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25 Dec 2006

Volume 89, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 89, 263110 (2006); http://dx.doi.org/10.1063/1.2424541 (3 pages)

Ch. Deneke, U. Zschieschang, H. Klauk, and O. G. Schmidt
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Subpicosecond time-resolved Raman studies of field-induced transient transport in an InxGa1−xAs-based p-i-n semiconductor nanostructure

K. T. Tsen, Juliann G. Kiang, D. K. Ferry, and H. Morkoç

Appl. Phys. Lett. 89, 262101 (2006); http://dx.doi.org/10.1063/1.2420782 (3 pages) | Cited 1 time

Online Publication Date: 26 December 2006

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Electron transient transport in an InxGa1−xAs-based (x = 0.53) p-i-n nanostructure under the application of an electric field has been studied by time-resolved Raman spectroscopy on a subpicosecond time scale and at T = 300 K. The experimental results reveal the time evolution of the electron distribution function and electron drift velocity with subpicosecond time resolution. These experimental results are compared with those of both InP-based and GaAs-based p-i-n nanostructures and provide a consistent understanding and better insight of electron transient transport phenomena in semiconductors.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.63.-b Electronic transport in nanoscale materials and structures
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.30.Fs III-V and II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics

Electron transport in naphthylamine-based organic compounds

S. C. Tse, K. C. Kwok, and S. K. So

Appl. Phys. Lett. 89, 262102 (2006); http://dx.doi.org/10.1063/1.2420785 (3 pages) | Cited 50 times

Online Publication Date: 26 December 2006

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Two naphthylamine-based hole transporters, namely, N,N′-diphenyl-N,N′-bis(1-naphthyl)(1,1′-biphenyl)-4,4′diamine (NPB) and 4,4′,4″-tris(n-(2-naphthyl)-n-phenyl-amino)-triphenylamine (2TNATA), were found to possess electron transporting (ET) abilities. From time-of-flight measurements, values of electron mobilities for NPB and 2TNATA are (6–9)×10−4 and (1–3)×10−4 cm2/V s, respectively, under an applied electric field range of 0.04–0.8 MV/cm at 290 K. An organic light-emitting diode that employed NPB as the ET material was demonstrated. The electron conducting mechanism of NPB and 2TNATA in relation to the Marcus theory [ Rev. Mod. Phys. 65, 599 (1993) ] from quantum chemistry will be discussed.
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72.20.Ee Mobility edges; hopping transport
72.80.Le Polymers; organic compounds (including organic semiconductors)
85.60.Jb Light-emitting devices

Selective epitaxial growth of 4H-SiC at reduced temperatures using halo-carbon precursor

Bharat Krishnan, Hrishikesh Das, Huang-De Lin, and Yaroslav Koshka

Appl. Phys. Lett. 89, 262103 (2006); http://dx.doi.org/10.1063/1.2423323 (3 pages) | Cited 2 times

Online Publication Date: 26 December 2006

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Selective homoepitaxial growth of 4H-SiC polytype at temperatures down to 1300 °C was investigated using novel halo-carbon epitaxial growth technique. More than three times higher growth rate than in blanket epitaxy without morphology degradation was due to the local loading effect, which demonstrated that the growth rate of SiC homoepitaxy at low temperatures is limited by the gas-phase reaction mechanisms rather than surface mechanisms. It was established that the step-flow growth without undesirable nucleation may be maintained at growth rates in excess of 6 μm/h. Strong dependence of the growth rate on the ratio of the seed area to the masked area indicated that the growth rate is predominantly mass transport limited. Facet formation and conditions for suppressing defect generation at the mesa walls were investigated.
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68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Strong magnetic scattering from TiOx adhesion layers

A. Trionfi, S. Lee, and D. Natelson

Appl. Phys. Lett. 89, 262104 (2006); http://dx.doi.org/10.1063/1.2423327 (3 pages) | Cited 2 times

Online Publication Date: 26 December 2006

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Electronic phase coherence in normal metals is incredibly sensitive to magnetic scattering. As a result, the weak localization magnetoresistance and time-dependent universal conductance fluctuations are powerful probes of magnetic impurities. The authors report measurements of these effects in Au and Ag nanowires with a 1.5 nm thick Ti adhesion layer underneath the deposited metal. The results indicate an anomalously large magnetic impurity concentration due to the Ti layer. The results also suggest that this magnetic scattering and its evolution are related to the oxidation state of the Ti.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
75.30.Hx Magnetic impurity interactions

