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26 Apr 1999

Volume 74, Issue 17, pp. 2405-2555

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Optical and electrical tuning of the frequency in self-oscillating multiple shallow quantum-well diodes

O-Kyun Kwon, Kyu-Seok Lee, Hye Yong Chu, El-Hang Lee, and Byung-Tae Ahn

Appl. Phys. Lett. 74, 2537 (1999); http://dx.doi.org/10.1063/1.123890 (3 pages)

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We have studied photoinduced self-oscillation characteristics in GaAs/AlGaAs multiple shallow quantum-well diodes as a function of bias voltage and laser power. Under the illumination of a laser of wavelength corresponding to the exciton absorption energy, the I–V curve of the diode revealed a large negative differential conductance region where the electrical and optical oscillations were observed in the same phase. The oscillation frequency was widely tuned by either bias voltage or laser power, and this demonstrates a large potential of the device scheme for the electrical and optical signal generators with wide frequency tunability. © 1999 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.30.Kk Junction diodes
85.30.De Semiconductor-device characterization, design, and modeling
85.60.-q Optoelectronic devices

Direct monitoring of thermally activated leakage current in AlGaInP laser diodes

S. A. Wood, P. M. Smowton, C. H. Molloy, P. Blood, D. J. Somerford, and C. C. Button

Appl. Phys. Lett. 74, 2540 (1999); http://dx.doi.org/10.1063/1.123891 (3 pages) | Cited 10 times

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Using specially prepared structures, we have observed emission from a layer of direct-gap “monitor” material placed between the p-contact layer and p-cladding layer of a conventional 670 nm GaInP laser diode at room temperature. This observation provides direct evidence for electron leakage through the p-cladding layer in these devices. Furthermore, although emission from the quantum well and waveguide core both pin above threshold, indicating that the Fermi levels clamp throughout the active region, the monitor emission continues to rise above threshold. This is characteristic of a drift component to the leakage current, which we have confirmed by a simulation of the carrier transport processes through the cladding layer with and without drift. © 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
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Optimum irradiance distribution of concentrated sunlight for photovoltaic energy conversion

Pablo Benítez and Rubén Mohedano

Appl. Phys. Lett. 74, 2543 (1999); http://dx.doi.org/10.1063/1.123892 (3 pages) | Cited 5 times

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The irradiance distribution on a concentration photovoltaic cell that produces maximum conversion efficiency has been found with the tools of Variational Calculus. The analysis is two dimensional and can be applied to a comb-like double busbar solar cell illuminated by a line-focus concentrator. The optimum distribution is, in general, nonuniform, and depends on the internal parameters of the solar cell: the higher the contribution of the grid to the global cell series resistance, the lower the uniformity of the optimum irradiance distribution. In practical cases, the efficiency for uniform illumination is close to that of the optimum, but in the latter the irradiance close to the busbar may be noticeable higher than the average. © 1999 American Institute of Physics.
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84.60.Jt Photoelectric conversion
02.30.Xx Calculus of variations
02.30.Yy Control theory

A self-assembled single-electron tunneling transistor

S. H. Magnus Persson, Linda Olofsson, and Linda Gunnarsson

Appl. Phys. Lett. 74, 2546 (1999); http://dx.doi.org/10.1063/1.123893 (3 pages) | Cited 37 times

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A single-electron tunneling transistor was made by capturing a chemically synthesized gold cluster between two gold electrodes. The transistor had a quasiperiodic modulation of the current–voltage characteristics as a function of a gate voltage applied to an oxidized aluminum electrode at 4.2 K. The Coulomb blockade voltage for this device was 50 mV observed at 4.2 K and room temperature. The maximum observed blockade voltage was 200 mV for devices without gate. © 1999 American Institute of Physics.
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85.35.Gv Single electron devices
85.65.+h Molecular electronic devices
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
73.23.Hk Coulomb blockade; single-electron tunneling
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