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13 Jan 2003

Volume 82, Issue 2, pp. 155-309

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 266 (2003); http://dx.doi.org/10.1063/1.1535271 (3 pages)

Jan Genzer, Daniel A. Fischer, and Kirill Efimenko
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Bright single-active layer small-molecular organic light-emitting diodes with a polytetrafluoroethylene barrier

Yudi Gao, Liduo Wang, Deqiang Zhang, Lian Duan, Guifang Dong, and Yong Qiu

Appl. Phys. Lett. 82, 155 (2003); http://dx.doi.org/10.1063/1.1536031 (3 pages) | Cited 32 times

Online Publication Date: 6 January 2003

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Single-layer organic light-emitting diodes (OLEDs) with a small molecule, tris(8-hydroxyquinoline) aluminum (Alq3) as the only active material, have been prepared. In order to achieve an efficient hole injection, a thin layer of polytetrafluoroethylene (Teflon) was inserted between the anode and the Alq3 layer. The effect of the Teflon layer thickness upon the device performance has also been investigated. A brightness of 16 000 cd/m2 with 6 nm thick Teflon layer was achieved, whereas the conventional double-layer OLEDs with N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′ biphenyl 4,4′-diamine and Alq3 showed only 9500 cd/m2 in our experiments. The single-layer structure technology is of great importance to the OLED’s commercialization due to its possible lower cost and higher production efficiency. And it is reasonable to infer that, based on this work, higher device performance could be realized by screening both the active material and the barrier layer material. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.61.Ph Polymers; organic compounds
78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence

Lasing characteristics of InGaAs/InGaAsP multiple-quantum-well optical thyristor operating at 1.561 μm

Doo Gun Kim, Hee Hyun Lee, Woon Kyung Choi, Young Wan Choi, Seok Lee, Deok Ha Woo, Young Tae Byun, Jae Hun Kim, Sun Ho Kim, and Yoshiaki Nakano

Appl. Phys. Lett. 82, 158 (2003); http://dx.doi.org/10.1063/1.1536711 (3 pages) | Cited 1 time

Online Publication Date: 6 January 2003

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We present a demonstration of a waveguide-type depleted optical thyristor laser diode with InGaAs/InGaAsP multiple-quantum-well structure. The measured switching voltage and current are 4.63 V and 10 μA, respectively. The holding voltage and current are, respectively, 0.59 V and 20 μA. The lasing threshold currents at 25 °C and 10 °C are 111 mA and 72.5 mA, respectively. The lasing wavelength is centered at 1.561 μm at a bias current equal to 1.41 times threshold. © 2003 American Institute of Physics.
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42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Imaging properties of a metamaterial superlens

Nicholas Fang and Xiang Zhang

Appl. Phys. Lett. 82, 161 (2003); http://dx.doi.org/10.1063/1.1536712 (3 pages) | Cited 119 times

Online Publication Date: 6 January 2003

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The subwavelength imaging quality of a metamaterial superlens is studied numerically in the wave vector domain. Examples of image compression and magnification are given and resolution limits are discussed. A minimal resolution of λ/6 is obtained using a 36 nm silver film at 364 nm wavelength. Simulation also reveals that the power flux is no longer a good measure to determine the focal plane of superlens due to the elevated field strength at exit side of the metamaterial slab. © 2003 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.-k Nonlinear optics

Generation of ultrawide-band chirped sources in the infrared through parametric interactions in periodically poled crystals

G. Marcus, A. Zigler, A. Englander, M. Katz, and Y. Ehrlich

Appl. Phys. Lett. 82, 164 (2003); http://dx.doi.org/10.1063/1.1537871 (3 pages) | Cited 1 time