Defect reduction in (11math0) a-plane GaN by two-stage epitaxial lateral overgrowth

X. Ni, Ü. Özgür, Y. Fu, N. Biyikli, J. Xie, A. A. Baski, H. Morkoç, and Z. Liliental-Weber

Appl. Phys. Lett. 89, 262105 (2006); http://dx.doi.org/10.1063/1.2423328 (3 pages) | Cited 23 times

Online Publication Date: 26 December 2006

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The authors report a two-stage epitaxial lateral overgrowth (ELO) method to get uniformly coalesced (11math0) a-plane GaN using metal organic chemical vapor deposition by employing a relatively lower growth temperature in the first stage followed by conditions leading to enhanced lateral growth in the second. Using a two-stage ELO method the average Ga-polar to N-polar wing growth rate ratio has been reduced from 4–6 to 1.5–2, which consequently reduced the height difference between the two approaching wings at the coalescence front that resulted from the wing tilt (0.44° for Ga and 0.37° for N wings, measured by x-ray diffraction), thereby making their coalescence much easier. Transmission electron microscopy showed that the threading dislocation density in the wing areas was 1.0×108 cm−2, more than two orders of magnitude lower than that in the window areas (4.2×1010 cm−2). However, high density of basal stacking faults of 1.2×104 cm−1 was still present in the wing areas as compared to c-plane GaN where they are rarely observed away from the substrate. Atomic force microscopy and photoluminescence measurements on the coalesced ELO a-plane GaN sample also indicated improved material quality.
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68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Investigation of void nucleation and propagation during electromigration of flip-chip solder joints using x-ray microscopy

S. H. Chiu and Chih Chen

Appl. Phys. Lett. 89, 262106 (2006); http://dx.doi.org/10.1063/1.2425040 (3 pages) | Cited 5 times

Online Publication Date: 27 December 2006

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X-ray microscopy was employed to investigate void nucleation and propagation during electromigration in solder joints. The shape of the voids at various stages can be clearly observed. The voids became irregular when they propagated to deplete the contact opening. Growth velocity at the early stage was found to be 1.3 μm/h under 6.5×103 A/cm2 at 150 °C, and it decreased to 0.3 μm/h at later stages. Formation of intermetallic compound (IMC) and compositional changes at the interface of solder/IMC on the chip side were attributed to the retarded growth rate at later stages.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration

Carrier concentration induced band-gap shift in Al-doped Zn1−xMgxO thin films

J. G. Lu, S. Fujita, T. Kawaharamura, H. Nishinaka, Y. Kamada, and T. Ohshima

Appl. Phys. Lett. 89, 262107 (2006); http://dx.doi.org/10.1063/1.2424308 (3 pages) | Cited 17 times

Online Publication Date: 27 December 2006

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Transparent conducting Al-doped Zn1−xMgxO thin films were grown on glass substrates by chemical vapor deposition. The resistivity could be lowered to 10−3 Ω cm with optical transmittance above 85% in visible regions. The influence of carrier concentration on band-gap shift in Zn1−xMgxO alloys was systematically studied. The shift of energy gap could be fully explained by the Fermi-level band filling and band-gap renormalization effects. As the Mg content increased, the electron effective masses in Zn1−xMgxO (x = 0–0.21) alloys increased from 0.30m0 to 0.49m0. The Al-doping efficiency was reduced with the increase in alloy composition.
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73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.20.Ps Other inorganic compounds
61.72.up Other materials

Control of structure, conduction behavior, and band gap of Zn1−xMgxO films by nitrogen partial pressure ratio of sputtering gases

C. X. Cong, B. Yao, G. Z. Xing, Y. P. Xie, L. X. Guan, B. H. Li, X. H. Wang, Z. P. Wei, Z. Z. Zhang, Y. M. Lv, D. Z. Shen, and X. W. Fan

