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13 Oct 2008

Volume 93, Issue 15, Articles (15xxxx)

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Appl. Phys. Lett. 93, 151101 (2008); http://dx.doi.org/10.1063/1.2996271 (3 pages)

Xuefeng Zeng and Hongrui Jiang
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Electron irradiation of AlGaN/GaN and AlN/GaN heterojunctions

A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, A. V. Markov, S. J. Pearton, A. M. Dabiran, A. M. Wowchak, B. Cui, A. V. Osinsky, P. P. Chow, N. G. Kolin, V. M. Boiko, and D. I. Merkurisov

Appl. Phys. Lett. 93, 152101 (2008); http://dx.doi.org/10.1063/1.3000613 (3 pages) | Cited 10 times

Online Publication Date: 13 October 2008

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The effects of 10 MeV electron irradiation on AlGaN/GaN and AlN/GaN heterojunctions grown by molecular beam epitaxy are reported. The irradiation increases the resistivity of the GaN buffer due to compensation by radiation defects with levels near Ec−1 eV and decreases the mobility of the two-dimensional electron gas (2DEG) near the AlGaN/GaN (or AlN/GaN) interface. The bulk carrier removal rate in the GaN buffer is the same for both types of structures and similar to carrier removal rates for undoped n-GaN films. In structures with a density of residual donors of ∼ 1015 cm−3, irradiation with electron doses of ∼ 5×1015 cm−2 renders the buffer semi-insulating. The 50% degradation of the 2DEG conductivity happens at several times higher doses (close to 3×1016 cm−2 versus 6.5×1015 cm−2) for AlN/GaN than for AlGaN/GaN structures, most likely because of the lower thickness of the AlN barrier.
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61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance

MgO thickness dependence of spin injection efficiency in spin-light emitting diodes

Y. Lu, V. G. Truong, P. Renucci, M. Tran, H. Jaffrès, C. Deranlot, J.-M. George, A. Lemaître, Y. Zheng, D. Demaille, P.-H. Binh, T. Amand, and X. Marie

Appl. Phys. Lett. 93, 152102 (2008); http://dx.doi.org/10.1063/1.2999631 (3 pages) | Cited 9 times

Online Publication Date: 13 October 2008

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We have studied the electron spin injection efficiency from a CoFeB/MgO spin injector into AlGaAs/GaAs semiconductor light emitting diodes. The circular polarization of the electroluminescence signal reaches a value as large as 32% at 100 K under a 0.8 T magnetic field. We show that the spin injection efficiency increases with the increase in the MgO barrier thickness from 1.4 to 4.3 nm. Moreover, a higher spin injection efficiency is obtained for MgO barriers grown at 300 °C compared to the ones grown at room temperature. This effect is attributed to the MgO texturing occurring at high temperatures.
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85.60.Jb Light-emitting devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

Electric field induced phase transition in charge-ordered LuFe2O4

Changhui Li, Xiangqun Zhang, Zhaohua Cheng, and Young Sun

Appl. Phys. Lett. 93, 152103 (2008); http://dx.doi.org/10.1063/1.3001591 (3 pages) | Cited 24 times

Online Publication Date: 14 October 2008

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The measurements of resistance under various applied voltages as well as the highly nonlinear current-voltage characteristics reveal that a small electric field is able to induce an insulating to metallic phase transition in LuFe2O4. The threshold field at which the phase transition occurs decreases exponentially with the increasing temperature. We interpret this transition as a consequence of the breakdown of the charge-ordered state triggered by applied electric field. This electrically driven phase transition results in a colossal electroresistance effect around room temperature which makes LuFe2O4 a very promising material for many applications.
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81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
68.35.Rh Phase transitions and critical phenomena

Transfer characteristics in graphene field-effect transistors with Co contacts

Ryo Nouchi, Masashi Shiraishi, and Yoshishige Suzuki

Appl. Phys. Lett. 93, 152104 (2008); http://dx.doi.org/10.1063/1.2998396 (3 pages) | Cited 21 times

Online Publication Date: 14 October 2008

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Graphene field-effect transistors with Co contacts as source and drain electrodes show anomalous distorted transfer characteristics. The anomaly appears only in short-channel devices (shorter than approximately 3 μm) and originates from a contact-induced effect. Band alteration of a graphene channel by the contacts is discussed as a possible mechanism for the anomalous characteristics observed.
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85.30.Tv Field effect devices

Impact of quantum confinement and quantum confined Stark effect on biexciton binding energy in GaN/AlGaN quantum wells

F. Stokker-Cheregi, A. Vinattieri, E. Feltin, D. Simeonov, J. Levrat, J.-F. Carlin, R. Butté, N. Grandjean, and M. Gurioli

Appl. Phys. Lett. 93, 152105 (2008); http://dx.doi.org/10.1063/1.2973897 (3 pages) | Cited 1 time

