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28 Jan 2002

Volume 80, Issue 4, pp. 535-701

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Thermal stability study of Ni/Ta n-GaN Schottky contacts

G. L. Chen, F. C. Chang, K. C. Shen, J. Ou, W. H. Chen, M. C. Lee, W. K. Chen, M. J. Jou, and C. N. Huang

Appl. Phys. Lett. 80, 595 (2002); http://dx.doi.org/10.1063/1.1425455 (3 pages) | Cited 11 times

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The Schottky behavior of Ni/Ta and Ni contacts on n-GaN was investigated under various annealing conditions by current–voltage measurements. It is found that with the addition of Ta between the Ni layer and the GaN substrate the thermal stability properties of devices can be significantly improved. Experimental results indicate that a high quality Ni/Ta n-GaN Schottky diode with an ideality factor and barrier height of 1.16 and 1.24 eV, respectively, can be obtained under 1 h annealing, at 700 °C. © 2002 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.Kk Junction diodes
68.60.Dv Thermal stability; thermal effects
73.40.Ns Metal-nonmetal contacts
61.72.Cc Kinetics of defect formation and annealing
85.30.Hi Surface barrier, boundary, and point contact devices

High figure of merit in Eu-filled CoSb3-based skutterudites

G. A. Lamberton, S. Bhattacharya, R. T. Littleton, M. A. Kaeser, R. H. Tedstrom, T. M. Tritt, J. Yang, and G. S. Nolas

Appl. Phys. Lett. 80, 598 (2002); http://dx.doi.org/10.1063/1.1433911 (3 pages) | Cited 95 times

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We report measurements of electrical resistivity, thermopower, thermal conductivity, and Hall coefficient of polycrystalline Eu-doped CoSb3-based skutterudites with compositions Eu0.20Co4Sb12, Eu0.43Co4Sb11.59Ge0.31, and Eu0.42Co4Sb11.37Ge0.50. The relatively high mobility of these compounds, as compared to that of La- and Ce-filled skutterudites, may play a role in the large thermoelectric figure of merit (ZT>1 at 700 K) of Eu0.42Co4Sb11.37Ge0.50. We discuss the significant potential of these compounds for thermoelectric applications. © 2002 American Institute of Physics.
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72.80.Jc Other crystalline inorganic semiconductors
72.20.Pa Thermoelectric and thermomagnetic effects
72.20.My Galvanomagnetic and other magnetotransport effects
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Relaxed SiGe-on-insulator substrates without thick SiGe buffer layers

Tomohisa Mizuno, Naoharu Sugiyama, Tsutomu Tezuka, and Shin-ichi Takagi

Appl. Phys. Lett. 80, 601 (2002); http://dx.doi.org/10.1063/1.1435799 (3 pages) | Cited 17 times

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We have developed a technology for relaxing top SiGe layers with low dislocation density on Si substrates, without using thick SiGe buffer structures. By introducing a thin strained SiGe layer and the internal-oxidation (ITOX) process following the separation-by-implanted-oxygen (SIMOX) process, we have experimentally demonstrated relaxed SiGe-on-insulator (SGOI) substrates with the Ge content of 20%, and it has been realized that their dislocation density is a factor of 20 lower than that of SGOI with SiGe buffer layer. © 2002 American Institute of Physics.
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68.35.Ct Interface structure and roughness
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Lk Linear defects: dislocations, disclinations
61.72.uf Ge and Si
68.55.Nq Composition and phase identification
81.65.Mq Oxidation

Influence of 60Co γ-rays on dc performance of AlGaN/GaN high electron mobility transistors

B. Luo, J. W. Johnson, F. Ren, K. K. Allums, C. R. Abernathy, S. J. Pearton, A. M. Dabiran, A. M. Wowchack, C. J. Polley, P. P. Chow, D. Schoenfeld, and A. G. Baca

Appl. Phys. Lett. 80, 604 (2002); http://dx.doi.org/10.1063/1.1445809 (3 pages) | Cited 20 times

