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1 Jul 2002

Volume 81, Issue 1, pp. 1-184

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Majority- and minority-carrier deep level traps in proton-irradiated n+/p-InGaP space solar cells

Nethaji Dharmarasu, Masafumi Yamaguchi, Jacques C. Bourgoin, Tatsuya Takamoto, Takeshi Ohshima, Hisayoshi Itoh, Mitsuru Imaizumi, and Sumio Matsuda

Appl. Phys. Lett. 81, 64 (2002); http://dx.doi.org/10.1063/1.1491005 (3 pages) | Cited 6 times

Online Publication Date: 25 June 2002

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We report the properties of observed defects in n+/p-InGaP solar cells created by irradiation of protons of different energies. Three majority (hole) and a minority-carrier traps, labeled respectively as HP1 (Ev+0.90±0.05 eV), HP2 (Ev+0.73±0.05 eV), H2 (Ev+0.55 eV), and EP1 (Ec−0.54 eV), were identified using deep level transient spectroscopy. All majority-carrier traps were found to act as recombination centers. While the H2 trap present in the proton-irradiated p-InGaP was found to anneal out by minority-carrier injection, the other traps were not. © 2002 American Institute of Physics.
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84.60.Jt Photoelectric conversion
71.55.Eq III-V semiconductors
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Terahertz intersubband emission in strong magnetic fields

Stéphane Blaser, Michel Rochat, Mattias Beck, Daniel Hofstetter, and Jérôme Faist

Appl. Phys. Lett. 81, 67 (2002); http://dx.doi.org/10.1063/1.1490629 (3 pages) | Cited 21 times

Online Publication Date: 25 June 2002

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Electroluminescence in quantum-cascade structures based on vertical transitions is studied in a strong perpendicular magnetic field in the limit in which the cyclotron energy is larger than the intersubband transition energy. Cyclotron emission and a luminescence intensity enhancement up to a factor of 6 is observed in GaAs/AlGaAs and InGaAs/InAlAs vertical transition-based quantum-cascade structures. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.60.Fi Electroluminescence
78.20.Ls Magneto-optical effects

Low-resistivity, p-type SiC layers produced by Al implantation and ion-beam-induced crystallization

V. Heera, K. N. Madhusoodanan, A. Mücklich, D. Panknin, and W. Skorupa

Appl. Phys. Lett. 81, 70 (2002); http://dx.doi.org/10.1063/1.1490145 (3 pages) | Cited 7 times

Online Publication Date: 25 June 2002

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Low-resistivity (<0.1 Ω cm), p-type SiC layers of about 500 nm width and targeted acceptor concentrations of 1.5×1020 cm−3 and 5.0×1020 cm−3 were produced by the combination of high-dose (1.0 and 3.3×1016 cm−2), multienergy (50–450 keV) Al+ ion implantation of 6H-SiC at −130 °C, ion-beam-induced crystallization with 500 keV, 5×1015 Si+ cm−2 at 500 °C and subsequent furnace annealing at 1500 °C for 10 min. The implanted SiC layers have a nanocrystalline structure consisting of randomly oriented grains of mainly 3C-SiC. The electrical properties of the doped, nanocrystalline layers were investigated by sheet resistance and Hall measurements in dependence on temperature and compared with results from single-crystalline reference samples. In comparison with the standard doping process, the hole concentration at 50 °C is enhanced by more than one order of magnitude from 9.0×1017 cm−3 to 1.6×1019 cm−3 in the case of 1.5×1020 Al cm−3 and from 6.1×1018 cm−3 to 8.0×1019 cm−3 in the case of 5.0×1020 Al cm−3, respectively. It can be speculated that the loss of active Al acceptors by precipitation is reduced in the nanocrystalline layers and, therefore, the critical concentration for the formation of an impurity band can be achieved. © 2002 American Institute of Physics.
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61.72.up Other materials
61.80.Jh Ion radiation effects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Le Other inorganic semiconductors
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.46.-w Structure of nanoscale materials
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
64.75.-g Phase equilibria
71.55.Ht Other nonmetals

n-type doping of oxides by hydrogen

Çetin Kılıç and Alex Zunger

Appl. Phys. Lett. 81, 73 (2002); http://dx.doi.org/10.1063/1.1482783 (3 pages) | Cited 90 times

Online Publication Date: 25 June 2002

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First-principles total-energy calculations suggest that interstitial hydrogen impurity forms a shallow donor in SnO2, CdO, and ZnO, but a deep donor in MgO. We generalize this result to other oxides by recognizing that there exist a “hydrogen pinning level” at about 3.0±0.4 eV below vacuum. Materials such as Ag2O, HgO, CuO, PbO, PtO, IrO2, RuO2, PbO2, TiO2, WO3, Bi2O3, Cr2O3, Fe2O3, Sb2O3, Nb2O5, Ta2O5, FeTiO3, and PbTiO3, whose conduction band minimum (CBM) lie below this level (i.e., electron affinity>3.0±0.4 eV) will become conductive once hydrogen is incorporated into the lattice, without reducing the host. Conversely, materials such as BaO, NiO, SrO, HfO2, and Al2O3, whose CBM lie above this level (i.e., electron affinity<3.0±0.4 eV) will remain nonconductive since hydrogen forms a deep impurity. © 2002 American Institute of Physics.
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71.55.Ht Other nonmetals
61.72.J- Point defects and defect clusters
71.15.Nc Total energy and cohesive energy calculations

