are obtained. Optical studies indicate that defects or impurities, from InGaAsN doping and nitrogen incorporation, limit solar cell performance. © 1999 American Institute of Physics.
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84.60.Jt Photoelectric conversion
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.30.Fs III-V and II-VI semiconductors

Control of silica cap properties by oxygen plasma treatment for single-cap selective impurity free vacancy disordering

A. Saher Helmy, S. K. Murad, A. C. Bryce, J. S. Aitchison, J. H. Marsh, S. E. Hicks, and C. D. W. Wilkinson

Appl. Phys. Lett. 74, 732 (1999); http://dx.doi.org/10.1063/1.123106 (3 pages) | Cited 17 times

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By exposing the SiO2 films used as annealing caps in the process of impurity free vacancy disordering (IFVD) to an oxygen plasma, which is produced in a reactive ion etching machine, the effect of the exposed caps on quantum well intermixing can be substantially controlled. The effect of the oxygen treatment is manifested in inhibiting the Ga outdiffusion from GaAs/AlGaAs heterostructures. A selective IFVD process using identical silica caps has been obtained by selective exposure of the caps to oxygen plasma. Differential band gap shifts in excess of 100 meV were achieved with control samples exhibiting band gap shifts less than 10 meV. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.65.Cf Surface cleaning, etching, patterning
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
66.30.Ny Chemical interdiffusion; diffusion barriers
61.72.J- Point defects and defect clusters
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Optically induced bistability in the mobility of a two-dimensional electron gas coupled to a layer of quantum dots

A. J. Shields, M. P. O’Sullivan, I. Farrer, D. A. Ritchie, K. Cooper, C. L. Foden, and M. Pepper

Appl. Phys. Lett. 74, 735 (1999); http://dx.doi.org/10.1063/1.123107 (3 pages) | Cited 37 times

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We report a bistability in the resistance of a GaAs/AlGaAs modulation doped field effect transistor in which a layer of InAs self-organized quantum dots has been grown near the electron channel. Brief optical illumination causes a large, persistent drop in the two-dimensional electron gas (2DEG) resistance which can be recovered by allowing a current to flow through the Schottky gate. We demonstrate that illumination reduces the number of electrons trapped in the quantum dots, lowering their potential and thereby enhancing the 2DEG mobility. This bistability could be the basis of an optical memory or sensitive phototransistor. © 1999 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.50.Dn Low-field transport and mobility; piezoresistance
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
85.30.Tv Field effect devices
85.60.Dw Photodiodes; phototransistors; photoresistors
42.79.Vb Optical storage systems, optical disks

Formation of n–p–n structure on an insulating SrTiO3 single crystal using excimer laser irradiation

Jong-Won Yoon and Masaru Miyayama

Appl. Phys. Lett. 74, 738 (1999); http://dx.doi.org/10.1063/1.123108 (3 pages) | Cited 2 times

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An n–p–n semiconducting structure, similar to a p-type grain boundary between n-type grains in ceramics, was realized on an insulating SrTiO3 single crystal by using CuO diffusion and KrF excimer laser irradiation. P- and n-type semiconductivity was confirmed by Hall coefficient measurements for the laser-irradiated surface with and without CuO diffusion, respectively. Laser irradiation on the surface including a CuO-diffused line (1 μm width) gave an n–p–n structure, which showed nonlinear I–V characteristics with a nonlinear coefficient of 7. The present fabrication process is suggested to be effective for developing new oxide microelectronic devices as well as for fundamental study on grain-boundary functions of semiconducting ceramics. © 1999 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
66.30.J- Diffusion of impurities
61.72.Mm Grain and twin boundaries
72.20.My Galvanomagnetic and other magnetotransport effects
61.72.up Other materials
72.20.Ht High-field and nonlinear effects

Diffusion lengths of excited carriers in CdxZn1−xSe quantum wells

L.-L. Chao, G. S. Cargill, E. Snoeks, T. Marshall, J. Petruzzello, and M. Pashley

