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21 Jul 2008

Volume 93, Issue 3, Articles (03xxxx)

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Appl. Phys. Lett. 93, 031101 (2008); http://dx.doi.org/10.1063/1.2959092 (3 pages)

Di Xu, Kevin P. Chen, Kris Ohlinger, and Yuankun Lin
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Stretched-exponential a-Si:H/c-Si interface recombination decay

Stefaan De Wolf, Sara Olibet, and Christophe Ballif

Appl. Phys. Lett. 93, 032101 (2008); http://dx.doi.org/10.1063/1.2956668 (3 pages) | Cited 25 times

Online Publication Date: 23 July 2008

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The electronic properties of hydrogenated amorphous silicon (a-Si:H) relax following stretched exponentials. This phenomenon was explained in the past by dispersive hydrogen diffusion, or by retrapping included hydrogen motion. In this letter, the authors report that the electronic passivation properties of intrinsic a-Si:H/crystalline silicon (c-Si) interfaces relax following a similar law. Carrier injection dependent a-Si:H/c-Si interface recombination calculations suggest this originates from amphoteric interface state (or Si dangling bond) reduction, rather than from a field effect. These findings underline the similarity between a-Si:H/c-Si interface recombination and the electronic properties of a-Si:H bulk material.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.Rv Passivation
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.25.+i Surface conductivity and carrier phenomena

Bias-controlled spin polarization in quantum wires

T.-M. Chen, A. C. Graham, M. Pepper, I. Farrer, and D. A. Ritchie

Appl. Phys. Lett. 93, 032102 (2008); http://dx.doi.org/10.1063/1.2963478 (3 pages) | Cited 9 times

Online Publication Date: 23 July 2008

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We demonstrate that a source-drain bias creates a fully spin-polarized current as the 0.25(2e2/h) plateau in quantum wires even in zero magnetic field. When a source-drain bias lifts the momentum degeneracy, the dc measurements show that it is possible to achieve a unidirectional ferromagnetic order and this ordered spin array is destroyed once transport in both directions commences. The spin polarization of currents, between full spin polarization and partial spin polarization (or spin degeneracy), is thus simply controlled by source-drain bias and split-gate voltage, something of considerable value for spintronics.
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73.63.Nm Quantum wires
72.25.-b Spin polarized transport

Highly stable amorphous-silicon thin-film transistors on clear plastic

Bahman Hekmatshoar, Kunigunde H. Cherenack, Alex Z. Kattamis, Ke Long, Sigurd Wagner, and James C. Sturm

Appl. Phys. Lett. 93, 032103 (2008); http://dx.doi.org/10.1063/1.2963481 (3 pages) | Cited 16 times

Online Publication Date: 23 July 2008

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Hydrogenated amorphous-silicon (a-Si:H) thin-film transistors (TFTs) have been fabricated on clear plastic with highly stable threshold voltages. When operated at a gate field of 2.5×105 V/cm, the threshold voltage shift extrapolated to only ∼ 1.2 V after ten years. This stability is achieved by a high deposition temperature for the gate silicon nitride insulator which reduces charge trapping and high hydrogen dilution during a-Si:H growth to reduce defect creation in a-Si:H. This gate field of 2.5×105 V/cm is sufficient to drive phosphorescent organic light emitting diodes (OLEDs) at a brightness of 1000 Cd/m2. The half-life of the TFT current is over ten years, slightly longer than the luminescence half-life of high quality green OLEDs.
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85.30.Tv Field effect devices
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
85.60.Jb Light-emitting devices

Evidence of low interface trap density in GeO2/Ge metal-oxide-semiconductor structures fabricated by thermal oxidation

Hiroshi Matsubara, Takashi Sasada, Mitsuru Takenaka, and Shinichi Takagi

Appl. Phys. Lett. 93, 032104 (2008); http://dx.doi.org/10.1063/1.2959731 (3 pages) | Cited 63 times

Online Publication Date: 23 July 2008

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We have fabricated GeO2/Ge metal-oxide-semiconductor (MOS) structures by direct thermal oxidation of Ge substrates. The interface trap density (Dit) of Al/GeO2/Ge MOS structures, measured by the low temperature conductance method including the effect of the surface potential fluctuation, is found to be reduced as the oxidation temperature increases. The minimum values of Dit can be obtained for the oxidation around 575 °C, which is in the maximum temperature range where GeO volatilization does not occur under atmospheric pressure of O2. It is also found that the hydrogen annealing before Al gate formation is effective for the passivation of GeO2/Ge interface states. It is clarified, as a result, that the minimum Dit value lower than 1011 cm−2 eV−1 can be obtained for GeO2/Ge MOS interfaces fabricated by direct oxidation of Ge substrates.
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73.20.-r Electron states at surfaces and interfaces
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc Kinetics of defect formation and annealing
81.65.Mq Oxidation
81.65.Rv Passivation

Metallization contacts to nonpolar a-plane n-type GaN

Hyunsoo Kim, Sung-Nam Lee, Yongjo Park, Joon Seop Kwak, and Tae-Yeon Seong

Appl. Phys. Lett. 93, 032105 (2008); http://dx.doi.org/10.1063/1.2963492 (3 pages) | Cited 16 times