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AlGaN/GaN high electron mobility transistors (HEMTs) with different gate length and widths were irradiated with 60Co γ-rays to doses up to 600 Mrad. Little measurable change in dc performance of the devices was observed for doses lower than 300 Mrad. At the maximum dose employed, the forward gate current was significantly decreased, with an accompanying increase in reverse breakdown voltage. This is consistent with a decrease in effective carrier density in the channel as a result of the introduction of deep electron trapping states. The threshold voltage shifted to more negative voltages as a result of the irradiation, while the magnitude of the drain–source current was relatively unaffected. This is consistent with a strong increase of trap density in the material. The magnitude of the decrease in transconductance of the AlGaN/GaN HEMTs is roughly comparable to the decrease in dc current gain observed in InGaP/GaAs heterojunction bipolar transistors irradiated under similar conditions. © 2002 American Institute of Physics.
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85.30.Tv Field effect devices
61.80.Ed γ-ray effects
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.55.Eq III-V semiconductors
61.82.Fk Semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Transient model for terminal current noise

M. Nedjalkov, T. Grasser, H. Kosina, and S. Selberherr

Appl. Phys. Lett. 80, 607 (2002); http://dx.doi.org/10.1063/1.1447002 (3 pages)

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The condition of a stationary transport process is a common origin for the approaches for terminal current noise. Based on a recently-proposed stationary model and the integral form of the Boltzmann equation, we derive a transient stochastic process whose autocovariance function characterizes the terminal current noise. The properties and the domain of application of this transient model and its stationary counterpart are investigated. Numerical experiments are presented which support the conclusions drawn for the two models. © 2002 American Institute of Physics.
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72.70.+m Noise processes and phenomena
85.30.De Semiconductor-device characterization, design, and modeling
02.50.Ey Stochastic processes
05.60.-k Transport processes
02.30.Rz Integral equations
02.60.Nm Integral and integrodifferential equations
05.40.Ca Noise

Amorphous silicon thin-film transistors and arrays fabricated by jet printing

W. S. Wong, S. Ready, R. Matusiak, S. D. White, J.-P. Lu, J. Ho, and R. A. Street

Appl. Phys. Lett. 80, 610 (2002); http://dx.doi.org/10.1063/1.1436273 (3 pages) | Cited 25 times

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Phase-change wax-based printed masks, in place of conventional photolithography, were used to fabricate hydrogenated amorphous silicon thin-film transistors (TFTs). Wax-mask features with a minimum feature size of ∼20 μm were achieved using an acoustic-ink-printing process. Both discrete and matrix addressing structured bottom-gate TFTs with source–drain contacts overlapping the channel were created using a four-mask process. The TFTs had current–voltage characteristics comparable to photolithographically patterned devices, with mobility of 0.6–0.9 cm2/V s, threshold voltage of 2–3 V, and on/off ratios exceeding 107 for devices with channel lengths below 50 μm. © 2002 American Institute of Physics.
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85.30.Tv Field effect devices
85.40.Hp Lithography, masks and pattern transfer
73.61.Jc Amorphous semiconductors; glasses

Accurate impact ionization model which accounts for hot and cold carrier populations

T. Grasser, H. Kosina, C. Heitzinger, and S. Selberherr

Appl. Phys. Lett. 80, 613 (2002); http://dx.doi.org/10.1063/1.1445273 (3 pages) | Cited 3 times

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Conventional macroscopic impact ionization models which use the average carrier energy as a main parameter can not accurately describe the phenomenon in modern miniaturized devices. Here, we present a model which is based on an analytic expression for the distribution function. In particular, the distribution function model accounts explicitly for a hot and a cold carrier population in the drain region of metal–oxide–semiconductor transistors. The parameters are determined by three-even moments obtained from a solution of a six-moments transport model. Together with a nonparabolic description of the density of states, accurate closed form macroscopic impact ionization models can be derived based on familiar microscopic descriptions. © 2002 American Institute of Physics.
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72.20.Ht High-field and nonlinear effects
73.50.Fq High-field and nonlinear effects
72.30.+q High-frequency effects; plasma effects
73.50.Mx High-frequency effects; plasma effects
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