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15 Nov 1999

Volume 75, Issue 20, pp. 3051-3226

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Operation of quantum cellular automaton cells with more than two electrons

M. Girlanda, M. Governale, M. Macucci, and G. Iannaccone

Appl. Phys. Lett. 75, 3198 (1999); http://dx.doi.org/10.1063/1.125276 (3 pages) | Cited 6 times

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We present evidence that operation of quantum cellular automaton (QCA) cells with four dots is possible with an occupancy of 4N+2 electrons per cell (N being an integer). We show that interaction between cells can be described in terms of a revised formula for cell polarization, which is based only on the difference between diagonal occupancies. We validate our conjectures with full quantum simulations of QCA cells for a number of electrons varying from 2 to 6, using the configuration–interaction method. © 1999 American Institute of Physics.
Show PACS
03.67.Lx Quantum computation architectures and implementations
05.45.-a Nonlinear dynamics and chaos
73.23.-b Electronic transport in mesoscopic systems
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Effect of indirect minima carrier population on the output characteristics of AlGaInP light-emitting diodes

D. Patel, J. M. Pikal, C. S. Menoni, K. J. Thomas, F. A. Kish, and M. R. Hueschen

Appl. Phys. Lett. 75, 3201 (1999); http://dx.doi.org/10.1063/1.125277 (3 pages) | Cited 10 times

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We show that carrier transfer to the indirect X level in the confining layer is responsible for most of the substantial decrease in the efficiency of AlGaInP light-emitting diodes (LEDs) operating at short wavelengths. Carrier transfer to the confining X level was obtained by reducing the separation between the AlGaInP direct Γ minimum and the X levels by varying the Al composition in the active region and by the application of hydrostatic pressure. Carrier transfer to the confining X level appeared as an additional peak in the electroluminescence (EL) and resulted in a significant decrease of the LED efficiency. A simple model of the EL emission that takes into account carrier population in the X minima was found to be in excellent agreement with the measured EL behavior. © 1999 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
85.60.Jb Light-emitting devices

Facet temperature distribution in broad stripe high power laser diodes

Toshiro Hayakawa

Appl. Phys. Lett. 75, 3204 (1999); http://dx.doi.org/10.1063/1.125285 (3 pages) | Cited 6 times

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Facet temperature distribution has been measured for broad stripe high power lasers using reflectance modulation. Temporal evolution of the two-dimensional facet temperature distribution is directly measured. Measurements have been made for devices with various stripe widths. Devices with wider stripes show higher temperature and broader region of high temperature because the lateral heat dissipation becomes more ineffective. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
07.20.Dt Thermometers
07.60.Rd Visible and ultraviolet spectrometers
78.66.Fd III-V semiconductors

Quantum-well infrared photodetectors with digital graded superlattice barrier for long-wavelength and broadband detection

Jung-Hee Lee, Sheng S. Li, M. Z. Tidrow, W. K. Liu, and K. Bacher

Appl. Phys. Lett. 75, 3207 (1999); http://dx.doi.org/10.1063/1.125279 (3 pages) | Cited 10 times

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We report two high-performance quantum-well infrared photodetectors (QWIPs) using GaAs/AlGaAs digital graded superlattice barriers and InGaAs quantum wells for long-wavelength infrared and broadband (BB) detection. The compositionally digital graded superlattice barriers (DGSLBs) of the QWIP structures were grown using GaAs/AlGaAs digital graded superlattices to form a staircase-like composition-graded barrier layer without adjustment of the source temperature (510 °C) and the AlGaAs composition (15% Al). In the BB DGSLB QWIP, a broad spectral response from 7 to 16 μm wavelength range was obtained under positive bias condition, while a normal spectral response with peak wavelength at 11 μm was obtained under the negative bias condition. In addition, a double-barrier (DB) DGSLB QWIP structure adding a thin (20 Å) undoped Al0.15Ga0.85As on each side of the InGaAs quantum well to form a DB structure for the confinement of electron wave functions in the E4 states was also studied. A peak responsivity of 3 A/W was obtained at Vb = 1 V, T = 35 K, and λp = 12 μm, and normal spectral response was observed in this device. © 1999 American Institute of Physics.
Show PACS
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.60.Gz Photodetectors (including infrared and CCD detectors)
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