Appl. Phys. Lett. 74, 741 (1999); http://dx.doi.org/10.1063/1.123109 (3 pages) | Cited 10 times

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Diffusion lengths of excited carriers in a CdxZn1−xSe multiple quantum well structure were determined for temperatures between room temperature and 8 K from cathodoluminescence measurements. The diffusion length was found to depend upon temperature and Cd concentration of the quantum well. For the highest Cd concentration (x = 0.43), the diffusion length increased with temperature up to 225 K and then dropped at higher temperatures. Diffusion lengths were 0.21 μm at 8 K, 0.38 μm at 225 K, and 0.24 μm at room temperature. For the well with least Cd concentration (x = 0.24), longer diffusion lengths were obtained. The nature of the diffusing carriers is also discussed. © 1999 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Hf II-VI semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Nonuniform carrier distribution in asymmetric multiple-quantum-well InGaAsP laser structures with different numbers of quantum wells

Michael J. Hamp, Daniel T. Cassidy, B. J. Robinson, Q. C. Zhao, and D. A. Thompson

Appl. Phys. Lett. 74, 744 (1999); http://dx.doi.org/10.1063/1.123110 (3 pages) | Cited 12 times

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A method for quantifying the degree to which the uneven carrier distribution affects the operation of multiple quantum well (MQW) lasers is developed by comparing the net gains of wells in mirror image asymmetric MQW structures. The uneven carrier distribution is found to affect the performance of devices with as few as two quantum wells and decreases the net gain for wells on the n side of a ten quantum well structure by more than a factor of two. © 1999 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.)
73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
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Pseudo-Hall effect in spin-valve multilayers

Guohong Li, Zhengqi Lu, Chunlin Chai, Hongwei Jiang, and Wuyan Lai

Appl. Phys. Lett. 74, 747 (1999); http://dx.doi.org/10.1063/1.123111 (3 pages) | Cited 9 times

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Magnetoresistance and the pseudo-Hall effect in NiFe/Cu/NiFe/FeMn spin-valve multilayers were measured simultaneously in fields rotating in the film plane. Large pseudo-Hall voltages have been observed when the magnetization of the free layer was perpendicular to the sensing current, which was applied along the magnetization of the pinned layer. The pseudo-Hall voltages cannot be explained by treating the anisotropic magnetoresistance of the two permalloy layers independently. Such a cross effect of the free and pinned layers on the anisotropic magnetoresistance is dependent upon the angle between their magnetization. © 1999 American Institute of Physics.
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75.47.De Giant magnetoresistance
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.50.Ss Magnetic recording materials
73.61.At Metal and metallic alloys

Microwave characterization of Nd0.67Sr0.33MnO3−x thin films for magnetically tunable filters

J. Wosik, L.-M. Xie, M. Strikovski, J. H. Miller, and P. Przyslupski

Appl. Phys. Lett. 74, 750 (1999); http://dx.doi.org/10.1063/1.123191 (3 pages) | Cited 15 times

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We report on the microwave properties of Nd0.67Sr0.33MnO3−x (NSMO) and NSMO/YBa2Cu3O7−x thin film heterostructures. The quality factor (Q) and center frequency of a 13 GHz shielded dielectric cavity resonator, with the film comprising one surface, were measured as functions of temperature and direct current magnetic field. The Q versus field data was theoretically simulated using the Landau–Lifschitz–Gilbert dynamic permeability equation thus demonstrating that the microwave losses are determined by the ferromagnetic properties of the films. Our results indicate that the field-dependent permeability μ(B) of NSMO films holds the potential to create magnetically tunable microwave devices. © 1999 American Institute of Physics.
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84.30.Vn Filters
84.40.Az Waveguides, transmission lines, striplines
84.40.Dc Microwave circuits
75.50.Dd Nonmetallic ferromagnetic materials