Online Publication Date: 6 January 2003

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A method to generate chirped ultrawide-band sources with a chirp bandwidth of about 50% in the infrared is described and experimentally verified. It is based on optical parametric generation in periodically poled crystals with a chirped Ti:sapphire as a pump source. We have demonstrated a 27% wide bandwidth in the signal branch and 45% bandwidth in the idler branch when a periodically poled KTP crystal was pumped by a chirped Ti:sapphire laser with 12 nm full width at half maximum bandwidth. © 2003 American Institute of Physics.
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42.65.Lm Parametric down conversion and production of entangled photons
42.72.Ai Infrared sources
42.60.Fc Modulation, tuning, and mode locking
42.65.Yj Optical parametric oscillators and amplifiers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Time-resolved electroluminescence of AlGaN-based light-emitting diodes with emission at 285 nm

M. Shatalov, A. Chitnis, V. Mandavilli, R. Pachipulusu, J. P. Zhang, V. Adivarahan, S. Wu, G. Simin, M. Asif Khan, G. Tamulaitis, A. Sereika, I. Yilmaz, M. S. Shur, and R. Gaska

Appl. Phys. Lett. 82, 167 (2003); http://dx.doi.org/10.1063/1.1536729 (3 pages) | Cited 19 times

Online Publication Date: 6 January 2003

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We present a study on the time evolution of the electroluminescence (EL) spectra of AlGaN-based deep ultraviolet light-emitting diodes (LEDs) under pulsed current pumping. The EL spectra peaks at 285 nm and 330 nm are found to result from recombination involving band-to-band and free carriers to deep acceptor level transitions. The 330 nm long-wavelength transitions to deep acceptor levels in the p-AlGaN layer as well as the nonradiative processes significantly influence the LED internal quantum efficiency. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence

Terahertz pulse shaping via optical rectification in poled lithium niobate

Y.-S. Lee, N. Amer, and W. C. Hurlbut

Appl. Phys. Lett. 82, 170 (2003); http://dx.doi.org/10.1063/1.1535268 (3 pages) | Cited 20 times

Online Publication Date: 6 January 2003

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We demonstrate a technique for terahertz pulse shaping via optical rectification in the pre-engineered domain structure of poled lithium niobate crystals. The terahertz wave forms coincide with the crystal domain structures. The one-dimensional nonlinear wave equation simulates the experimental results with a good qualitative agreement. © 2003 American Institute of Physics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.An Optical susceptibility, hyperpolarizability
77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization

High efficiency organic light-emitting devices with Al/NaF cathode

J. Lee, Y. Park, D. Y. Kim, H. Y. Chu, H. Lee, and L.-M. Do

Appl. Phys. Lett. 82, 173 (2003); http://dx.doi.org/10.1063/1.1537048 (3 pages) | Cited 47 times

Online Publication Date: 6 January 2003

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An organic light-emitting device (OLED) with an Al/NaF (1.5 nm) cathode exhibited a highly enhanced performance comparable to the one with the best Al/LiF cathode. This suggests that NaF can be an alternative to commonly used LiF interlayer for improved OLED performance. Photoelectron spectroscopy studies revealed that the intensity of the gap states and the amount of the valence band shift at Al/NaF/Alq3 interface surpassed those of Al/LiF/Alq3 interface, suggesting that the observed performance improvement is directly related with these features. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
79.60.Jv Interfaces; heterostructures; nanostructures
73.20.At Surface states, band structure, electron density of states

Tuning efficiency and linewidth of electrostatically actuated multiple air-gap filters

F. Römer, C. Prott, S. Irmer, J. Daleiden, A. Tarraf, H. Hillmer, and M. Strassner

Appl. Phys. Lett. 82, 176 (2003); http://dx.doi.org/10.1063/1.1538353 (3 pages) | Cited 6 times

Online Publication Date: 6 January 2003

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We investigated the tuning efficiency of electrostatically actuated multiple air-gap filters fabricated in InP for dense wavelength division multiplex applications by comparing measured tuning curves with the results of optical and mechanical simulations. These filters exhibit a record tuning range of 127 nm at 7.3 V tuning voltage. The filters were measured in reflection using standard single mode fiber. The subsequent analysis is based on a one-dimensional electromechanical and optical model providing a reasonable estimation for the pull-in voltage. Optical simulations show that the filter linewidth does not affect the tuning efficiency. © 2003 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
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Emission of an intense electron beam from a ceramic honeycomb