Large enhancement in room-temperature magnetoresistance and dramatic decrease in resistivity in La0.7Ca0.3MnO3–Ag composites

Yun-Hui Huang, Chun-Hua Yan, Feng Luo, Wei Song, Zhe-Ming Wang, and Chun-Sheng Liao

Appl. Phys. Lett. 81, 76 (2002); http://dx.doi.org/10.1063/1.1491029 (3 pages) | Cited 40 times

Online Publication Date: 25 June 2002

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A ferromagnet-metal-type composite, La0.7Ca0.3MnO3 (LCMO)–Ag, was fabricated by a two-step chemical route which can avoid the doping of Ag into the lattice of LCMO. The grain size of Ag can be reduced by increasing calcination temperature, which favors the penetration of Ag into LCMO matrices. A large enhancement in magnetoresistance (MR) near room temperature and a dramatic decrease in resistivity are observed for the samples calcined at above the melting temperature of Ag. We suggest that the shift of metal–insulator transition up to Curie temperature in melted-Ag-added LCMO and magnetic inhomogeneity are responsible for the enhanced MR. © 2002 American Institute of Physics.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.60.+g Mixed conductivity and conductivity transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
71.30.+h Metal-insulator transitions and other electronic transitions

Direct imaging of reverse-bias leakage through pure screw dislocations in GaN films grown by molecular beam epitaxy on GaN templates

J. W. P. Hsu, M. J. Manfra, R. J. Molnar, B. Heying, and J. S. Speck

Appl. Phys. Lett. 81, 79 (2002); http://dx.doi.org/10.1063/1.1490147 (3 pages) | Cited 11 times

Online Publication Date: 25 June 2002

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Excess reverse-bias leakage in GaN films grown by molecular beam epitaxy on GaN templates is correlated with the presence of pure screw dislocations. A scanning current–voltage microscope was used to map the spatial locations of leakage current on high quality GaN films under reverse bias. Two samples with similar total dislocation density ( ∼ 109 cm−2) but with pure screw dislocation density differing by an order of magnitude were compared. We found that the density of reverse-bias leakage spots correlates well with pure screw dislocation density, not with mixed dislocation density. Thus, pure screw dislocations have a far more detrimental impact on gate leakage than edge or mixed dislocations. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Hole and electron transport in strained Si: Orthorhombic versus biaxial tensile strain

F. M. Bufler and W. Fichtner

Appl. Phys. Lett. 81, 82 (2002); http://dx.doi.org/10.1063/1.1491283 (3 pages) | Cited 5 times

Online Publication Date: 25 June 2002

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Linear, nonlinear, and ballistic transport of holes and electrons in orthorhombically strained Si is theoretically analyzed at 300 K and compared with the results in biaxially tensily strained Si. At a Ge content of 30% in the strain-defining SiGe layer a drift mobility of about 1230 cm2/(V s) is found for holes under orthorhombic strain versus 1750 cm2/(V s) for tensile strain, while the stationary velocity in the nonlinear regime as well as the velocity overshoot peak are approximately the same. In the case of electrons, there is almost no difference between orthorhombic and tensile strain. © 2002 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Cw Elemental semiconductors
85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Femtosecond dynamics of exciton bleaching in bulk GaN at room temperature

Yin-Chieh Huang, Gia-Wei Chern, Kung-Hsuan Lin, Jian-Chin Liang, Chi-Kuang Sun, Chia-Chen Hsu, Stacia Keller, and Steven P. DenBaars

Appl. Phys. Lett. 81, 85 (2002); http://dx.doi.org/10.1063/1.1491296 (3 pages) | Cited 4 times

Online Publication Date: 25 June 2002

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Femtosecond transient transmission pump–probe technique was used to investigate exciton dynamics in a nominally undoped GaN thin film at room temperature. An exciton ionization time of 100–250 femtoseconds was observed by the time-resolved pump–probe measurement. A comparison experiment with pre-excited free carriers also confirmed the observation of the exciton ionization process in bulk GaN. © 2002 American Institute of Physics.
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71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.66.Fd III-V semiconductors
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
78.47.-p Spectroscopy of solid state dynamics

Do quasicrystals follow Wiedemann–Franz’s law?

Enrique Maciá

Appl. Phys. Lett. 81, 88 (2002); http://dx.doi.org/10.1063/1.1488696 (3 pages) | Cited 16 times

Online Publication Date: 25 June 2002

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In this work we present a theoretical study on the thermal and electrical conductivities of quasicrystals. By considering a realistic model for the spectral conductivity we derive closed analytical expressions for the transport coefficients which allow us to study the temperature dependence of the Lorenz ratio L(T) = κe(T)/Tσ(T) at different temperature regimes. We conclude that quasicrystals closely follow Wiedemann–Franz’s law over a wide temperature range. © 2002 American Institute of Physics.
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72.15.Cz Electrical and thermal conduction in amorphous and liquid metals and alloys
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
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