Appl. Phys. Lett. 89, 262108 (2006); http://dx.doi.org/10.1063/1.2424449 (3 pages) | Cited 12 times

Online Publication Date: 27 December 2006

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Zn1−xMgxO films were grown by radio-frequency reactive magnetron sputtering using mixture of nitrogen and argon as sputtering gases. It was found that Mg concentration, structures, electrical properties, and band gaps of the films can be tuned by changing nitrogen partial pressure ratio of the sputtering gases. The Zn1−xMgxO film consists of wurtzite phase at the ratios from 0% to 50%, mixture of wurtzite and cubic phases at the ratios of 78% to 83%, and cubic phase at 100%. The Mg concentration increased linearly with increasing the ratio. The band gap increases from 3.64 eV at x = 0.172 to 4.02 eV at x = 0.44 for the wurtzite Zn1−xMgxO and reaches 6.30 eV for cubic Zn1−xMgxO with x = 0.84. All the as-grown Zn1−xMgxO films show high resistivity at room temperature, but transform into p-type conduction after annealing at 600 °C for 30 min under 10−4 Pa, except for the film grown at the ratio of zero.
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68.55.-a Thin film structure and morphology
73.61.Ga II-VI semiconductors
71.20.Nr Semiconductor compounds
81.15.Cd Deposition by sputtering
61.66.Bi Elemental solids
61.66.Dk Alloys
61.72.Cc Kinetics of defect formation and annealing

Experimental study of the subwavelength imaging by a wire medium slab

Pavel A. Belov, Yan Zhao, Sunil Sudhakaran, Akram Alomainy, and Yang Hao

Appl. Phys. Lett. 89, 262109 (2006); http://dx.doi.org/10.1063/1.2424557 (3 pages) | Cited 17 times

Online Publication Date: 27 December 2006

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An experimental investigation of subwavelength imaging by a wire medium slab is performed. A complex-shaped near field source is used in order to test imaging performance of the device. It is demonstrated that the ultimate bandwidth of operation of the constructed imaging device is 4.5% that coincides with theoretical predictions [ P. A. Belov and M. G. Silveirinha, Phys. Rev. E 73, 056607 (2006) ]. Within this band the wire medium slab is capable of transmitting images with λ/15 resolution irrespective of the shape and complexity of the source. Actual bandwidth of operation for particular near-field sources can be larger than the ultimate value, but it strongly depends on the configuration of the source.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.-a Optical materials
07.60.-j Optical instruments and equipment

True dipole at the indium tin oxide/organic semiconductor interface

Yow-Jon Lin, Jia-huang Hong, Yi-Chun Lien, and Bei-Yuan Liu

Appl. Phys. Lett. 89, 262110 (2006); http://dx.doi.org/10.1063/1.2424646 (3 pages) | Cited 3 times

Online Publication Date: 28 December 2006

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There has been long-standing interest in the development of organic optoelectronic devices. However, the authors find that the previously reported interface-dipole calculations seem to be inaccurate, owing to a persistent neglect of the induced band bending of indium tin oxide (ITO) by coating of organic semiconductors on ITO. In this study, the correlation between the induced band bending of ITO in the presence of organic semiconductors on ITO and the dipole at the interface was examined.
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73.20.At Surface states, band structure, electron density of states
73.30.+y Surface double layers, Schottky barriers, and work functions
79.60.Jv Interfaces; heterostructures; nanostructures
61.50.Lt Crystal binding; cohesive energy

Effect of grain alignment on interface trap density of thermally oxidized aligned-crystalline silicon films

Woong Choi, Jung-Kun Lee, and Alp T. Findikoglu

Appl. Phys. Lett. 89, 262111 (2006); http://dx.doi.org/10.1063/1.2424655 (3 pages)

Online Publication Date: 28 December 2006

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The authors report studies of the effect of grain alignment on interface trap density of thermally oxidized aligned-crystalline silicon (ACSi) films by means of capacitance-voltage (C-V) measurements. C-V curves were measured on metal-oxide-semiconductor (MOS) capacitors fabricated on ⟨001⟩-oriented ACSi films on polycrystalline substrates. From high-frequency C-V curves, the authors calculated a decrease of interface trap density from 2×1012 to 1×1011 cm−2 eV−1 as the grain mosaic spread in ACSi films improved from 13.7° to 6.5°. These results demonstrate the effectiveness of grain alignment as a process technique to achieve significantly enhanced performance in small-grained ( ⩽ 1 μm) polycrystalline Si MOS-type devices.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors

