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2 Feb 2009

Volume 94, Issue 5, Articles (05xxxx)

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Appl. Phys. Lett. 94, 059901 (2009); http://dx.doi.org/10.1063/1.3086725 (3 pages)

Yuta Tsukada, Tsuyoshi Honma, and Takayuki Komatsu
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The role of electric field-induced strain in the degradation mechanism of AlGaN/GaN high-electron-mobility transistors

C. Rivera and E. Muñoz

Appl. Phys. Lett. 94, 053501 (2009); http://dx.doi.org/10.1063/1.3077190 (3 pages) | Cited 11 times

Online Publication Date: 2 February 2009

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The effect of strain induced by electric field in AlGaN/GaN high-electron-mobility transistors is investigated by theoretical calculations based on the minimization of the electric enthalpy functional. Results of the proposed model show that the converse piezoelectric effect increases (decreases) the stored elastic energy at positive gate voltage under biaxial tensile (compressive) strain, whereas it decreases (increases) at negative gate voltage. Hence, strain relaxation of piezoelectric origin is only expected in the on-state operation. In contrast, the degradation in the off-state operation could be identified with the effect of the electrostatic force generated by the increase in the stored electrostatic energy.
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85.30.Tv Field effect devices

Characteristics of polycrystalline silicon Schottky barrier thin film transistors fabricated using metallic junction source/drain with erbium silicide and platinum silicide

Jin-Wook Shin, Won-Ju Cho, Chel-Jong Choi, and Moongyu Jang

Appl. Phys. Lett. 94, 053502 (2009); http://dx.doi.org/10.1063/1.3073047 (3 pages) | Cited 1 time

Online Publication Date: 3 February 2009

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Polycrystalline silicon (poly-Si) Schottky barrier thin film transistors (SB-TFTs) were fabricated using platinum and erbium silicided source/drain for p- and n-channel SB-TFTs, respectively. High quality poly-Si films were obtained by crystallizing the amorphous Si films with the excimer laser annealing method. Poly-Si SB-TFTs with metallic source/drain junctions showed a large on/off current ratio and a low leakage current. Significant improvements in electrical characteristics were obtained by additional forming gas annealing in 2% H2/N2 gas ambient due to the termination of dangling bonds at the grain boundaries of the poly-Si film as well as the reduction in interface trap states at gate oxide/poly-Si channel.
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85.30.Tv Field effect devices
61.72.Cc Kinetics of defect formation and annealing

Optical pumping as artificial doping in quantum dots-in-a-well infrared photodetectors

L. Höglund, P. O. Holtz, H. Pettersson, C. Asplund, Q. Wang, H. Malm, S. Almqvist, E. Petrini, and J. Y. Andersson

Appl. Phys. Lett. 94, 053503 (2009); http://dx.doi.org/10.1063/1.3073048 (3 pages) | Cited 1 time

Online Publication Date: 3 February 2009

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Resonant optical pumping across the band gap was used as artificial doping in InAs/In0.15Ga0.85As/GaAs quantum dots-in-a-well infrared photodetectors. A selective increase in the electron population in the different quantum dot energy levels enabled the low temperature photocurrent peaks observed at 120 and 148 meV to be identified as intersubband transitions emanating from the quantum dot ground state and the quantum dot excited state, respectively. The response was increased by a factor of 10 through efficient filling of the quantum dot energy levels by simultaneous optical pumping into the ground states and the excited states of the quantum dots.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.65.Hb Quantum dots (patterned in quantum wells)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Atomic layer deposition of LaxZr1−xO2−δ (x = 0.25) high-k dielectrics for advanced gate stacks

D. Tsoutsou, L. Lamagna, S. N. Volkos, A. Molle, S. Baldovino, S. Schamm, P. E. Coulon, and M. Fanciulli

Appl. Phys. Lett. 94, 053504 (2009); http://dx.doi.org/10.1063/1.3075609 (3 pages) | Cited 15 times

Online Publication Date: 3 February 2009

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Thin LaxZr1−xO2−δ (x = 0.25) high permittivity (k) films are grown on Si(100) by atomic layer deposition at 300 °C using (iPrCp)3La, (MeCp)2ZrMe(OMe) and O3 species. Their properties are studied by grazing incidence x-ray diffraction, high resolution transmission electron microscopy, electron energy loss spectroscopy, x-ray photoelectron spectroscopy, and electrical measurements on the as-grown films and after vacuum annealing at 600 °C. Annealed films feature resistance to hygroscopicity, a large k value of around 30 and an acceptable leakage current density. A low-k silica-rich interlayer is also evidenced at both pristine and annealed high-k/Si interfaces.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films
79.20.Uv Electron energy loss spectroscopy
79.60.Jv Interfaces; heterostructures; nanostructures
77.22.Ch Permittivity (dielectric function)

Gate voltage dependence on hot carrier degradation at an elevated temperature in a device with ultrathin silicon oxynitride