M. Friedman, M. Myers, F. Hegeler, S. B. Swanekamp, J. D. Sethian, and L. Ludeking

Appl. Phys. Lett. 82, 179 (2003); http://dx.doi.org/10.1063/1.1537510 (3 pages) | Cited 11 times

Online Publication Date: 6 January 2003

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Inserting a slab of honeycomb ceramic in front of the emitting surface of a large-area cathode improves the electron beam emission uniformity, decreases the beam current rise and fall times, and maintains a more constant diode impedance. Moreover, changing the cathode material from velvet to carbon fiber achieved a more robust cathode that starts to emit at a higher electric field without a degradation in beam uniformity. In addition, an 80% reduction in the postshot diode pressure was also observed when gamma alumina was deposited on the ceramic. A possible explanation is that reabsorption and recycling of adsorbed gases takes place. © 2003 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
84.47.+w Vacuum tubes

Shaped electrode and lens for a uniform radio-frequency capacitive plasma

L. Sansonnens and J. Schmitt

Appl. Phys. Lett. 82, 182 (2003); http://dx.doi.org/10.1063/1.1534918 (3 pages) | Cited 35 times

Online Publication Date: 6 January 2003

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Plasma inhomogeneity caused by standing-wave effects in rf parallel plate reactors can be removed if one of the electrodes is replaced by a shaped electrode. The proposed shape is calculated using Maxwell’s equations in vacuum. In this solution, the electric field has a radially uniform vertical component, and a radial component which remains negligible for a plasma gap small compared to the quarter wavelength. Perturbations to this vacuum solution in presence of a plasma should remain small if the damping length due to dissipation in the plasma is large compared to the reactor radius and if the rf skin depth remains large compared to the plasma thickness. © 2003 American Institute of Physics.
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52.77.-j Plasma applications
52.80.Pi High-frequency and RF discharges
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Size-dependent Raman study of InP quantum dots

M. J. Seong, Olga I. Mićić, A. J. Nozik, A. Mascarenhas, and Hyeonsik M. Cheong

Appl. Phys. Lett. 82, 185 (2003); http://dx.doi.org/10.1063/1.1535272 (3 pages) | Cited 23 times

Online Publication Date: 6 January 2003

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Raman spectrum of a quantum dot (QD) is characterized by transverse (TO) and longitudinal (LO) optical modes as well as surface optical modes, occurring between the TO and LO modes. We have studied in detail the size-dependence of the Raman spectrum of InP QD of diameter larger than 35 Å. The LO phonon frequency decreases while the TO phonon frequency increases with decreasing QD size. The linewidth of the LO phonon broadens and the broadening becomes increasingly asymmetrical towards the low frequency side as the QD size decreases. By analyzing the Raman intensity ratio of the LO phonon to its overtone, we find that the electron-phonon coupling decreases with decreasing QD size. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.30.Fs III-V and II-VI semiconductors
68.35.Ja Surface and interface dynamics and vibrations
78.68.+m Optical properties of surfaces
63.20.K- Phonon interactions

Rate-dependent indentation hardness of a power-law creep solder alloy

Xin Ma and Fusahito Yoshida

Appl. Phys. Lett. 82, 188 (2003); http://dx.doi.org/10.1063/1.1537513 (3 pages) | Cited 8 times

Online Publication Date: 6 January 2003

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Berkovich depth-sensing indentation tests with different loading rates have been performed on a creep material, Sn–3.5Ag–0.75Cu solder alloy. The resulting indentation load-depth curves are rate dependent and have varying creep penetration depths during the same hold time. Creep indentation hardness H, defined from the concept of “work of indentation,” varies with the volume strain occurring during the creep hold time, which is a measure of creep strain rate mathcr. Thus, rate sensitivity m of the indented material can be determined from the ln H vs ln mathcr curve. The derived value of m is consistent with the results from conventional uniaxial tensile and compression experiments of bulk solder alloy. © 2003 American Institute of Physics.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Lm Deformation, plasticity, and creep
62.20.Qp Friction, tribology, and hardness
62.20.Hg Creep
62.20.M- Structural failure of materials