Unusual power dependence of two-tone intermodulation in high-Tc superconducting microwave resonators

Balam A. Willemsen, K. E. Kihlstrom, and T. Dahm

Appl. Phys. Lett. 74, 753 (1999); http://dx.doi.org/10.1063/1.123112 (3 pages) | Cited 29 times

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We study the power dependence of two-tone intermodulation arising in high-Tc superconducting microwave resonators as a function of each tone separately. In the regime where the intermodulation power varies as the square of the input power for equally strong tones, we observe unexpected behavior of the power dependence on the individual tones. We show that this behavior can be understood in terms of a nonlinear inductance which varies linearly with the magnitude of the input current. These findings provide a consistent phenomenological picture of the unusual power dependence and should place constraints on a microscopic description of nonlinear behavior in high-Tc films where the intermodulation products vary like the square of the input power. © 1999 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
85.25.-j Superconducting devices
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.N- Response to electromagnetic fields
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Rhombohedral superlattice structure and relaxor ferroelectric behavior of (Pb0.70Ba0.30)ZrO3 ceramics

Bhadra P. Pokharel, Rajeev Ranjan, Dhananjai Pandey, V. Siruguri, and S. K. Paranjpe

Appl. Phys. Lett. 74, 756 (1999); http://dx.doi.org/10.1063/1.123113 (3 pages) | Cited 15 times

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Superlattice reflections observed in the neutron powder-diffraction patterns of (Pb0.80Ba0.20)ZrO3 (PBZ20) and (Pb0.70Ba0.30)ZrO3 (PBZ30) are explained in terms of doubled rhombohedral cell (R3c). A Rietveld analysis of the neutron data reveals that the displacements of Pb2+/Ba2+ and Zr4+ decrease with increasing Ba2+ content while the thermal parameter for Pb2+/Ba2+ increases and becomes similar to ferroelectric relaxors. Dielectric studies indeed confirm relaxor behavior in PBZ30 with Vogel–Fulcher type relaxational freezing. © 1999 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Gm Dielectric loss and relaxation
61.66.Fn Inorganic compounds
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
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Quantum grid infrared photodetectors

L. P. Rokhinson, C. J. Chen, D. C. Tsui, G. A. Vawter, and K. K. Choi

Appl. Phys. Lett. 74, 759 (1999); http://dx.doi.org/10.1063/1.123302 (3 pages) | Cited 5 times

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In this letter we introduce a quantum well infrared photodetector (QWIP) structure, which we refer to as the quantum grid infrared photodetector (QGIP). In an ideal structure, a grid pattern with very narrow linewidth is created in the QWIP active region to achieve lateral electron confinement, thereby improving its absorption as well as transport characteristics. In order to realize this detector structure, we have fabricated QGIPs with line patterns of lithographical linewidths wl ranging from 0.1 to 4 μm, allowing for possible sidewall depletion. Low-damage reactive ion beam etching was employed to produce vertical sidewalls. From the experimental data, although the best detector performance occurs at wl ≈ 1.5 μm, the detector starts to improve when wl<0.5 μm, indicating a possible quantum confinement effect. © 1999 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.65.Cf Surface cleaning, etching, patterning

High-speed, low-noise metal–semiconductor–metal ultraviolet photodetectors based on GaN

D. Walker, E. Monroy, P. Kung, J. Wu, M. Hamilton, F. J. Sanchez, J. Diaz, and M. Razeghi

Appl. Phys. Lett. 74, 762 (1999); http://dx.doi.org/10.1063/1.123303 (3 pages) | Cited 66 times