Identification of oxygen and zinc vacancy optical signals in ZnO

T. Moe Børseth, B. G. Svensson, A. Yu. Kuznetsov, P. Klason, Q. X. Zhao, and M. Willander

Appl. Phys. Lett. 89, 262112 (2006); http://dx.doi.org/10.1063/1.2424641 (3 pages) | Cited 115 times

Online Publication Date: 28 December 2006

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Photoluminescence spectroscopy has been used to study single crystalline ZnO samples systematically annealed in inert, Zn-rich and O-rich atmospheres. A striking correlation is observed between the choice of annealing ambient and the position of the deep band emission (DBE) often detected in ZnO. In particular, annealing in O2 results in a DBE at 2.35±0.05 eV, whereas annealing in the presence of metallic Zn results in DBE at 2.53±0.05 eV. The authors attribute the former band to zinc vacancy (VZn) related defects and the latter to oxygen vacancy (VO) related defects. Additional confirmation for the VO and VZn peak identification comes from the observation that the effect is reversible when O- and Zn-rich annealing conditions are switched. After annealing in the presence of ZnO powder, there is no indication for the VZn- or VO-related bands, but the authors observe a low intensity yellow luminescence band peaking at 2.17 eV, probably related to Li, a common impurity in hydrothermally grown ZnO.
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78.55.Et II-VI semiconductors
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing

Adjustable metal-semiconductor transition of FeS thin films by thermal annealing

Ganhua Fu, Angelika Polity, Niklas Volbers, Bruno K. Meyer, Boris Mogwitz, and Jürgen Janek

Appl. Phys. Lett. 89, 262113 (2006); http://dx.doi.org/10.1063/1.2424663 (3 pages) | Cited 1 time

Online Publication Date: 28 December 2006

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FeS polycrystalline thin films were prepared on float glass at 500 °C by radio-frequency reactive sputtering. The influence of vacuum annealing on the metal-semiconductor transition of FeS films was investigated. It has been found that with the increase of the annealing temperature from 360 to 600 °C, the metal-semiconductor transition temperature of FeS films first decreases and then increases, associated with first a reduction and then an enhancement of hysteresis width. The thermal stress is considered to give rise to the abnormal change of the metal-semiconductor transition of the FeS film during annealing.
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73.61.Ng Insulators
81.15.Cd Deposition by sputtering
71.30.+h Metal-insulator transitions and other electronic transitions
81.40.Gh Other heat and thermomechanical treatments
68.60.Bs Mechanical and acoustical properties
68.55.A- Nucleation and growth

Enhanced charge mobility in a molecular hole transporter via addition of redox inactive ionic dopant: Implication to dye-sensitized solar cells

Henry J. Snaith and Michael Grätzel

Appl. Phys. Lett. 89, 262114 (2006); http://dx.doi.org/10.1063/1.2424552 (3 pages) | Cited 35 times

Online Publication Date: 28 December 2006

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Upon the addition of lithium salts to the hole-transporter matrix, 2,2′,7,7′-tetrakis(N,N-di-p-methoxypheny-amine)-9,9′-spirobifluorene (spiro-MeOTAD), the authors observe a 100-fold increase in conductivity through spiro-MeOTAD within a TiO2 mesoporous network. The authors demonstrate this to be a bulk effect and not due to improved injection at the electrodes. By testing “hole-only” diodes of pure spiro-MeOTAD and those doped with lithium salts, the authors calculate that the hole mobility increases from 1.6×10−4 to 1.6×10−3 cm2/V s. The authors discuss the possible mechanisms for this significant enhancement in charge mobility and its implication to the dye-sensitized solar cell operation.
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73.61.Ph Polymers; organic compounds
73.50.Dn Low-field transport and mobility; piezoresistance
72.20.Fr Low-field transport and mobility; piezoresistance
61.72.up Other materials
85.30.Kk Junction diodes
84.60.Jt Photoelectric conversion