Surface acoustic wave applications of lithium niobate thin films

T.-C. Lee, J.-T. Lee, M. A. Robert, S. Wang, and T. A. Rabson

Appl. Phys. Lett. 82, 191 (2003); http://dx.doi.org/10.1063/1.1534413 (3 pages) | Cited 6 times

Online Publication Date: 6 January 2003

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A technique combining metalorganic decomposition and rf sputtering is used to grow lithium niobate (LiNbO3) thin films on diamond/silicon substrates, and surface acoustic wave (SAW) filters are fabricated by depositing interdigital transducers onto the multilayer LiNbO3/diamond/siliconstructures. Microwave characterization is achieved by using a network analyzer. Evidence is found for SAW propagation in these structures. These experimental findings agree with theoretical predictions. © 2003 American Institute of Physics.
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77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
43.35.Pt Surface waves in solids and liquids
77.55.-g Dielectric thin films
68.35.Iv Acoustical properties
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.15.Cd Deposition by sputtering
84.40.Dc Microwave circuits
84.30.Vn Filters

Synthesis and electronic structure of epitaxially stabilized Sr2−xLaxVO4 (0 ⩽ x ⩽ 1) thin films

J. Matsuno, Y. Okimoto, M. Kawasaki, and Y. Tokura

Appl. Phys. Lett. 82, 194 (2003); http://dx.doi.org/10.1063/1.1536030 (3 pages) | Cited 9 times

Online Publication Date: 6 January 2003

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We have synthesized a-axis-oriented epitaxial thin films of layered vanadate Sr2−xLaxVO4 on LaSrAlO4 (100) substrates using a pulsed-laser deposition technique. Epitaxial interface energy stabilizes compounds from V4+ (x = 0) to V3+ (x = 1), for which none of bulk single crystal has been synthesized. The transport property including its anisotropy has been studied to reveal metallic conduction for x = 0.15 and 0.2. The two-dimensional nature of the crystals gives insulating behavior along the c axis for all the compositions. Optical measurements indicate that the doped electrons are responsible for the insulator-to-metal transition as well as for the systematic variation of electronic structure from V4+ to V3+-based Mott insulators. © 2003 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
71.30.+h Metal-insulator transitions and other electronic transitions
73.20.At Surface states, band structure, electron density of states
68.55.-a Thin film structure and morphology

Nanosized iron clusters investigated with in situ transmission electron microscopy

T. Vystavel, G. Palasantzas, S. A. Koch, and J. Th. M. De Hosson

Appl. Phys. Lett. 82, 197 (2003); http://dx.doi.org/10.1063/1.1536716 (3 pages) | Cited 26 times

Online Publication Date: 6 January 2003

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Transmission electron microscopy is employed for investigating the structural stability of nanosized iron clusters as deposited and after in situ annealing treatments under high vacuum conditions. The thin iron oxide shell that is formed around the iron clusters (upon air exposure) is of the order of 2 nm surrounding a 5 nm core of body-centered-cubic (bcc) iron. The oxide shell breaks down upon annealing at relatively low temperatures ( ∼ 500 °C) leading to pure iron particles having a bcc crystal structure. Annealing of clusters, which are in contact, leads to their fusion and formation of larger clusters preserving their crystallographic structure and being free of any oxide shell. On the other hand, isolated clusters appear rather immobile (upon annealing). The truncated rhombic dodecahedron was found as the most probable shape of the clusters which differs from former theoretical predictions based on calculations of stable structural forms. © 2003 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
75.50.Tt Fine-particle systems; nanocrystalline materials
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.50.Bb Fe and its alloys

