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16 Jun 2003

Volume 82, Issue 24, pp. 4215-4390

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 4322 (2003); http://dx.doi.org/10.1063/1.1582366 (3 pages)

Hongwei Qu, Wei Yao, T. Garcia, Jiandi Zhang, A. V. Sorokin, S. Ducharme, P. A. Dowben, and V. M. Fridkin
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Impact of Si doping on radio frequency dispersion in unpassivated GaN/AlGaN/GaN high-electron-mobility transistors grown by plasma-assisted molecular-beam epitaxy

Oleg Mitrofanov, Michael Manfra, and Nils Weimann

Appl. Phys. Lett. 82, 4361 (2003); http://dx.doi.org/10.1063/1.1582373 (3 pages) | Cited 23 times

Online Publication Date: 10 June 2003

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We report on the effect of Si doping on the transient behavior of unpassivated high-power GaN/AlGaN/GaN high-electron-mobility transistors grown by plasma-assisted molecular-beam epitaxy on 6H–SiC. The incorporation of Si into the heterostructure barrier is found to reduce the level of radio frequency dispersion as compared to undoped structures. In some devices which incorporate Si doping of the barrier, the pulsed and steady-state current–voltage characteristics coincide, and gate lag is found to be insignificant. More typically, ∼90% of the dc value of drain current is restored at 1 μs after pulsing the gate from pinch off to VGS = 0 V. Significant gate lag is observed in devices that are not doped with Si. In the undoped structure, the drain current reaches only ∼70% of the dc value within 1 μs. The transient behavior in the two designs is attributed to the same defect state with activation energy of 0.22 eV. Dispersion reduction is correlated with an increase of gate leakage current in Si-doped devices. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
73.50.Mx High-frequency effects; plasma effects
73.61.Ey III-V semiconductors
61.72.uj III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Barrier heights of Schottky contacts on strained AlGaN/GaN heterostructures: Determination and effect of metal work functions

Zhaojun Lin, Wu Lu, Jaesun Lee, Dongmin Liu, Jeffrey S. Flynn, and George R. Brandes

Appl. Phys. Lett. 82, 4364 (2003); http://dx.doi.org/10.1063/1.1584077 (3 pages) | Cited 33 times

Online Publication Date: 10 June 2003

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Ir, Ni, and Re Schottky contacts on strained Al0.25Ga0.75N/GaN heterostructures are characterized using capacitance–voltage (C–V) and I–V techniques. Based on the measured C–V characteristics, two dimensional electron gas sheet carrier concentrations at the AlGaN/GaN interface and barrier heights of Ir, Ni, and Re Schottky contacts are calculated. The barrier heights of 1.12, 1.27, and 1.68 eV are obtained for Ir, Ni, and Re Schottky contacts, respectively. The results show that the barrier heights of Schottky contacts on strained AlGaN/GaN heterostructures are strongly dependent on the metal work functions. However, contrary to Schottky contacts on bulk AlGaN or GaN, the barrier height on strained AlGaN/GaN heterostructures is lower for a Schottky contact with a higher metal work function. This is attributed to the stronger wave function coupling between electrons in the Schottky metal and surface donor electrons. The I–V characteristics for Ir, Ni, and Re Schottky contacts confirm the results obtained by C–V characteristics. © 2003 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Ns Metal-nonmetal contacts

Temperature dependence on current–voltage characteristics of nickel/diamond Schottky diodes on high quality boron-doped homoepitaxial diamond film

Y. G. Chen, M. Ogura, and H. Okushi

Appl. Phys. Lett. 82, 4367 (2003); http://dx.doi.org/10.1063/1.1583868 (3 pages) | Cited 15 times

