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20 Sep 2004

Volume 85, Issue 12, pp. 2157-2437

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Appl. Phys. Lett. 85, 2390 (2004); http://dx.doi.org/10.1063/1.1796520 (3 pages)

Stas Polonsky and Alan Weger
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Charge recombination electroluminescence in organic thin-film devices without charge injection from external electrodes

Tetsuo Tsutsui, Sang-Bong Lee, and Katsuhiko Fujita

Appl. Phys. Lett. 85, 2382 (2004); http://dx.doi.org/10.1063/1.1795367 (3 pages) | Cited 10 times

Online Publication Date: 24 September 2004

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Organic thin-film electroluminescent (EL) devices with a double-insulated structure, Al electrode/polymer insulator layer/ambipolar EL layer/ITO nanoparticles layer/ambipolar EL layer/polymer insulator layer/ITO electrode, were fabricated. The ambipolar EL layer was the composition of poly (N-vinylcarbazole) as a hole transport material and 2,5-bis(4-naphthyl)-1,3,4-oxadiazole as an electron transport material in 65∕35 molar ratio with added 0.6 mole % coumarin-6 for emissive centers. When the devices were driven with ac voltage, bright surface emission (81 cd∕m2 at 250 V and 300 kHz) was observed. Emission is due to the recombination of holes and electrons that are generated from ITO nanoparticles embedded in organic layers. Charge recombination EL is observed without charge injection from external electrodes in double-insulated organic EL devices.
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85.60.Jb Light-emitting devices
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Dn Low-field transport and mobility; piezoresistance
73.63.Bd Nanocrystalline materials

Reversible photodegradation of organic light-emitting diodes

P. Kobrin, R. Fisher, and A. Gurrola

Appl. Phys. Lett. 85, 2385 (2004); http://dx.doi.org/10.1063/1.1793344 (3 pages) | Cited 5 times

Online Publication Date: 24 September 2004

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A phenomenon in which the electroluminescence from an organic light-emitting diode is suppressed by the absorption of visible light is reported. This at-least partially reversible degradation has a recovery time measured in days at a temperature of 20 °C. The absorbed light affects both the I–V characteristics of the device and the electroluminescent quantum efficiency. The degradation is first order in exposure intensity and has been observed in red, green, and blue devices with exposure to as little as 1 W∕cm2 of green laser light.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Tunnel junctions for ohmic intra-device contacts on GaSb-substrates

Oliver Dier, Martin Sterkel, Markus Grau, Chun Lin, Christian Lauer, and Markus-Christian Amann

Appl. Phys. Lett. 85, 2388 (2004); http://dx.doi.org/10.1063/1.1793349 (2 pages) | Cited 8 times

Online Publication Date: 24 September 2004

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A tunnel junction for intradevice contacts on GaSb substrates has been realized. By using solid source molecular beam epitaxy, we have fabricated abrupt, heavily doped homo- and heterojunctions of InAs(Sb) and GaSb to form a low resistive ohmic tunnel junction. The resitivity achieved was as low as 2.6×10−5 Ω cm2.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
68.55.A- Nucleation and growth
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Off-state luminescence in metal-oxide-semiconductor field-effect transistors and its use as on-chip voltage probe

Stas Polonsky and Alan Weger

Appl. Phys. Lett. 85, 2390 (2004); http://dx.doi.org/10.1063/1.1796520 (3 pages) | Cited 1 time

Online Publication Date: 24 September 2004

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Luminescence of deep submicron metal-oxide-semiconductor field-effect transistors in the off state has been detected and characterized. It exponentially depends on voltages applied to the device and behaves similarly to its off-state leakage current. Time-resolved measurements of this luminescence allow extraction of on-chip voltages in complementary metal-oxide semiconductor integrated circuits. We propose and demonstrate the application of this technique to various signal integrity issues, such as characterization of crosstalk and power supply noise.
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85.30.Tv Field effect devices
78.47.-p Spectroscopy of solid state dynamics
78.55.Hx Other solid inorganic materials
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.30.Sk Pulse and digital circuits

Photoluminescence measurements to study conductance switching and data storage in polythiophene based devices

Chiara Botta, Clara Mercogliano, Alberto Bolognesi, Himadri S. Majumdar, and Amlan J. Pal

Appl. Phys. Lett. 85, 2393 (2004); http://dx.doi.org/10.1063/1.1794374 (3 pages) | Cited 1 time

Online Publication Date: 24 September 2004

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We have fabricated devices based on oriented thin film of a conjugated polymer, namely a polythiophene derivative, which exhibited the presence of two conducting states and switching between the states. Conductance switching in such devices has been studied by photoluminescence (PL) measurements. Depending on the conducting state of the polymer, the PL intensity of the polymer showed switching between high and low values. Both the conducting states displayed an associated memory for data-storage applications. We have shown that the induced states of the polymer, which are retained for more than 2 h, can be read by the contact-less and nondestructive PL measurement.
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78.66.Qn Polymers; organic compounds
78.55.Qr Amorphous materials; glasses and other disordered solids
72.60.+g Mixed conductivity and conductivity transitions
73.61.Ph Polymers; organic compounds