Formation mechanism of cerium oxide-doped indium oxide/Ag Ohmic contacts on p-type GaN

Dong-Seok Leem, Tae-Wook Kim, Takhee Lee, Ja-Soon Jang, Young-Woo Ok, and Tae-Yeon Seong

Appl. Phys. Lett. 89, 262115 (2006); http://dx.doi.org/10.1063/1.2424660 (3 pages) | Cited 5 times

Online Publication Date: 28 December 2006

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The authors report on the formation of cerium oxide-doped indium oxide(2.5 nm)/Ag(250 nm) contacts to p-GaN. The contacts become Ohmic with a specific contact resistance of 3.42×10−4 Ω cm2 upon annealing at 530 °C in air. X-ray photoemission spectroscopy (XPS) Ga 3d core levels obtained from the interface regions before and after annealing indicate a large band bending of p-GaN (about 1.7–1.8 eV), namely, an increase of Schottky barrier height. Based on the XPS, secondary ion mass spectroscopy, and capacitance-voltage data, possible transport mechanisms for the annealed contacts are described and discussed.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
61.72.Cc Kinetics of defect formation and annealing
79.60.Jv Interfaces; heterostructures; nanostructures
73.30.+y Surface double layers, Schottky barriers, and work functions
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Quantitative observation and discrimination of AlGaN- and GaN-related deep levels in AlGaN/GaN heterostructures using capacitance deep level optical spectroscopy

A. Armstrong, A. Chakraborty, J. S. Speck, S. P. DenBaars, U. K. Mishra, and S. A. Ringel

Appl. Phys. Lett. 89, 262116 (2006); http://dx.doi.org/10.1063/1.2424670 (3 pages) | Cited 16 times

Online Publication Date: 28 December 2006

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Deep levels were observed using capacitance deep level optical spectroscopy (DLOS) in an AlGaN/GaN heterostructure equivalent to that of a heterojunction field effect transistor. Band gap states were assigned to either the AlGaN or GaN regions by comparing the DLOS spectra in accumulation and pinch-off modes, where the former reflects both AlGaN- and GaN-related defects, and the latter emphasizes defects residing in the GaN. A band gap state at Ec−3.85 eV was unambiguously identified with the AlGaN region, and deep levels at Ec−2.64 eV and Ec−3.30 eV were associated with the GaN layers. Both the AlGaN and GaN layers exhibited additional deep levels with large lattice relaxation. The influence of deep levels on the two-dimensional electron gas sheet charge was estimated using a lighted capacitance-voltage method.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.55.Eq III-V semiconductors
71.20.Nr Semiconductor compounds

Near-field scanning optical microscopy and time-resolved optical characterization of epitaxial lateral overgrown c-plane and a-plane GaN

Ü. Özgür, X. Ni, Y. Fu, H. Morkoç, and H. O. Everitt

Appl. Phys. Lett. 89, 262117 (2006); http://dx.doi.org/10.1063/1.2424677 (3 pages) | Cited 5 times

Online Publication Date: 29 December 2006

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Epitaxial lateral overgrowth (ELO) was employed for both c-plane and a-plane GaN layers on sapphire, and a more pronounced optical improvement was observed for the a-plane GaN as evidenced by the significantly increased band edge photoluminescence (PL). Room temperature near-field scanning optical microscopy studies explicitly showed enhanced optical quality in the wing regions of the overgrown GaN due to reduced density of dislocations, and for the a-plane ELO GaN sample the wings and the windows were clearly discernible from PL mapping. Time-resolved PL measurements revealed biexponential decays with time constants that were significantly enhanced for the a-plane ELO GaN (τ1 = 0.08 ns, τ2 = 0.25 ns) when compared to the non-ELO control sample but were still much shorter than those for the c-plane ELO GaN (τ1 = 0.26 ns, τ2 = 0.90 ns).
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78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.55.Cr III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

p-type conductivity and donor-acceptor pair emission in Cd1−xFexS dilute magnetic semiconductors

X. J. Wu, D. Z. Shen, Z. Z. Zhang, J. Y. Zhang, K. W. Liu, B. H. Li, Y. M. Lu, D. X. Zhao, and B. Yao

Appl. Phys. Lett. 89, 262118 (2006); http://dx.doi.org/10.1063/1.2425028 (3 pages) | Cited 5 times