Minseok Jo, Seonghyun Kim, Chunhum Cho, Man Chang, and Hyunsang Hwang

Appl. Phys. Lett. 94, 053505 (2009); http://dx.doi.org/10.1063/1.3077611 (3 pages) | Cited 1 time

Online Publication Date: 3 February 2009

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The effects of hot carrier stress (HCS) at elevated temperature on a device with ultrathin silicon oxynitride have been investigated. It was shown that the degradation of the device was more significant at elevated temperature compared with at room temperature. This behavior attributed to more generation of interface states due to an increase in the high-energy tail electrons. By the theory of electron-electron scattering, the threshold voltage shift was the most severe at the condition of VG>VD. However, based on the results of extrapolating the device lifetime, the worst case stress condition under HCS was the VG = VD condition at elevated temperature due to a higher generation rate.
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85.75.Hh Spin polarized field effect transistors
85.30.Tv Field effect devices

Surface leakage reduction in narrow band gap type-II antimonide-based superlattice photodiodes

Edward Kwei-wei Huang, Darin Hoffman, Binh-Minh Nguyen, Pierre-Yves Delaunay, and Manijeh Razeghi

Appl. Phys. Lett. 94, 053506 (2009); http://dx.doi.org/10.1063/1.3078282 (3 pages) | Cited 25 times

Online Publication Date: 3 February 2009

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Inductively coupled plasma (ICP) dry etching rendered structural and electrical enhancements on type-II antimonide-based superlattices compared to those delineated by electron cyclotron resonance (ECR) with a regenerative chemical wet etch. The surface resistivity of 4×105 Ω cm is evidence of the surface quality achieved with ICP etching and polyimide passivation. By only modifying the etching technique in the fabrication steps, the ICP-etched devices with a 9.3 μm cutoff wavelength revealed a diffusion-limited dark current density of 4.1×10−6 A/cm2 and a maximum differential resistance at zero bias in excess of 5300 Ω cm2 at 77 K, which are an order of magnitude better in comparison to the ECR-etched devices.
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85.60.Dw Photodiodes; phototransistors; photoresistors
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
73.25.+i Surface conductivity and carrier phenomena
81.65.Rv Passivation
72.40.+w Photoconduction and photovoltaic effects

Optical modeling of chalcopyrite-based tandems considering realistic layer properties

M. Schmid, J. Krč, R. Klenk, M. Topič, and M. Ch. Lux-Steiner

Appl. Phys. Lett. 94, 053507 (2009); http://dx.doi.org/10.1063/1.3077613 (3 pages) | Cited 6 times

Online Publication Date: 4 February 2009

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Previous models of chalcopyrite-based tandem solar cells have not taken into account the limited optical transmission of the top cell observed. We use a quantitative model derived from measured optical properties of the different layers of the top cell to re-evaluate the benefits and limitations of the tandems. Guidelines are provided for minimizing optical losses in the structure. Optimization of the bottom absorber band gap and top absorber thickness is carried out. In combination with straightforward assumptions concerning the electronic cell properties, we calculate tandem maximum efficiencies in the range of 26%–28% depending on the degree of nonideal optical absorption.
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84.60.Jt Photoelectric conversion

Dependence of charge trapping and tunneling on the silicon-nitride (Si3N4) thickness for tunnel barrier engineered nonvolatile memory applications

Myung-Ho Jung, Kwan-Su Kim, Goon-Ho Park, and Won-Ju Cho

Appl. Phys. Lett. 94, 053508 (2009); http://dx.doi.org/10.1063/1.3078279 (3 pages) | Cited 10 times

Online Publication Date: 5 February 2009

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Charge trapping and tunneling characteristics of silicon-nitride (Si3N4) layer with various thicknesses were investigated for applications of tunnel barrier engineered nonvolatile memory (NVM). A critical thickness of Si3N4 layer for suppressing the charge trapping and enhancing the tunneling sensitivity of tunnel barrier were developed. Also, the charge trap centroid and charge trap density were extracted by constant current stress method. As a result, the optimization of Si3N4 thickness considerably improved the performances of NVM.
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84.30.Sk Pulse and digital circuits
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
77.55.-g Dielectric thin films
73.40.Gk Tunneling
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

A 32.6% efficient lattice-matched dual-junction solar cell working at 1000 suns

I. García, I. Rey-Stolle, B. Galiana, and C. Algora

Appl. Phys. Lett. 94, 053509 (2009); http://dx.doi.org/10.1063/1.3078817 (3 pages) | Cited 14 times

Online Publication Date: 5 February 2009

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Photovoltaic conversion efficiencies of 32.6% and 30% at concentrations of 1000 and 3500 suns, respectively, are achieved in monolithic GaInP/GaAs dual-junction solar cells grown lattice matched on a GaAs substrate by metal-organic vapor-phase epitaxy. The tunnel-junction design, based on an (Al)GaAs/GaAs heterojunction, is found to be a key factor for achieving this efficiency at such high concentrations. Moreover, the thorough design and joint optimization of the front grid and the top-cell emitter, using quasi-three-dimensional distributed models, also plays a major role. Efficiencies of over 40% at 1000 suns should be achieved by extending this approach to triple-junction devices.
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84.60.Jt Photoelectric conversion
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Role of TaON interface for CuxO resistive switching memory based on a combined model