C60 thin-film transistors with low work-function metal electrodes

Masayuki Chikamatsu, Shuichi Nagamatsu, Tetsuya Taima, Yuji Yoshida, Natsuko Sakai, Harumi Yokokawa, Kazuhiro Saito, and Kiyoshi Yase

Appl. Phys. Lett. 85, 2396 (2004); http://dx.doi.org/10.1063/1.1796530 (3 pages) | Cited 16 times

Online Publication Date: 24 September 2004

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We report C60 thin-film transistor characteristics of top-contact structure with low work-function source and drain electrodes. The electron mobility of the Mg electrode device is one order of magnitude higher than that of the Ag electrode device. The depth profile obtained by using secondary-ion mass spectroscopy demonstrates that Mg atoms strongly diffuse into C60 film during Mg deposition. These findings indicate that the improved mobility is due to the reduction of the parasitic resistance under source and drain electrodes by the Mg doping effect.
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85.30.Tv Field effect devices
73.30.+y Surface double layers, Schottky barriers, and work functions
72.20.Fr Low-field transport and mobility; piezoresistance
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Suitability of epitaxial GaAs for x-ray imaging

G. C. Sun, N. Talbi, C. Verdeil, and J. C. Bourgoin

Appl. Phys. Lett. 85, 2399 (2004); http://dx.doi.org/10.1063/1.1796534 (3 pages) | Cited 3 times

Online Publication Date: 24 September 2004

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Because the rate of indirect photon-electron conversion for scintillator materials coupled with arrays of photodiodes is at least 25 times smaller than the rate of direct conversion, we examine the conditions to be fulfilled by semiconductors undergoing such direct conversion to be applied to x-ray imaging. Bulk grown materials are not well suited to this application, because large defect concentrations give rise to strongly nonuniform electronic properties. We argue that only epitaxial layers are suitable for use as imaging devices and we illustrate our argument using the case of thick epitaxial GaAs layers. Detectors made with such layers exhibit a good energy resolution, a charge collection efficiency which approaches 1, linearity over more than three orders of amplitude, no afterglow (a response time shorter than 20 μs), and no charge-induced polarization effects.
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07.85.-m X- and γ-ray instruments

Electron mobility in Ge and strained-Si channel ultrathin-body metal-oxide semi conductor field-effect transistors

Tony Low, M. F. Li, Chen Shen, Yee-Chia Yeo, Y. T. Hou, Chunxiang Zhu, Albert Chin, and D. L. Kwong

Appl. Phys. Lett. 85, 2402 (2004); http://dx.doi.org/10.1063/1.1788888 (3 pages) | Cited 7 times

Online Publication Date: 24 September 2004

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Electron mobility in strained silicon and various surface oriented germanium ultrathin-body (UTB) metal-oxide semiconductor field-effect transistors (MOSFETs) with sub-10-nm-body thickness are systematically studied. For biaxial tensile strained-Si UTB MOSFETs, strain effects offer mobility enhancement down to a body thickness of 3 nm, below which strong quantum confinement effect renders further valley splitting via application of strain redundant. For Ge channel UTB MOSFETs, electron mobility is found to be highly dependent on surface orientation. Ge〈100〉 and Ge〈110〉 surfaces have low quantization mass that leads to a lower mobility than that of Si in aggressively scaled UTB MOSFETs.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
68.47.Fg Semiconductor surfaces
73.61.Cw Elemental semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
73.25.+i Surface conductivity and carrier phenomena

Numerical simulation of tetracene light-emitting transistors: A detailed balance of exciton processes

Stijn Verlaak, David Cheyns, Maarten Debucquoy, Vladimir Arkhipov, and Paul Heremans

Appl. Phys. Lett. 85, 2405 (2004); http://dx.doi.org/10.1063/1.1792372 (3 pages) | Cited 20 times

Online Publication Date: 24 September 2004

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We assess the possibility to use an ambipolar organic light-emitting transistor structure as gain medium for an electrically pumped laser. Singlet and triplet continuity equations are solved together with Poissons and drift-diffusion equations in two dimensions. The solution allows for a detailed balance between the exciton decay, quenching and generation mechanisms. Simulations of a tetracene light-emitting transistor show that triplets are most dominant in quenching singlets. Singlet–triplet quenching can ultimately prevent pure tetracene crystals or films—when provided with a realistic optical feedback structure, to reach the threshold for stimulated emission.
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85.60.Jb Light-emitting devices
85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
78.45.+h Stimulated emission
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
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