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18 Jul 2005

Volume 87, Issue 3, Articles (03xxxx)

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Appl. Phys. Lett. 87, 033501 (2005); http://dx.doi.org/10.1063/1.1992665 (3 pages)

Yoshihito Miyoshi, Fumito Nakajima, Junichi Motohisa, and Takashi Fukui
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Influence of Mg content on the band alignment at CdS/(Zn,Mg)O interfaces

G. Venkata Rao, F. Säuberlich, and A. Klein

Appl. Phys. Lett. 87, 032101 (2005); http://dx.doi.org/10.1063/1.1995951 (3 pages) | Cited 22 times

Online Publication Date: 11 July 2005

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In this investigation, we studied electronic properties of the CdS/Zn1−xMgxO (x = 0,0.15) interface using photoelectron spectroscopy. ZnO and (Zn,Mg)O films were deposited by magnetron sputtering from ceramic targets on thermally evaporated CdS. Valence-band offsets of ΔEV = 1.2±0.1 eV are determined for both interfaces. The gap difference of 0.3 eV between ZnO and Zn0.85Mg0.15O is therefore fully accommodated by a different conduction-band energy, which should be well suited for modulation doping in ZnO/(Zn,Mg)O heterostructures.
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73.20.At Surface states, band structure, electron density of states
71.20.Nr Semiconductor compounds
61.72.S- Impurities in crystals
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.66.Hf II-VI semiconductors

Band gap and band offset of (GaIn)(PSb) lattice matched to InP

F. Köhler, G. Böhm, R. Meyer, and M.-C. Amann

Appl. Phys. Lett. 87, 032102 (2005); http://dx.doi.org/10.1063/1.1996847 (3 pages) | Cited 2 times

Online Publication Date: 12 July 2005

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Metastable (GaxIn1−x)(PySb1−y) layers were grown on (001) InP substrates by gas source molecular beam epitaxy. Low-temperature photoluminescence spectroscopy was applied to these heterostructures and revealed spatially indirect band-to-band recombination of electrons localized in the InP with holes in the (GaxIn1−x)(PySb1−y). In addition, samples with layer thicknesses larger than 100 nm showed direct PL across the band gap of (GaxIn1−x)(PySb1−y). Band-gap energies and band offset energies of (GaxIn1−x)(PySb1−y) relative to InP were derived from these PL data. A strong bowing parameter was observed.
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73.20.At Surface states, band structure, electron density of states
81.05.Ea III-V semiconductors
71.20.Nr Semiconductor compounds
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Hole drift-mobility measurements in microcrystalline silicon

T. Dylla, F. Finger, and E. A. Schiff

Appl. Phys. Lett. 87, 032103 (2005); http://dx.doi.org/10.1063/1.1984087 (3 pages) | Cited 19 times

Online Publication Date: 12 July 2005

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We have measured transient photocurrents on several p‐i‐n solar cells based on microcrystalline silicon. For two of these samples, we were able to obtain conclusive hole drift-mobility measurements. Despite the predominant crystallinity of these samples, temperature-dependent measurements were consistent with an exponential-bandtail trapping model for transport, which is usually associated with noncrystalline materials. We estimated valence bandtail widths of about 31 meV and hole band mobilities of 1–2 cm2/V s. The measurements support mobility-edge transport for holes in these microcrystalline materials, and broaden the range of materials for which mobility-edge transport corresponds to an apparently universal band mobility of order 1 cm2/V s.
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84.60.Jt Photoelectric conversion
73.61.Cw Elemental semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.50.Dn Low-field transport and mobility; piezoresistance
71.20.Mq Elemental semiconductors

Infrared capacity mapping of semiconductor junctions by lock-in thermography

Peter Pohl and Rolf Brendel

Appl. Phys. Lett. 87, 032104 (2005); http://dx.doi.org/10.1063/1.1999010 (3 pages) | Cited 1 time

Online Publication Date: 12 July 2005

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We image the reverse-bias-modulated space charges in a heated p-n junction using infrared (IR) lock-in thermography. The modulation of the space charges leads to a change of the free carrier IR emission signal of the sample, which is detected by an IR camera. This way charge carrier densities are measured, which in combination with the voltage applied yield the capacitance of the junction. Experimentally measured capacitance-voltage curves agree with the theoretical model of an abrupt p-n junction. Using lock-in thermography, we deduce the spatially resolved acceptor doping concentration of a crystalline silicon wafer. A sensitivity analysis shows that our system detects a noise equivalent capacitance of 1 nF cm−2 after a measurement period of 28 min at a lateral resolution of 170 μm.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.68.+m Photography, photographic instruments; xerography
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.-i Conductivity phenomena in semiconductors and insulators
61.72.S- Impurities in crystals

