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3 May 2004

Volume 84, Issue 18, pp. 3435-3703

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 3648 (2004); http://dx.doi.org/10.1063/1.1737470 (3 pages)

Jingbo Li and Lin-Wang Wang
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20 μm cutoff heterojunction interfacial work function internal photoemission detectors

S. G. Matsik, M. B. M. Rinzan, D. G. Esaev, A. G. U. Perera, H. C. Liu, and M. Buchanan

Appl. Phys. Lett. 84, 3435 (2004); http://dx.doi.org/10.1063/1.1634386 (3 pages) | Cited 6 times

Online Publication Date: 20 April 2004

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Results are reported on Heterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) detectors designed for operation up to 20 μm. The peak response of 100 mA/W at 12.5 μm with a D∗ of 2×1011 Jones was observed with a cutoff wavelength of ∼20 μm. The BLIP temperature for the devices was 40 K at 1.5 V bias. While the peak response remained almost constant (∼95 mA/W) up to 40 K, the D∗ reduced to 5×109 Jones due to the increased dark current. The response increased with doping while the dark current did not change significantly. Hence, higher responsivity and D∗ can be expected for designs with higher doping. Designs utilizing increased reflection from the bottom contact are suggested to improve the resonant cavity enhancement for optimizing the detectors, which should lead to higher D∗ and BLIP temperature. © 2004 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
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Pz Photoconduction and photovoltaic effects
61.72.uj III-V and II-VI semiconductors

p-type behavior in phosphorus-doped (Zn,Mg)O device structures

Y. W. Heo, Y. W. Kwon, Y. Li, S. J. Pearton, and D. P. Norton

Appl. Phys. Lett. 84, 3474 (2004); http://dx.doi.org/10.1063/1.1737795 (3 pages) | Cited 114 times

Online Publication Date: 20 April 2004

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The characteristics of device structures that employ phosphorus-doped (Zn,Mg)O have been examined in a effort to delineate the carrier type behavior in this material. The capacitance–voltage properties of metal/insulator/P-doped (Zn,Mg)O diode structures were measured and found to exhibit a polarity consistent with the P-doped (Zn,Mg)O layer being p type. In addition, thin-film junctions comprising n-type ZnO and P-doped (Zn,Mg)O display asymmetric I–V characteristics that are consistent with the formation of a p–n junction at the interface. Although Hall measurements of the P-doped (Zn,Mg)O thin films yielded an indeterminate Hall sign due to a small carrier mobility, these results are consistent with previous reports that phosphorus can yield an acceptor state and p-type behavior in ZnO materials. © 2004 American Institute of Physics.
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85.30.Kk Junction diodes
61.72.uj III-V and II-VI semiconductors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Dn Low-field transport and mobility; piezoresistance

High efficiency low operating voltage polymer light-emitting diodes with aluminum cathode

X. Y. Deng, W. M. Lau, K. Y. Wong, K. H. Low, H. F. Chow, and Y. Cao

Appl. Phys. Lett. 84, 3522 (2004); http://dx.doi.org/10.1063/1.1739510 (3 pages) | Cited 43 times

Online Publication Date: 20 April 2004

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By blending poly(ethylene glycol) (PEG) into an electroluminescence (EL) polymer, significantly enhanced EL efficiency in a polymer light-emitting diode (PLED) with aluminum electrode was achieved. An orange-color-emitting PLED with 10 wt % PEG blending achieved device efficiencies exceeding 2.6 cd/A for a wide range of bias voltage, which is more than two orders of magnitude higher than that of a similar PLED without the PEG blending. The enhanced efficiency was a result of the reduction of electron injection barrier height at the cathode–polymer interface. It is believed that interfacial interaction that is specific to Al plays an important role in the enhancement mechanism. © 2004 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
42.70.Jk Polymers and organics
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Device deformation during low-frequency pulsed operation of high-power diode bars

Axel Gerhardt, Fritz Weik, Tien QuocTran, Jens W. Tomm, Thomas Elsaesser, Jens Biesenbach, Holger Müntz, Gabriele Seibold, and Mark L. Biermann

Appl. Phys. Lett. 84, 3525 (2004); http://dx.doi.org/10.1063/1.1739516 (3 pages) | Cited 6 times