Transmission electron microscopy measurements of the injection distances in nanocrystal-based memories

G. Ben Assayag, C. Bonafos, M. Carrada, A. Claverie, P. Normand, and D. Tsoukalas

Appl. Phys. Lett. 82, 200 (2003); http://dx.doi.org/10.1063/1.1536026 (3 pages) | Cited 29 times

Online Publication Date: 6 January 2003

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The characteristics of nonvolatile memories making use of Si nanocrystals as charge storage elements buried in the gate oxide of regular metal–oxide–semiconductor transistors strongly depend on the distances between the nanocrystals and two electrodes, the channel and the gate. In this letter, we compare two transmission electron microscopy methods that can be used to extract such distances. We demonstrate by using image simulations that conventional electron microscopy under out-of-Bragg and strongly underfocused conditions is the fastest and most efficient technique to be used for routine measurements at a subnanometer resolution. Finally, we show that the injection oxide thickness of nanocrystal devices obtained by low-energy Si implantation into thin SiO2 layers and subsequent annealing can be precisely tuned from 8 to 5 nm by adjusting the implantation energy from 0.65 to 2 keV. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
73.63.Bd Nanocrystalline materials
61.72.uf Ge and Si
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.Cc Kinetics of defect formation and annealing
68.37.Lp Transmission electron microscopy (TEM)

The interface of epitaxial SrTiO3 on silicon: in situ and ex situ studies

Xiaoming Hu, H. Li, Y. Liang, Y. Wei, Z. Yu, D. Marshall, J. Edwards, R. Droopad, X. Zhang, A. A. Demkov, K. Moore, and J. Kulik

Appl. Phys. Lett. 82, 203 (2003); http://dx.doi.org/10.1063/1.1536247 (3 pages) | Cited 44 times

Online Publication Date: 6 January 2003

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The formation of interfacial layers between silicon and the overgrown epitaxial SrTiO3 as a function of the growth temperature has been studied in detail using x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. Models for the chemical compositions and atomic bonding states have been established. With a good understanding of the mechanisms of the interfacial layer formations, the molecular-beam epitaxy growth process can be well controlled to form high-quality, single-crystalline oxide films, as well as a desired interface between the grown oxide and silicon substrate. The epitaxial relationship has been found to be SrTiO3 (001)∥Si(001), and SrTiO3 〈100〉∥Si〈110〉. © 2003 American Institute of Physics.
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68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Ct Interface structure and roughness
68.47.Fg Semiconductor surfaces
81.05.Cy Elemental semiconductors
79.60.Jv Interfaces; heterostructures; nanostructures
79.60.Dp Adsorbed layers and thin films
68.37.Lp Transmission electron microscopy (TEM)

Optimization of cubic GaN growth by metalorganic chemical vapor deposition based on residual strain relaxation

Z. H. Feng, H. Yang, X. H. Zheng, Y. Fu, Y. P. Sun, X. M. Shen, and Y. T. Wang

Appl. Phys. Lett. 82, 206 (2003); http://dx.doi.org/10.1063/1.1536714 (3 pages) | Cited 1 time

Online Publication Date: 6 January 2003

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The reduction of residual strain in cubic GaN growth by inserting a thermoannealing process is investigated. It is found that the epilayer with smaller tensile strain is subject to a wider optimal “growth window.” Based on this process, we obtain the high-quality GaN film of pure cubic phase with the thickness of 4 μm by metalorganic chemical vapor deposition. The photoluminescence spectrum at room temperature shows the thick GaN layer has a near-band emission peak with a full width at half maximum of 42 meV which confirms its high crystal quality, further supported by the x-ray (002) diffraction measurement. A simplified model is demonstrated to interpret this strain effect on the growth process. © 2003 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
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Random spin–orbit coupling and spin relaxation in symmetric quantum wells

E. Ya. Sherman

Appl. Phys. Lett. 82, 209 (2003); http://dx.doi.org/10.1063/1.1533839 (3 pages) | Cited 40 times