Super-Poissonian shot noise in the resonant tunneling due to coupling with a localized level

Ivana Djuric, Bing Dong, and H. L. Cui

Appl. Phys. Lett. 87, 032105 (2005); http://dx.doi.org/10.1063/1.1999020 (3 pages) | Cited 28 times

Online Publication Date: 12 July 2005

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We report our studies of the shot noise spectrum in tunneling through an interacting quantum dot when an additional single-level quantum dot without tunnel coupling to leads is coherently side connected to it. We show that the zero-frequency shot noise could reach a super-Poissonian value for appropriate ratios between dot-dot hoppings and dot-lead couplings, but the current is independent on the hopping. Moreover, the frequency spectrum of shot noise shows an obvious peak at the Rabi frequency, which is controllable by tuning the dot-lead couplings.
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73.63.Kv Quantum dots
72.70.+m Noise processes and phenomena
73.40.Gk Tunneling
73.23.Hk Coulomb blockade; single-electron tunneling

Evidence of interface-induced persistent photoconductivity in InP/In0.53Ga0.47As/InP double heterostructures grown by molecular-beam epitaxy

M. K. Hudait, Y. Lin, S. H. Goss, P. Smith, S. Bradley, L. J. Brillson, S. W. Johnston, R. K. Ahrenkiel, and S. A. Ringel

Appl. Phys. Lett. 87, 032106 (2005); http://dx.doi.org/10.1063/1.1994948 (3 pages) | Cited 1 time

Online Publication Date: 12 July 2005

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The impact of interface switching sequences on interface quality and minority carrier recombination in In0.53Ga0.47As/InP double heterostructure (DH) grown by solid-source molecular-beam epitaxy (MBE) was studied. As2 exposure at the lower In0.53Ga0.47As/InP interface prior to In0.53Ga0.47As growth was found to cause enhanced As diffusion into the underlying InP that correlates with steadily increased photoconductive decay (PCD) lifetimes beyond the theoretical radiative and Auger limit. Low-temperature PCD measurements reveal that a persistent photoconductivity (PPC) process is responsible for the high “apparent” lifetimes. The PPC effect increases monotonically with As2 exposure on the InP surface, implying the involvement of interfacial defects in the carrier recombination dynamics of In0.53Ga0.47As/InP DHs grown by MBE.
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81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Pz Photoconduction and photovoltaic effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
66.30.-h Diffusion in solids

Interface traps and dangling-bond defects in (100)Ge/HfO2

V. V. Afanas’ev, Y. G. Fedorenko, and A. Stesmans

Appl. Phys. Lett. 87, 032107 (2005); http://dx.doi.org/10.1063/1.1947372 (3 pages) | Cited 62 times

Online Publication Date: 13 July 2005

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Combined electrical and electron spin resonance analysis reveals dramatic differences in the interface defect properties of the (100)Ge/GeOxNy/HfO2 and (100)Ge/GeO2 interfaces from the seemingly similar interfaces of (100)Si with the HfO2 and SiO2. No dangling bond centers associated with Ge crystal surface atoms are detected. Only paramagnetic defects in the near-interfacial Ge oxide or Ge (oxy)nitride layers are observed. In contrast to the amphoteric traps related to the dangling bonds (Pb-type centers) commonly observed at the silicon/insulator interfaces, the major component of the Ge/insulator interface trap spectrum comes from slow acceptor states which show no correlation with paramagnetic centers and are resistant to passivation by hydrogen.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.55.Ht Other nonmetals
76.30.Mi Color centers and other defects

Investigation of metal diffusion into polymers by ab initio molecular dynamics

Ling Dai, Shuo-Wang Yang, Xian-Tong Chen, Ping Wu, and V. B. C. Tan

Appl. Phys. Lett. 87, 032108 (2005); http://dx.doi.org/10.1063/1.1996840 (3 pages) | Cited 4 times