Online Publication Date: 23 July 2008

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We have investigated the electrical characteristics of metallization contacts to nonpolar a-plane and polar c-plane n-type GaN. Pd Schottky diodes and x-ray photoemission spectroscopy measurements show that the Schottky barrier height of the a-plane GaN is lower than that of the c-plane GaN by 0.24 and 0.30 eV, respectively. Ti/Al Ohmic contacts to the a-plane n-GaN produce lower contact resistivity than that of the c-plane samples when annealed at 500 °C. However, Ti/Al contacts to the c-plane and a-plane GaN show opposite electrical behavior when annealed at temperatures above 500 °C, which is attributed to the absence of polarization-induced surface charges for a-plane GaN.
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85.40.Ls Metallization, contacts, interconnects; device isolation
73.40.Ns Metal-nonmetal contacts
79.60.Bm Clean metal, semiconductor, and insulator surfaces
73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.Kk Junction diodes
73.40.Cg Contact resistance, contact potential

Formation of a manganese oxide barrier layer with thermal chemical vapor deposition for advanced large-scale integrated interconnect structure

Koji Neishi, Shiro Aki, Kenji Matsumoto, Hiroshi Sato, Hitoshi Itoh, Shigetoshi Hosaka, and Junichi Koike

Appl. Phys. Lett. 93, 032106 (2008); http://dx.doi.org/10.1063/1.2963984 (3 pages) | Cited 9 times

Online Publication Date: 23 July 2008

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Advanced large-scale integrated interconnect structure faces a major challenge in forming a thin and conformal diffusion barrier layer. We deposited a Mn oxide layer by thermal chemical vapor deposition (CVD) on SiO2 substrates and investigated deposition behavior and diffusion barrier property. A thin Mn oxide layer was formed with a uniform thickness of 2.6–10 nm depending on deposition temperature between 100 and 400 °C. Heat-treated samples of Cu/CVD-Mn oxide/SiO2 indicated no interdiffusion at 400 °C for 100 h. The CVD of the Mn oxide layer was found to be an excellent barrier formation process.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Radiotracer diffusion of cobalt, iron, and chromium in dislocation-free germanium

L. Lerner and N. A. Stolwijk

Appl. Phys. Lett. 93, 032107 (2008); http://dx.doi.org/10.1063/1.2964183 (3 pages) | Cited 2 times

Online Publication Date: 23 July 2008

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Diffusion of the transition metals Co, Fe, and Cr into single-crystal germanium is found to be fast processes at temperatures relevant to the fabrication of semiconductor devices. These results were obtained from experiments in which electronic-grade Ge samples were provided with a radioactive surface source and short time annealed in a lamp furnace at temperatures ranging from 600 to 900 °C. Diffusion coefficients were determined from penetration profiles of the radioisotopes 57Co, 59Fe, and 51Cr. The results are interpreted within the framework of interstititial-substitutional diffusion and compared with earlier diffusion data on Ge crystals.
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66.30.J- Diffusion of impurities
61.72.Cc Kinetics of defect formation and annealing
61.72.jj Interstitials
81.05.Cy Elemental semiconductors

High-temperature annealing behavior of deep levels in 1 MeV electron irradiated p-type 6H-SiC

Giovanni Alfieri and Tsunenobu Kimoto

Appl. Phys. Lett. 93, 032108 (2008); http://dx.doi.org/10.1063/1.2964184 (3 pages) | Cited 1 time

Online Publication Date: 23 July 2008

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We report on the thermal stability of deep levels detected after 1 MeV electron irradiated p-type 6H-SiC. The investigation was performed by deep level transient spectroscopy, and an isochronal annealing series was carried out in the 373–2073 K temperature range. We found seven traps located between 0.23 and 1.3 eV above the valence band edge (EV). Two traps anneal out at temperatures below 1273 K, while the others display a high thermal stability up to 2073 K. The nature of the detected traps is discussed on the basis of their annealing behavior and previous data found in the literature.
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71.55.Ht Other nonmetals
73.20.At Surface states, band structure, electron density of states
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments

Ti/Al/Mo/Au Ohmic contacts to all-binary AlN/GaN high electron mobility transistors

Liang Wang, Ilesanmi Adesida, Amir M. Dabiran, Andrew M. Wowchak, and Peter P. Chow

Appl. Phys. Lett. 93, 032109 (2008); http://dx.doi.org/10.1063/1.2964204 (3 pages) | Cited 3 times

Online Publication Date: 23 July 2008

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Electrical and microstructural characterizations of the Ti/Al/Mo/Au Ohmic contacts to ultrathin AlN/GaN heterostructures were carried out. It was found that as-deposited contacts had linear I-V behavior due to high tunneling current across the thin AlN barrier. A contact resistance of 0.455 Ω mm was obtained for samples annealed at 800 °C without any premetallization plasma treatment. Transmission electron microscopy studies showed that despite the use of Ti, the AlN layer remained intact. Mushroom-shaped TiN protrusions were formed only along threading dislocations, which terminated in the AlN layer. The TiN protrusions acted as metal plugs/spikes thereby aiding carrier transport.
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85.30.Tv Field effect devices
85.75.Hh Spin polarized field effect transistors