Online Publication Date: 20 April 2004

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Thermal tuning rates of single emitters in “cm-bar” high-power diode laser arrays are analyzed. We find these tuning rates to consist of purely thermal and mechanical pressure contributions, of −0.48 and −0.08 meV(K)−1, respectively. We estimate the mechanical deformation such a device experiences during pulsed operation to be 0.07%, and then apply an adequate external force to single segments of cm bars. These single segments model the central emitters within the array. Effects that arise due to gradual aging, such as nonequilibrium carrier lifetime decrease, sheet carrier concentration increase, and defect concentration rise are monitored and analyzed over up to 2×106 deformation cycles. These experiments provide the basis for a type of accelerated aging experiment for device testing, especially of devices designed for low-frequency pulsed operation. © 2004 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
85.30.Kk Junction diodes

Fundamental limits to detection of low-energy ions using silicon solid-state detectors

H. O. Funsten, S. M. Ritzau, R. W. Harper, and R. Korde

Appl. Phys. Lett. 84, 3552 (2004); http://dx.doi.org/10.1063/1.1719272 (3 pages) | Cited 9 times

Online Publication Date: 20 April 2004

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Recent advances in solid-state detector (SSD) technology have demonstrated the detection of ions and electrons down to 1 keV. However, ions at keV energies lose a substantial amount of energy ΔN in a SSD through Coulombic interactions with target nuclei rather than through interactions that contribute to the SSD output pulse, whose magnitude is a measure of the ion’s incident energy. Because ΔN depends on the ion species, detector material, and interaction physics, it represents a fundamental limitation of the output pulse magnitude of the detector. Using 100% quantum collection efficiency silicon photodiodes with a thin (40–60 Å) SiO2 passivation layer, we accurately quantify ΔN for incident 1–120 keV ions and, therefore, evaluate the detection limits of keV ions using silicon detectors. © 2004 American Institute of Physics.
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29.40.Wk Solid-state detectors

Patterning-free integration of polymer light-emitting diode and polymer transistor

Z. L. Li, S. C. Yang, H. F. Meng, Y. S. Chen, Y. Z. Yang, C. H. Liu, S. F. Horng, C. S. Hsu, L. C. Chen, J. P. Hu, and R. H. Lee

Appl. Phys. Lett. 84, 3558 (2004); http://dx.doi.org/10.1063/1.1728301 (3 pages) | Cited 14 times

Online Publication Date: 20 April 2004

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We demonstrate an integration of polymer light-emitting diode (LED) and polymer transistor in which no patterning of the organic layers is needed. Intrinsic high-mobility semiconducting conjugated polymer poly(3-hexylthiophene)(P3HT) is used as the hole-transport layer for polymer LED. The light emission efficiency is only slightly lower than the LED with conventional heavily doped hole-transport layer. Such LED is easily integrated with a P3HT transistor without patterning.© 2004 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.30.Tv Field effect devices
42.70.Jk Polymers and organics
85.65.+h Molecular electronic devices

1 micron wavelength photo- and electroluminescence from a conjugated polymer

Miaoxiang Chen, Erik Perzon, Mats R. Andersson, Saulius Marcinkevicius, S. K. M. Jönsson, Mats Fahlman, and Magnus Berggren

Appl. Phys. Lett. 84, 3570 (2004); http://dx.doi.org/10.1063/1.1737064 (3 pages) | Cited 39 times

Online Publication Date: 20 April 2004

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We report photo- and electroluminescence from an alternating conjugated polymer consisting of fluorene units and low-band gap donor-acceptor-donor (D–A–D) units. The D–A–D segment includes two electron-donating thiophene rings combined with a thiadiazolo-quinoxaline unit, which is electron withdrawing to its nature. The resulting polymer is conjugated and has a band gap of 1.27 eV. The corresponding electro- and photoluminescence spectra both peak at approximately 1 μm. Light-emitting diodes, based on a single layer of the polymer, demonstrated external quantum efficiencies from 0.03% to 0.05%. © 2004 American Institute of Physics.
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78.55.Kz Solid organic materials
78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
78.55.Qr Amorphous materials; glasses and other disordered solids
42.70.Jk Polymers and organics

Highly sensitive ac nanocalorimeter for microliter-scale liquids or biological samples

J.-L. Garden, E. Château, and J. Chaussy

Appl. Phys. Lett. 84, 3597 (2004); http://dx.doi.org/10.1063/1.1737794 (3 pages) | Cited 19 times