Online Publication Date: 6 January 2003

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The effective “spin–orbit” field acting upon spins of carriers in two-dimensional electronic structures (the Rashba field) arises due to the spatial asymmetry of the system. It will be shown in this letter that even in quantum wells with perfectly symmetric environment, a random Rashba field arises due to fluctuations of concentration of dopant ions. The magnitude of the field, its correlation function, and electron spin relaxation rate in this field are presented. © 2003 American Institute of Physics.
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73.21.Fg Quantum wells
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.20.Fz Weak or Anderson localization

Bulk-grain resistivity and positive temperature coefficient of ZnO-based varistors

D. Fernández-Hevia, J. de Frutos, A. C. Caballero, and J. F. Fernández

Appl. Phys. Lett. 82, 212 (2003); http://dx.doi.org/10.1063/1.1534620 (3 pages) | Cited 12 times

Online Publication Date: 6 January 2003

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We analyze the conditions that allow the bulk-grain regions of a polycrystalline semiconductor to be explored through electrical measurements. The temperature dependence of grain resistivity in ZnO varistors (300–430 K) is presented, and a positive temperature coefficient is found. This is consistent with a free-carrier density approaching exhaustion, and an electron mobility controlled mainly by lattice (both optical and acoustical) scattering. No grain conductivity activation energy is to be found above room temperature and, therefore, ac-impedance techniques can be inadequate for the evaluation of grain conductivity and shallow donor activation energy. © 2003 American Institute of Physics.
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84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
85.30.Fg Bulk semiconductor and conductivity oscillation devices (including Hall effect devices, space-charge-limited devices, and Gunn effect devices)
72.80.Ey III-V and II-VI semiconductors

Enhanced low temperature electrical activation of B in Si

Ramki Kalyanaraman, V. C. Venezia, L. Pelaz, T. E. Haynes, H.-J. L. Gossmann, and C. S. Rafferty

Appl. Phys. Lett. 82, 215 (2003); http://dx.doi.org/10.1063/1.1535270 (3 pages) | Cited 11 times

Online Publication Date: 6 January 2003

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The electrical activation of B in n-type epitaxial-Si(100) has been enhanced in the temperature range of 400–800 °C. This enhanced activation was measured for 40 keV, 2×1014 cm−2 dose of B implanted into a vacancy-rich Si region. The vacancy-rich region consists of excess vacancies (Vex) generated by a 2 MeV Si implant in the dose range of 3×1015–10×1015 cm−2. The B activation in vacancy-rich Si is found to be a factor of ∼2.4 larger with up to ∼80% of the B activated as compared to similar B implant and activation anneals carried out in the bulk Si. The dependence of B activation on Vex concentration shows that the active B concentration increases with the Vex concentration. From this dependence it was estimated that at least three vacancies are required to activate an additional B atom. This process is distinctly different from the low temperature activation that occurs during solid-phase epitaxial recrystallization of B-doped amorphous Si as no amorphous Si is produced during any step. This low temperature processing will be advantageous in situations where the epitaxial recrystallization of a doped amorphous Si layer is not possible, for instance in the fabrication of fully depleted Si-on-insulator devices. © 2003 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters

Interface properties of thermally oxidized n-GaN metal–oxide–semiconductor capacitors

Yoshitaka Nakano and Takashi Jimbo

Appl. Phys. Lett. 82, 218 (2003); http://dx.doi.org/10.1063/1.1536029 (3 pages) | Cited 27 times

Online Publication Date: 6 January 2003

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We report on the interface properties of thermally oxidized n-GaN metal–oxide–semiconductor capacitors fabricated on sapphire substrates. 100-nm-thick β-Ga2O3 was grown by dry oxidation at 880 °C for 5 h. From secondary ion mass spectrometry measurements, an intermediate Ga oxynitride layer with graded compositions is clearly observed at the β-Ga2O3/GaN interface. Capacitance–voltage measurements show a deep depletion feature and a low interface state density of ∼ 5.5×1010 eV−1 cm−2. Additionally, no discrete interface traps can be detected by deep-level transient spectroscopic measurements. These results indicate that the surface Fermi level is unpinned at the β-Ga2O3/GaN interface, which may be associated with the presence of the interfacial Ga oxynitride layer. © 2003 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
85.30.Tv Field effect devices
71.55.Eq III-V semiconductors