Isotope disorder of phonons in GaN and its beneficial effect on high power field effect transistors

Jacob B. Khurgin, Debdeep Jena, and Yujie J. Ding

Appl. Phys. Lett. 93, 032110 (2008); http://dx.doi.org/10.1063/1.2961120 (3 pages) | Cited 2 times

Online Publication Date: 23 July 2008

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We analyze the influence of isotope disorder on longitudinal optical (LO) phonon modes in GaN and then study the scattering by disordered LO phonons in the channel of high power transistor. Results indicate that as a larger number of LO phonons gets excited, a more efficient cooling of electrons can be accomplished and most of the spurious hot phonon effects can be mitigated leading to significant improvement in the saturation velocity. To the best of our knowledge this is the first ever example of disorder playing constructive role in the performance of room-temperature electronic devices.
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85.30.Tv Field effect devices

Studies on the Bi/Si(100)−(2×1) interface

A. Bannani, C. A. Bobisch, and R. Möller

Appl. Phys. Lett. 93, 032111 (2008); http://dx.doi.org/10.1063/1.2963031 (3 pages) | Cited 4 times

Online Publication Date: 25 July 2008

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Epitaxial Bi(111) films on the Si(100)−(2×1) surface were studied by two different scanning probe techniques, to obtain information on the buried interface. Ballistic electron emission microscopy reveals that the transmission across the Schottky barrier depends on the type of substrate terrace. The thermovoltage in scanning tunneling microscopy exhibits alternating signals for substrate step edges, which can be related to SA and SB steps, characteristic for the uncovered Si(100)−(2×1) surface. In addition to information about the growth mode of Bi, it was found that typical features of the Si(100)−(2×1) surface reconstruction are maintained.
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68.35.bg Semiconductors
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts

Repeated epitaxial growth and transfer of arrays of patterned, vertically aligned, crystalline Si wires from a single Si(111) substrate

Joshua M. Spurgeon, Katherine E. Plass, Brendan M. Kayes, Bruce S. Brunschwig, Harry A. Atwater, and Nathan S. Lewis

Appl. Phys. Lett. 93, 032112 (2008); http://dx.doi.org/10.1063/1.2959184 (3 pages) | Cited 19 times

Online Publication Date: 25 July 2008

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Multiple arrays of Si wires were sequentially grown and transferred into a flexible polymer film from a single Si(111) wafer. After growth from a patterned, oxide-coated substrate, the wires were embedded in a polymer and then mechanically separated from the substrate, preserving the array structure in the film. The wire stubs that remained were selectively etched from the Si(111) surface to regenerate the patterned substrate. Then the growth catalyst was electrodeposited into the holes in the patterned oxide. Cycling through this set of steps allowed regrowth and polymer film transfer of several wire arrays from a single Si wafer.
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81.05.Cy Elemental semiconductors
81.07.Vb Quantum wires
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

p-channel thin-film transistor using p-type oxide semiconductor, SnO

Yoichi Ogo, Hidenori Hiramatsu, Kenji Nomura, Hiroshi Yanagi, Toshio Kamiya, Masahiro Hirano, and Hideo Hosono

Appl. Phys. Lett. 93, 032113 (2008); http://dx.doi.org/10.1063/1.2964197 (3 pages) | Cited 62 times

Online Publication Date: 25 July 2008

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This paper reports that among known p-type oxide semiconductors, tin monoxide (SnO) has a high hole mobility and produces good p-type oxide thin-film transistors (TFTs). Device-quality SnO films were grown epitaxially on (001) yttria-stabilized zirconia substrates at 575 °C by pulsed laser deposition. These exhibited a Hall mobility of 2.4 cm2 V−1 s−1 at room temperature. Top-gated TFTs, using epitaxial SnO channels, exhibited field-effect mobilities of 1.3 cm2 V−1 s−1, on/off current ratios of ∼ 102, and threshold voltages of 4.8 V.
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85.30.Tv Field effect devices
81.15.Fg Pulsed laser ablation deposition

Effects of the compensation level on the carrier lifetime of crystalline silicon

S. Dubois, N. Enjalbert, and J. P. Garandet

Appl. Phys. Lett. 93, 032114 (2008); http://dx.doi.org/10.1063/1.2961030 (3 pages) | Cited 16 times

Online Publication Date: 25 July 2008

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This study focuses on the evolution of the carrier lifetime with the compensation level in crystalline silicon. Especially we show that an increase in the compensation level reduces the recombination strength of doping species and of some metal impurities. These theoretical results are confirmed by the chemical and electrical characterizations of strongly compensated multicrystalline silicon wafers. These results are of paramount importance since an accurate control of the compensation level can lead to strong improvements in silicon solar cells efficiencies.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors
61.72.uf Ge and Si
61.72.sd Impurity concentration
81.05.Cy Elemental semiconductors
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