P. Zhou (周鹏), M. Yin (尹明), H. J. Wan (万海军), H. B. Lu (吕杭炳), T. A. Tang (汤庭鳌), and Y. Y. Lin (林殷茵)

Appl. Phys. Lett. 94, 053510 (2009); http://dx.doi.org/10.1063/1.3078824 (3 pages) | Cited 13 times

Online Publication Date: 5 February 2009

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For the embedded application of the resistive switching memory using CuxO films, the controllable switching polarity and optimized low resistance state was investigated. Stable bipolar switching behavior was demonstrated for the TaN/CuxO/Cu device. TaON was observed at the anode interface by x-ray photoelectron spectroscopy and transmission electron microscopy, which is believed to play a key role in the resistance transition. The physics behind this phenomenon of reactive top-electrode is revealed. A filament/charges trapped combined model is proposed to clarify the electrical characteristics of the top-electrode/oxide reactions. This observation presents a unique opportunity to elucidate a universal mechanism for the resistive switching of transitional metal oxides.
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84.30.Sk Pulse and digital circuits
72.60.+g Mixed conductivity and conductivity transitions
79.60.Jv Interfaces; heterostructures; nanostructures
68.37.Lp Transmission electron microscopy (TEM)

Junctionless multigate field-effect transistor

Chi-Woo Lee, Aryan Afzalian, Nima Dehdashti Akhavan, Ran Yan, Isabelle Ferain, and Jean-Pierre Colinge

Appl. Phys. Lett. 94, 053511 (2009); http://dx.doi.org/10.1063/1.3079411 (2 pages) | Cited 49 times

Online Publication Date: 6 February 2009

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This paper describes a metal-oxide-semiconductor (MOS) transistor concept in which there are no junctions. The channel doping is equal in concentration and type to the source and drain extension doping. The proposed device is a thin and narrow multigate field-effect transistor, which can be fully depleted and turned off by the gate. Since this device has no junctions, it has simpler fabrication process, less variability, and better electrical properties than classical MOS devices with source and drain PN junctions.
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85.30.Tv Field effect devices
85.75.Hh Spin polarized field effect transistors
61.72.U- Doping and impurity implantation

Anisotropic optical response of InAs/InP quantum dot avalanche photodiodes

C. K. Chia, J. R. Dong, and B. K. Ng

Appl. Phys. Lett. 94, 053512 (2009); http://dx.doi.org/10.1063/1.3079674 (3 pages) | Cited 2 times

Online Publication Date: 6 February 2009

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Polarization resolved photocurrents in InAs/InP quantum dot (QD) avalanche photodiodes (APDs) comprising of three InAs QD layers have been determined under normal incidence. The responsivity of the InAs/InP APD from 1550 nm illumination was found to increase rapidly with increasing avalanche gain. Energy separation between the heavy-hole ground-state (hh1-e1) and heavy-hole excited-state (hh2-e2) absorptions was found to increase linearly with increasing applied electric field. The difference between the photocurrents corresponds to the hh1-e1 and hh2-e2 transitions, which increases exponentially after the onset of multiplication, suggesting the TE and TM polarization effects on the photoresponse of the InAs/InP APDs are amplified by the avalanche multiplication process.
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85.60.Dw Photodiodes; phototransistors; photoresistors

A comparative study of effects of SiNx deposition method on AlGaN/GaN heterostructure field-effect transistors

Masataka Higashiwaki, Zhen Chen, Rongming Chu, Yi Pei, Stacia Keller, Umesh K. Mishra, Nobumitsu Hirose, Toshiaki Matsui, and Takashi Mimura

Appl. Phys. Lett. 94, 053513 (2009); http://dx.doi.org/10.1063/1.3079798 (3 pages) | Cited 7 times

Online Publication Date: 6 February 2009

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The effects of thin SiNx deposition on AlGaN/GaN heterostructure field-effect transistors were systematically studied by comparing their electrical and device characteristics. Two aspects of the thin SiNx film deposition were investigated: (i) the increase in two-dimensional electron gas (2DEG) density at the heterointerface and (ii) its capability as a gate insulating layer. Three different SiNx deposition methods were studied: catalytic chemical vapor deposition (Cat-CVD), metalorganic chemical vapor deposition (MOCVD), and plasma enhanced chemical vapor deposition (PECVD). A large increase in 2DEG density was obtained after SiNx deposition for all methods. The devices with MOCVD SiNx gate insulator showed a larger gate leakage current than those with the Cat-CVD and PECVD SiNx, implying that a thinning of the AlGaN surface barrier occurred due to Si diffusion into the AlGaN barrier during the high-temperature MOCVD process.
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85.30.Tv Field effect devices
85.40.Sz Deposition technology
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