Online Publication Date: 15 October 2008

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We report on time-resolved photoluminescence measurements carried out along the thickness gradient of two types of GaN/AlGaN quantum wells with low Al content in the barriers (5% and 9%, respectively). A reduction of the biexciton binding energy with increasing well thickness is observed, as a result of the reduced quantum confinement and the increasing impact of the quantum confined Stark effect. In the sample with 5% Al content in the barriers, for thicknesses of the well region larger than ∼ 9 monolayers, the biexciton binding energy is found to be smaller than that measured for bulk GaN.
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73.21.Fg Quantum wells
78.20.Jq Electro-optical effects
78.47.jd Time resolved luminescence
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.35.-y Excitons and related phenomena

Excess-silver-induced bridge formation in a silver sulfide atomic switch

Zhongchang Wang, Tingkun Gu, Tomofumi Tada, and Satoshi Watanabe

Appl. Phys. Lett. 93, 152106 (2008); http://dx.doi.org/10.1063/1.2963197 (3 pages) | Cited 12 times

Online Publication Date: 15 October 2008

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Structural properties and electron transport of a Ag2S atomic switch composed of Ag–Ag2S–Ag heterostructure are investigated by nonequilibrium Green’s function calculations considering the effect of excess Ag in the Ag2S layer. In addition to confirming experimentally the formation of the Ag bridge inside Ag2S, the bridge is found to consist of units having a structure similar to that of the Ag (111) face in the bulk Ag. The analyses of Mulliken population, transmission spectra, and current-voltage characteristics reveal that the bridge has a conductive and metallic nature.
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85.35.-p Nanoelectronic devices
84.32.Dd Connectors, relays, and switches

Field-induced semiconductor-metal transition in individual NiO–Ni Schottky nanojunction

Xingchen Zhao, Jia-Lin Sun, and Jia-Lin Zhu

Appl. Phys. Lett. 93, 152107 (2008); http://dx.doi.org/10.1063/1.2998574 (3 pages) | Cited 4 times

Online Publication Date: 15 October 2008

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Ni nanowire arrays were obtained by electrochemical deposition in a template. After oxidation, one-dimensional NiO–Ni Schottky junctions with nanoscale-thickness NiO layer were achieved, and the structure was characterized in terms of different scales. By application of an electric field through atomic force microscopy, the semiconductor-metal transition was observed and an enhanced nonlinearity was found in the individual Schottky nanojunction at room temperature. This kind of Schottky nanojunction requires no doping and may provide a wide variety of applications in the future.
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73.30.+y Surface double layers, Schottky barriers, and work functions
87.80.Kc Electrochemical techniques
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Internal gettering of iron in multicrystalline silicon at low temperature

Rafael Krain, Sandra Herlufsen, and Jan Schmidt

Appl. Phys. Lett. 93, 152108 (2008); http://dx.doi.org/10.1063/1.2987521 (3 pages) | Cited 15 times

Online Publication Date: 17 October 2008

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The interstitial iron concentration in multicrystalline silicon wafers, determined from recombination lifetime measurements, is effectively reduced by annealing the wafers at very low temperature (300–500 °C). During annealing, the iron concentration decreases by more than one order of magnitude. The observed disappearance of interstitial iron is explained by internal gettering of the iron by crystallographic defects.
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81.05.Cy Elemental semiconductors
81.65.Tx Gettering
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.Cc Kinetics of defect formation and annealing
61.72.jj Interstitials
61.72.sd Impurity concentration

Deuterium diffusion and trapping in hydrothermally grown single crystalline ZnO

K. M. Johansen, J. S. Christensen, E. V. Monakhov, A. Yu. Kuznetsov, and B. G. Svensson

Appl. Phys. Lett. 93, 152109 (2008); http://dx.doi.org/10.1063/1.3001605 (3 pages) | Cited 13 times

Online Publication Date: 17 October 2008

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Secondary ion mass spectrometry is employed to investigate diffusion of 2H implanted in hydrothermally grown single crystal ZnO. Diffusion profiles have been studied after 30 min isochronal heat treatments from 100 to 400 °C and evaluated using three different models: the infinite source model, a solid solubility limited model, and a trap limited model. Only the latter one reproduces closely the measured values. From this model an activation energy Ea = 0.85 eV is extracted, and it is speculated that trapping may be a source of the discrepancies between the reported values of Ea in the literature.
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66.30.-h Diffusion in solids
81.10.Dn Growth from solutions
61.72.uj III-V and II-VI semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.40.Gh Other heat and thermomechanical treatments

Low temperature electric pulse induced resistance switching in Na0.5−δCoO2

G. Garbarino, M. Núñez-Regueiro, M. Armand, and P. Lejay

Appl. Phys. Lett. 93, 152110 (2008); http://dx.doi.org/10.1063/1.2931701 (3 pages) | Cited 5 times

Online Publication Date: 17 October 2008

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We have been able to control the resistance state of the NaxCoO2 system for the x = 0.5−δ sample at low temperatures by the application of current pulses. We can reversibly commute between two resistance states, controlling the amplitude and polarity of the applied pulses. We also studied the resistance temperature dependence of the different state and we interpret the switching effect in term of the displacement of Na+ ions induced by current.
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72.60.+g Mixed conductivity and conductivity transitions
72.80.Sk Insulators
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