Online Publication Date: 20 April 2004

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We developed an ultrasensitive ac nanocalorimeter for use with biological liquids by means of microfabrication technologies. The volume of the cell measurement is only 5 μL. This nanocalorimeter, tested on deionized water, allows the measurement of heat capacity variation above ±150 nJ/K (resolution of ±5×10−6) with an operating temperature ranging from −20 to 120 °C and a stability of 100 μK. Its use is demonstrated on diluted lysosyme solution measured at the frequency of 3 Hz. At 3 Hz, this ac calorimeter gives only the variation of the heat capacity during the denaturation, which allows complementary thermodynamic investigations as regards to classical differential scanning calorimetry measurements. © 2004 American Institute of Physics.
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07.20.Fw Calorimeters
87.14.E- Proteins
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
61.46.-w Structure of nanoscale materials
65.20.-w Thermal properties of liquids
61.25.H- Macromolecular and polymers solutions; polymer melts

Double-transconductance-plateau characteristics in InGaAs/GaAs real-space transfer high-electron-mobility transistor

Ching-Sung Lee and Wei-Chou Hsu

Appl. Phys. Lett. 84, 3618 (2004); http://dx.doi.org/10.1063/1.1738512 (3 pages) | Cited 4 times

Online Publication Date: 20 April 2004

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Bias-tunable double-transconductance-plateau characteristics due to real-space transfer through the lowering of conduction band offset at high electric fields in a δ-doped InGaAs/GaAs high-electron-mobility transistor have been observed. Extrinsic, unpassivated peak performance values, with gate dimensions of 1×125 μm2, include the transconductance plateaus of 269 and 116 mS/mm at VDS = 3 V for VGS = 0 V and −1.5 V, respectively, maximum drain current density of 382 mA/mm at VDS = 5.5 V, unity current gain cutoff frequency of 15.5 GHz, and maximum frequency of oscillation of 23 GHz. The present structure is promising for high-speed analog-to-digital converters or multiple-state quantizer applications. © 2004 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
84.40.-x Radiowave and microwave (including millimeter wave) technology
73.50.Dn Low-field transport and mobility; piezoresistance
73.20.At Surface states, band structure, electron density of states
71.20.Nr Semiconductor compounds

Visible light-emitting diodes using a-plane GaN–InGaN multiple quantum wells over r-plane sapphire

Ashay Chitnis, Changqing Chen, Vinod Adivarahan, Maxim Shatalov, Edmundas Kuokstis, Vasavi Mandavilli, Jinwei Yang, and M. Asif Khan

Appl. Phys. Lett. 84, 3663 (2004); http://dx.doi.org/10.1063/1.1738938 (3 pages) | Cited 96 times

Online Publication Date: 20 April 2004

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We report blue-purple pn-junction light-emitting diodes (LEDs) with a-plane GaN–InGaN multiple quantum well active region. The LEDs were grown over r-plane sapphire substrates. Our study has shown the low pump intensity photoluminencence and electroluminescence to be dominated by emission from the band-tail states which then saturates rapidly giving rise to band-edge emission. © 2004 American Institute of Physics.
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85.60.Jb Light-emitting devices
68.65.Fg Quantum wells
78.55.Cr III-V semiconductors
78.60.Fi Electroluminescence

High performance of potassium n-doped carbon nanotube field-effect transistors

M. Radosavljević, J. Appenzeller, Ph. Avouris, and J. Knoch

Appl. Phys. Lett. 84, 3693 (2004); http://dx.doi.org/10.1063/1.1737062 (3 pages) | Cited 41 times

Online Publication Date: 20 April 2004

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We describe a robust technique for the fabrication of high performance vertically scaled n-doped field-effect transistors from large band gap carbon nanotubes. These devices have a tunable threshold voltage in the technologically relevant range (−1.3 V ⩽ Vth ⩽ 0.5 V) and can carry up to 5–6 μA of current in the on-state. We achieve such performance by exposure to potassium (K) vapor and device annealing in high vacuum. The treatment has a twofold effect to: (i) controllably shift Vth toward negative gate biases via bulk doping of the nanotube (up to about 0.6e−/nm), and (ii) increase the on-current by 1–2 orders of magnitude. This current enhancement is achieved by lowering external device resistance due to more intimate contact between K metal and doped nanotube channel in addition to potential reduction of the Schottky barrier height at the contact. © 2004 American Institute of Physics.
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85.35.Kt Nanotube devices
85.30.Tv Field effect devices
61.72.Cc Kinetics of defect formation and annealing
85.40.Ry Impurity doping, diffusion and ion implantation technology
73.30.+y Surface double layers, Schottky barriers, and work functions
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