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We present the fabrication and characterization of nonintentionally doped GaN and GaN:Mg Schottky metal–semiconductor–metal (MSM) photodetectors, grown on sapphire by metalorganic chemical vapor deposition. Low-leakage, Schottky contacts were made with Pt/Au. The devices are visible blind, with an ultraviolet/green contrast of about five orders of magnitude. The response times of the MSM devices were <10 ns and about 200 ns for GaN and GaN:Mg, respectively. The noise power spectral density remains below the background level of the system (10−24 A2/Hz) up to 5 V, for the undoped GaN MSM detector. © 1999 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
06.60.Jn High-speed techniques (microsecond to femtosecond)
78.66.Fd III-V semiconductors
78.40.Fy Semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors

An AlAs/InGaAs/AlAs/InAlAs double-barrier quantum well infrared photodetector operating at 3.4 μm and 205 K

Jung Hee Lee, Jung-Chi Chiang, Sheng S. Li, and P. J. Kannam

Appl. Phys. Lett. 74, 765 (1999); http://dx.doi.org/10.1063/1.123304 (3 pages) | Cited 8 times

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A high-performance n-type AlAs/InGaAs/AlAs/InAlAs double-barrier quantum well infrared photodetector grown on InP with photovoltaic (PV) and photoconductive (PC) dual-mode operation has been fabricated and characterized in this work. The PV and PC detection scheme employs the intersubband transition from the ground bound state to the quasibound excited state in the double-barrier well. The peak responsivities for the PV mode at zero bias and PC mode at Vb = −3 V were found to be 19 and 159 mA/W at λp = 3.4 μm and T = 77 K, respectively. The corresponding background limited performance (BLIP) detectivity (DBLIP∗) was given by 8.9×1010 cm Hz1/2/W for the PV mode and non-BLIP D∗ = 5.36×1010 cm Hz1/2/W for the PC mode. This device is capable of operating up to 205 K with good performance characteristics. © 1999 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
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
72.40.+w Photoconduction and photovoltaic effects

Ballistic transport of electrons in T-shaped quantum waveguides

P. Debray, O. E. Raichev, M. Rahman, R. Akis, and W. C. Mitchel

Appl. Phys. Lett. 74, 768 (1999); http://dx.doi.org/10.1063/1.123305 (3 pages) | Cited 7 times

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Ballistic transport of electrons through T-shaped quantum waveguides with stubs of small lithographic area (0.075 μm2) has been studied. Measurements of the conductance G at 90 mK as a function of the top gate voltage, which changes the stub height, show well-defined, almost periodic oscillations in G. A theoretical analysis, involving estimation of the shape and size of the device under gate biases and computation of the transmission probabilities from numerical analysis of the Schrödinger equation, successfully explains the main features of the experimental observations. The observed minima in G can be attributed to reflection resonances of electron waves from the resonant states of the stub cavity. This work establishes the potential of electron stub tuners in microelectronics applications. © 1999 American Institute of Physics.
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73.23.Ad Ballistic transport
85.35.Ds Quantum interference devices
73.50.Fq High-field and nonlinear effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
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Nonparametric characterization of human breast tissue by the Laguerre expansion of the kernels technique applied on propagating femtosecond laser pulses through biopsy samples

Giannis Zacharakis, Aggeliki Zolindaki, Vangelis Sakkalis, George Filippidis, Eugenios Koumantakis, and Theodore G. Papazoglou

Appl. Phys. Lett. 74, 771 (1999); http://dx.doi.org/10.1063/1.123306 (2 pages) | Cited 1 time

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Ultrafast laser pulses transmitted through excised human breast tissue have been detected by a streak camera. Experimental data of the temporal spread of the ultrafast pulse during the transmission through the tissue have been analyzed using the Laguerre expansion technique. This method treats the medium of propagation as a “black box system” and using data sets of incident–transmitted pulse, it relates to this system a set of coefficients as well the first-order system kernels. This analysis could present an alternative method of tissue characterization when, due to the limited optical thickness of small biopsy samples, the photon diffusion approximation cannot be used successfully. © 1999 American Institute of Physics.
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87.63.L- Visual imaging
42.62.Be Biological and medical applications
07.68.+m Photography, photographic instruments; xerography
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