Online Publication Date: 10 June 2003

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Ni/diamond Schottky diodes were fabricated on boron-doped homoepitaxial diamond films. Temperature dependence on electrical characteristics of the Schottky diodes was investigated in a temperature range 148 to ∼448 K. The current–voltage characteristics of the diodes show excellent rectification behavior. Temperature dependence on the ideality factor and apparent barrier height was determined, including the effect of series resistance. The evaluated ideality factor was observed to decrease from 1.78 to 1.05, while the apparent barrier height increased from 0.95 to 1.55 eV in this temperature range. The temperature dependence of the forward characteristics can be well explained by thermionic-field-emission theory at low temperature and thermionic emission theory at high temperature, respectively. A possible mechanism of the correlation of the ideality factor and barrier height has been proposed. © 2003 American Institute of Physics.
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85.30.Kk Junction diodes

Quality assessment of CuInS2-based solar cells by Raman scattering

E. Rudigier, I. Luck, and R. Scheer

Appl. Phys. Lett. 82, 4370 (2003); http://dx.doi.org/10.1063/1.1582362 (3 pages) | Cited 18 times

Online Publication Date: 10 June 2003

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In this work spectroscopic features of the Raman A1 mode of CuInS2 thin films are investigated. A broadening of the A1 mode in combination with an asymmetry towards larger wave numbers is observed. The comparison with parameters of the solar cells formed out of these thin films reveal a direct correlation between the linewidth of the A1 mode and the solar cell data. A significant decrease of open circuit voltage and fill factor of the cells is found for linewidths larger than 3.8 cm−1. For linewidths smaller than 3.8 cm−1, a saturated behavior of the solar cell parameters is observed. This saturation indicates other origins of performance limitation to be present in CuInS2 based devices. © 2003 American Institute of Physics.
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84.60.Jt Photoelectric conversion
78.30.Hv Other nonmetallic inorganics
78.66.Li Other semiconductors

Flexible organic field-effect transistors fabricated by the electrode-peeling transfer with an assist of self-assembled monolayer

Katsuhiko Fujita, Takeshi Yasuda, and Tetsuo Tsutsui

Appl. Phys. Lett. 82, 4373 (2003); http://dx.doi.org/10.1063/1.1583867 (3 pages) | Cited 8 times

Online Publication Date: 10 June 2003

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We propose a way to fabricate a flexible organic field-effect transistor: an electrode-peeling transfer method. In this method, source–drain metal electrodes were formed finely on rigid temporary substrate, where a micropatterning process such as photolithography is applicable. The electrodes were treated with an alkane thiol to form a self-assembled monolayer followed by complete covering of the temporary substrate via chemical vapor deposition of an organic dielectric layer. After the gate electrode was deposited on the top, the multilayer of the source–drain electrodes/dielectric layer/gate electrode was peeled off from the temporary substrate by an adhesive Scotch tape substrate without deletion. The peeling-transfer was completed with an assist of a self-assembled monolayer as a connecting buffer layer between the electrodes and the dielectric layer. Any organic semiconductor materials can be deposited on freshly peeled-off surface of the flexible substrate. In the present case, pentacene was used as the semiconductor material. It showed a hole mobility exceeding 0.1 cm2/V s even after the substrate was rolled. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
85.65.+h Molecular electronic devices
85.40.Hp Lithography, masks and pattern transfer
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
72.20.Fr Low-field transport and mobility; piezoresistance
73.50.Dn Low-field transport and mobility; piezoresistance

Theory of avalanche multiplication and excess noise in quantum-well infrared photodetectors

Harald Schneider

Appl. Phys. Lett. 82, 4376 (2003); http://dx.doi.org/10.1063/1.1585134 (3 pages) | Cited 9 times

Online Publication Date: 10 June 2003

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A theoretical treatment of the noise current of quantum-well infrared photodetectors in the presence of avalanche multiplication is presented. Avalanche multiplication results in a characteristic excess noise which is expressed as a function of the avalanche multiplication factor and the capture probability. The multiplication factor can thus be determined from the photoconductive gain and the noise gain. © 2003 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
72.20.Ht High-field and nonlinear effects
72.40.+w Photoconduction and photovoltaic effects
72.70.+m Noise processes and phenomena
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