Online Publication Date: 14 July 2005

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Ab initio molecular dynamics simulations were performed to study the motion of single metal atoms and atom clusters of Cu and Ta in SiLK-like polymers to gain an insight into their diffusion mechanisms and characteristics. The analysis suggests that Cu atom motions are largely affected by jumps between cavities inside the polymer and that Ta is more sluggish than Cu not only because of its larger mass but also because of stronger affinity to the polymers. It was also found that crosslinking within polymers of the same density does not significantly affect the motions of the metal atoms or clusters.
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66.30.J- Diffusion of impurities
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Quantitative copper measurement in oxidized p-type silicon wafers using microwave photoconductivity decay

H. Väinölä, E. Saarnilehto, M. Yli-Koski, A. Haarahiltunen, J. Sinkkonen, G. Berenyi, and T. Pavelka

Appl. Phys. Lett. 87, 032109 (2005); http://dx.doi.org/10.1063/1.1999008 (3 pages) | Cited 3 times

Online Publication Date: 15 July 2005

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We propose a method to measure trace copper contamination in p-type silicon using the microwave photoconductivity decay (μ-PCD) technique. The method is based on the precipitation of interstitial copper, activated by high-intensity light, which results in enhanced minority carrier recombination activity. We show that there is a quantitative correlation between the enhanced recombination rate and the Cu concentration by comparing μ-PCD measurements with transient ion drift and total reflection x-ray fluorescence measurements. The results indicate that the method is capable of measuring Cu concentrations down to 1010 cm−3. There are no limitations to wafer storage time if corona charge is used on the oxidized wafer surfaces as the charge prevents copper outdiffusion. We briefly discuss the role of oxide precipitates both in the copper precipitation and in the charge carrier recombination processes.
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81.05.Cy Elemental semiconductors
72.40.+w Photoconduction and photovoltaic effects
72.30.+q High-frequency effects; plasma effects
81.65.Mq Oxidation
61.72.J- Point defects and defect clusters
81.30.Mh Solid-phase precipitation
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
68.35.Fx Diffusion; interface formation
68.35.Dv Composition, segregation; defects and impurities

Atomistic study of GaN surface grown on Si(111)

Z. T. Wang, Y. Yamada-Takamura, Y. Fujikawa, T. Sakurai, and Q. K. Xue

Appl. Phys. Lett. 87, 032110 (2005); http://dx.doi.org/10.1063/1.2000332 (3 pages) | Cited 7 times

Online Publication Date: 15 July 2005

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GaN is directly grown on Si(111) by radio-frequency plasma-assisted molecular-beam epitaxy, and the surface is studied using in situ reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). By optimizing the growth condition, well-defined surface reconstructions are observed in atomically-resolved STM images after the additional Ga deposition, indicating the uniform N-polarity of the grown film. We show that N-rich condition in the initial GaN growth and slightly Ga-rich condition in the subsequent growth are critical in order to achieve monopolar uniform GaN films.
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81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.A- Nucleation and growth
68.47.Fg Semiconductor surfaces

Titanium-doped indium oxide: A high-mobility transparent conductor

M. F. A. M. van Hest, M. S. Dabney, J. D. Perkins, D. S. Ginley, and M. P. Taylor

Appl. Phys. Lett. 87, 032111 (2005); http://dx.doi.org/10.1063/1.1995957 (3 pages) | Cited 43 times

Online Publication Date: 15 July 2005

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We report on the effects of titanium doping (0–7 at. %) on the optical and electrical properties of In2O3 using combinatorial deposition and analysis techniques. Maximum mobilities are observed at Ti concentrations of 1.5–2.5 at. % and are >80 cm2/V s in sputtered films. The carrier concentration increased with titanium content to a high of 8.0×1020 cm−3. Data show that one carrier is generated per added Ti between 1 and 3 at. %. Conductivities up to 6260 Ω−1 cm−1 were observed. These remained very high >5000 Ω−1 cm−1 across a wide compositional range. The optical transparency is high (>85%) in a wide spectral range from 400 nm to at least 1750 nm. The work function of titanium-doped indium oxide varies substantially over the studied compositional range.
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81.05.Hd Other semiconductors
61.72.up Other materials
78.66.Li Other semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
72.20.Fr Low-field transport and mobility; piezoresistance
73.61.Le Other inorganic semiconductors
73.30.+y Surface double layers, Schottky barriers, and work functions
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