Online Publication Date: 29 December 2006

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Cd1−xFexS thin films with different Fe contents were grown on c-plane sapphire by low-pressure metal organic chemical vapor deposition. The resistivity of the thin films was found to increase with the addition of more Fe contents into the Cd1−xFexS thin films by elevating the growth temperature, which was attributed to the ionization of holes from trivalent Fe ions. High density Fe doping eventually reversed the conductivity of Cd1−xFexS thin film from n to p type. With increasing Fe content, the band-to-band transition at 2.5 eV was suppressed while the emission from the donor-acceptor pairs at 2.0–2.4 eV finally dominated the photoluminescence spectra.
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81.05.Dz II-VI semiconductors
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
75.50.Pp Magnetic semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
78.55.Et II-VI semiconductors

Photocurrent and transmission spectroscopy of direct-gap interband transitions in Ge/SiGe quantum wells

S. Tsujino, H. Sigg, G. Mussler, D. Chrastina, and H. von Känel

Appl. Phys. Lett. 89, 262119 (2006); http://dx.doi.org/10.1063/1.2425032 (3 pages) | Cited 26 times

Online Publication Date: 29 December 2006

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The authors studied the direct-gap interband transitions in strain-compensated Ge/SiGe quantum wells grown by low energy plasma enhanced chemical vapor deposition. A series of excitonic interband absorptions from the quantized hole states to the quantized electronic states at the Γ7c− edge in the Ge wells is observed up to room temperature by photocurrent and transmission spectroscopy. The results are compared with theory. At low temperature, the quantum confined Stark effect is demonstrated in a Schottky diode geometry.
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78.66.Db Elemental semiconductors and insulators
73.63.Hs Quantum wells
78.67.De Quantum wells
72.40.+w Photoconduction and photovoltaic effects
73.21.Fg Quantum wells

Hysteresis mechanism in pentacene thin-film transistors with poly(4-vinyl phenol) gate insulator

Cheon An Lee, Dong-Wook Park, Keum-Dong Jung, Byung-ju Kim, Yoo Chul Kim, Jong Duk Lee, and Byung-Gook Park

Appl. Phys. Lett. 89, 262120 (2006); http://dx.doi.org/10.1063/1.2425042 (3 pages) | Cited 28 times

Online Publication Date: 29 December 2006

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The hysteresis mechanism is studied in pentacene organic thin-film transistors (OTFTs) with poly(4-vinyl phenol) (PVP) gate insulator by examining OTFTs with an oxide/PVP double layer gate insulator. The oxide thickness affects the direction of the hysteresis as well as its magnitude. This result can be explained on the basis of the charge injection and trapping mechanism rather than slow polarization or ion migration. The hysteresis occurs mainly due to the charges which could be injected from the gate electrode and trapped in the PVP. As the thickness of the oxide layer is increased, the gate charge injection is blocked and the effect of the charges from the channel increases.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Intrinsic crystalline-to-amorphous transition above 400 °C in plasma-deposited Si thin films

Toshihiro Kamei

Appl. Phys. Lett. 89, 262121 (2006); http://dx.doi.org/10.1063/1.2426905 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2006

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There has been long debate concerning why microcrystalline Si formation is disrupted at a deposition temperature above around 400 °C: is it due to the loss of surface hydrogen coverage or to the incorporation of oxygen impurities? The authors reduced the atmospheric concentration of such impurities as O, C, and N in this work by using an ultraclean plasma deposition apparatus and demonstrate that microcrystalline Si films showed improved crystallinity at a deposition temperature of 350 °C, resulting in a mobility of 5. As the deposition temperature was raised to 450 °C, however, the Raman spectrum shows an amorphous structure of the film under such clean conditions. According to secondary ion mass spectrometry, the O, C, and N concentrations in this film were as low as 1017, 1016, and 1017 cm−3, respectively, demonstrating that the crystalline-to-amorphous transition around 400 °C should be intrinsic under the present conditions and may be correlated with thermal hydrogen desorption on a film-growing surface.
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81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
68.55.A- Nucleation and growth
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
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