Proposal for all-electrical measurement of T1 in semiconductors

Igor Žutić, Jaroslav Fabian, and S. Das Sarma

Appl. Phys. Lett. 82, 221 (2003); http://dx.doi.org/10.1063/1.1536270 (3 pages) | Cited 22 times

Online Publication Date: 6 January 2003

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In an inhomogeneously-doped magnetic semiconductor, spin relaxation time T1 can be determined by all-electrical measurements. Nonequilibrium spin injected in a magnetic p–n junction gives rise to the spin-voltaic effect, in which the nonequilibrium spin-induced charge current is very sensitive to T1 and can flow even at no applied bias. It is proposed that T1 can be determined by measuring the I–V characteristics in such a geometry. In a magnetic p–n junction, for which the results can be calculated analytically, it is also possible to extract the g-factor and the degree of injected-carrier spin polarization. © 2003 American Institute of Physics.
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72.25.Dc Spin polarized transport in semiconductors
75.50.Pp Magnetic semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.25.Mk Spin transport through interfaces
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

High-efficiency screen-printed silicon ribbon solar cells by effective defect passivation and rapid thermal processing

Ajeet Rohatgi and Ji-Weon Jeong

Appl. Phys. Lett. 82, 224 (2003); http://dx.doi.org/10.1063/1.1536027 (3 pages) | Cited 11 times

Online Publication Date: 6 January 2003

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A conversion efficiency of 15.9% has been achieved on low-cost edge-defined film-fed grown silicon ribbon solar cells. This represents an improvement over the previously reported efficiencies for silicon ribbon solar cells with manufacturable screen-printed contacts and single layer silicon nitride (SiNx) antireflection coating. Two separate rapid thermal processing cycles with fast ramp-up and cooling rates contributed to the enhancement in cell efficiency. The fast ramp-up rate improved the quality of back surface field and contacts; and a short firing time with a fast cooling rate improved contacts and the SiNx-induced hydrogen passivation of defects, resulting in bulk lifetime enhancement from ∼2 to ∼50 μs. © 2003 American Institute of Physics.
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84.60.Jt Photoelectric conversion
81.65.Rv Passivation
61.72.Cc Kinetics of defect formation and annealing
81.05.Cy Elemental semiconductors

Influence of polarization charges in Al0.4Ga0.6N/GaN barrier varactors

M. Saglam, K. Mutamba, A. Megej, C. Sydlo, H. L. Hartnagel, and I. Daumiller

Appl. Phys. Lett. 82, 227 (2003); http://dx.doi.org/10.1063/1.1537516 (3 pages) | Cited 1 time

Online Publication Date: 6 January 2003

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In this letter, we investigate the influence of polarization charges on the characteristics of metal–organic chemical-vapor-deposition-grown Al0.4Ga0.6N/GaN heterostructure barrier varactors (HBVs). The current–voltage and capacitance–voltage characteristics of the AlGaN/GaN HBVs shift asymmetrically due to the combination of piezoelectric (stress-induced) and spontaneous polarization effects in the barriers. Depending on the polarization of the bias voltage, different values of capacitance modulation, 1.4 for negative bias and 1.1 for positive bias, are observed. The obtained measurement results are supported by a theoretical analysis involving polarization charges at layer interfaces as well as their effect on the barrier height and the width of the depletion region. © 2003 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.At Surface states, band structure, electron density of states
81.05.Ea III-V semiconductors
84.32.Tt Capacitors
85.30.Kk Junction diodes
77.22.Ej Polarization and depolarization
77.65.Ly Strain-induced piezoelectric fields
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