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31 Jan 2000

Volume 76, Issue 5, pp. 523-656

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Analysis of submicron carbon nanotube field-effect transistors

Toshishige Yamada

Appl. Phys. Lett. 76, 628 (2000); http://dx.doi.org/10.1063/1.125840 (3 pages) | Cited 9 times

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A theoretical analysis of carbon nanotube based field-effect transistors fabricated by two different groups [Tans et al., Nature (London) 393, 49 (1998); Martel et al., Appl. Phys. Lett. 73, 2447 (1998)] is presented. The metal (electrode)-semiconductor (nanotube) contact influences subthreshold channel conductance versus gate voltage VG, such that the occurrence of a kink depends on the transport mechanism across this contact. Saturation in the turn-on drain current ID vs VG seen in experiments reflects the nanotube state density. Saturationless ID versus drain voltage VD indicates transport in the weak-localization regime in the absence of carrier–carrier scattering so that pinch-off cannot occur. To compensate for saturationless ID(VD) in digital applications, nanotube transistors need to be designed to maximize their transconductance. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
85.65.+h Molecular electronic devices
85.30.De Semiconductor-device characterization, design, and modeling
73.20.Fz Weak or Anderson localization

GaN microdisk light emitting diodes

S. X. Jin, J. Li, J. Z. Li, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 76, 631 (2000); http://dx.doi.org/10.1063/1.125841 (3 pages) | Cited 40 times

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Microdisk light-emitting diodes (μ-LEDs) with diameter of about 12 μm have been fabricated from InGaN/GaN quantum wells. Photolithographic patterning and inductively coupled plasma dry etching have been employed to fabricate these μ-LED devices. Device characteristics, such as the current–voltage characteristics, light output power, and electroluminescence (EL) spectra have been measured and compared with those of conventional broad-area LEDs. Our results showed that, for an identical area, the quantum efficiencies of μ-LED are enhanced over the conventional broad-area LEDs due to an enhanced current density and possibly microsize effects. The implications of our results on the design of future UV/blue microoptoelectronic devices are discussed. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

High luminescent efficiency in light-emitting polymers due to effective exciton confinement

R. G. Sun, Y. Z. Wang, D. K. Wang, Q. B. Zheng, E. M. Kyllo, T. L. Gustafson, and A. J. Epstein

Appl. Phys. Lett. 76, 634 (2000); http://dx.doi.org/10.1063/1.125842 (3 pages) | Cited 14 times

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Highly efficient light-emitting polymers have become possible by molecular engineering. Photoluminescence (PL) quantum yield above 90% in the solid state is reported for the alternating block copolymer of distyrylbenzene. We conclude that the alternate arrangement of conjugated and nonconjugated segments with surrounding side groups for chromophores effectively confine the excitons for radiative emission. The effectiveness of the exciton confinement is confirmed through the temperature independence of the PL quantum yield. The time-resolved PL decay measurement supports this model through the independence of the PL yield on temperature and emission wavelength. The synthesized copolymers have been employed for the fabrication of electroluminescent (EL) devices, demonstrating high external EL efficiency with low operation threshold. © 2000 American Institute of Physics.
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78.55.Kz Solid organic materials
71.35.-y Excitons and related phenomena
78.47.-p Spectroscopy of solid state dynamics
85.60.Jb Light-emitting devices

Multigate single-electron transistors and their application to an exclusive-OR gate

Yasuo Takahashi, Akira Fujiwara, Kenji Yamazaki, Hideo Namatsu, Kenji Kurihara, and Katsumi Murase

Appl. Phys. Lett. 76, 637 (2000); http://dx.doi.org/10.1063/1.125843 (3 pages) | Cited 35 times

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The two-input exclusive-OR (XOR) function was implemented by a multigate single-electron transistor (SET). Two types of multigate SETs operating at 40 K were fabricated on a top silicon layer of an Si-on-insulator wafer by using a special technique called pattern-dependent oxidation. Two small gate electrodes which act as the input gates were formed over the small SET island. The output current of the devices took a high level when a high voltage was applied to either of the two gates with the other gate grounded, while it took a low level when both gates were grounded or fed with a high voltage. It is striking that such an XOR function can be implemented with just one device. © 2000 American Institute of Physics.
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85.35.Gv Single electron devices
84.30.Sk Pulse and digital circuits
81.65.Mq Oxidation

Nonlinearity and electrothermal feedback of high Tc transition edge bolometers

H. Neff, A. M. N. Lima, G. S. Deep, R. C. S. Freire, E. Melcher, I. A. Khrebtov, and A. D. Tkachenko

Appl. Phys. Lett. 76, 640 (2000); http://dx.doi.org/10.1063/1.125844 (3 pages) | Cited 4 times

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The effects of electrothermal feedback on the performance of a micromachined superconducting high Tc transition edge bolometer, over a temperature range 85–95 K, have been investigated. The system behaves nonlinearly, due to the variation of the resistance-temperature coefficient β with temperature. Optimum operating points of constant current mode (CCM) and constant voltage mode (CVM) modes vary with temperature and biasing conditions. In CCM, effective response time τeff varies little with temperature. The optimum output signal of CVM occurs at approximately 3–5 K lower temperature within the tail region, where β is maximum. The biasing voltage also displays a maximum, above which the bolometric performance degrades. The CCM exhibits a comparatively limited linear dynamic range. Negative thermal feedback causes a decrease of τeff of up to 2 orders of magnitude in CVM. CCM requires precise thermal stabilization at midtransition. Noise in both modes is limited by the 1/f contribution. Maximum D∗ values are slightly higher for CVM at higher frequencies. Bolometer operation in the CVM mode requires cooling the heatsink below 77 K, but does not need accurate temperature control. © 2000 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
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