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6 Dec 1999

Volume 75, Issue 23, pp. 3593-3720

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Relationship between sp2 carbon content and E04 optical gap in amorphous carbon-based materials

C. Oppedisano and A. Tagliaferro

Appl. Phys. Lett. 75, 3650 (1999); http://dx.doi.org/10.1063/1.125417 (3 pages) | Cited 28 times

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A decreasing trend of the optical gap E04 with increasing sp2 carbon content has been noticed in amorphous carbon thin films. This behavior is common to materials grown using different deposition methods and having different composition and local structure. The use of a model of density of states in which the π bands are assumed to be Gaussian shaped allows us to explain such behavior, once the role of network distortion and hydrogen content in determining the width of the bands is taken into account. © 1999 American Institute of Physics.
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71.23.Cq Amorphous semiconductors, metallic glasses, glasses
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.20.At Surface states, band structure, electron density of states
61.43.-j Disordered solids
78.66.Nk Insulators

High-frequency AlGaN/GaN polarization-induced high electron mobility transistors grown by plasma-assisted molecular-beam epitaxy

M. J. Murphy, K. Chu, H. Wu, W. Yeo, W. J. Schaff, O. Ambacher, L. F. Eastman, T. J. Eustis, J. Silcox, R. Dimitrov, and M. Stutzmann

Appl. Phys. Lett. 75, 3653 (1999); http://dx.doi.org/10.1063/1.125418 (3 pages) | Cited 28 times

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High-quality AlGaN/GaN heterostructures have been grown on sapphire substrates by plasma-assisted molecular-beam epitaxy. Polarization effects are exploited to achieve a two-dimensional electron-gas sheet density of 8.8×1012 cm−2 and greater on intentionally undoped material with a measured room-temperature mobility as high as 1478 cm2/V s. Transistors were then fabricated from this material, yielding a unity current gain frequency of 50 GHz and a unity power gain frequency of 97 GHz. By increasing the buffer layer thickness, output powers of 1.88 W/mm at 4 GHz with an efficiency of 34% were achieved. These results prove that the polarization effects in the nitrides are as enormous as theory predicts. The key to the improved mobility and operation of the devices of the all-molecular-beam-epitaxy-grown material, the AlN nucleation layer, will be discussed. © 1999 American Institute of Physics.  
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85.30.Tv Field effect devices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
73.61.Ey III-V semiconductors

Spectrally resolved luminescence from an InGaAs quantum well induced by an ambient scanning tunneling microscope

M. Kemerink, J. W. Gerritsen, P. M. Koenraad, H. van Kempen, and J. H. Wolter

Appl. Phys. Lett. 75, 3656 (1999); http://dx.doi.org/10.1063/1.125419 (3 pages) | Cited 9 times

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Spectrally resolved scanning tunneling microscope-induced luminescence has been obtained under ambient conditions, i.e., at room temperature, in air, by passivating the sample surface with sulfur. This passivation turned out to be essential to suppress the local anodic oxidation induced by the tunneling current. From the dependence of the luminescence signal on tunneling current and voltage, we find that the passivation solution and post-passivation annealing temperature strongly modify the surface density of states (SDOS). More specifically, we found evidence that, after annealing at 400 °C, no SDOS is left above the bottom of the conduction band. For annealing at 200 °C, the SDOS is found to be extended up to 1.0±0.2 eV above the bottom of the conduction band. In all cases, the passivated (001) surface appears to be completely pinned. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
78.60.Fi Electroluminescence
61.72.Cc Kinetics of defect formation and annealing
81.65.Rv Passivation

Transient enhanced diffusion after laser thermal processing of ion implanted silicon

Kevin S. Jones, Heather Banisaukas, Josh Glassberg, Ebrahim Andideh, Craig Jasper, Allen Hoover, Aditya Agarwal, and Mike Rendon

Appl. Phys. Lett. 75, 3659 (1999); http://dx.doi.org/10.1063/1.125420 (3 pages) | Cited 13 times

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The effect of laser thermal processing (LTP) on implantation-induced defect evolution and transient enhanced diffusion (TED) of boron was investigated. A 270-Å-thick amorphous layer formed by 10 keV Si+ implantation was melted and regrown using a 20 ns ultraviolet laser pulse. Transmission electron microscopy revealed that recrystallization of the amorphous layer following LTP results in a high concentration of stacking faults and microtwins in the regrown region. Also, the end-of-range loop evolution during subsequent 750 °C furnace annealing, is different in a LTP sample compared to a control sample. Secondary ion mass spectroscopy of a boron marker layer 6000 Å below the surface showed that LTP alone produced no enhanced diffusion. However, during subsequent furnace annealing, the boron layer in the LTP sample experienced just as much TED as in the control sample which was only implanted and furnace annealed. These results imply that laser melting and recrystallization of an implantation-induced amorphous layer does not measurably reduce the excess interstitials released from the end-of-range implant damage. © 1999 American Institute of Physics.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
66.30.J- Diffusion of impurities
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
61.72.Nn Stacking faults and other planar or extended defects
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.05.Cy Elemental semiconductors
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Cyclotron resonance in modulation-doped ZnSe/Zn1−xCdxSe and ZnTe/CdSe single quantum wells

H. K. Ng, Y. A. Leem, R. Knobel, I. P. Smorchkova, A. A. Sirenko, and N. Samarth

Appl. Phys. Lett. 75, 3662 (1999); http://dx.doi.org/10.1063/1.125421 (3 pages) | Cited 6 times

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We report low-temperature (4.2 K) cyclotron resonance measurements on high-mobility, two-dimensional electron gases in modulation-doped ZnSe/Zn1−xCdxSe (x = 0.06, 0.12, and 0.24) single quantum wells, as well as in a modulation-doped ZnTe/CdSe single quantum well. These experiments carried out in magnetic fields ranging up to 17 T yield reliable measurements of the effective mass m∗ of conduction-band electrons in Zn1−xCdxSe alloys, including the measurement of m∗ in cubic CdSe. © 1999 American Institute of Physics.
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76.40.+b Diamagnetic and cyclotron resonances
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Subpicosecond spin relaxation in GaAsSb multiple quantum wells

K. C. Hall, S. W. Leonard, H. M. van Driel, A. R. Kost, E. Selvig, and D. H. Chow

Appl. Phys. Lett. 75, 3665 (1999); http://dx.doi.org/10.1063/1.125422 (3 pages) | Cited 14 times

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Spin relaxation times in GaAsxSb1−x quantum wells are measured at 295 K using time-resolved circular dichroism induced by 1.5 μm, 100 fs pulses. Values of 1.03 and 0.84 ps are obtained for samples with x = 0 and 0.188, respectively. These times are >5 times shorter than those in InGaAs and InGaAsP wells with similar band gaps. The shorter relaxation times are attributed to the larger spin-orbit conduction-band splitting in the Ga(As)Sb system, consistent with the D’yakonov–Perel theory of spin relaxation [M. I. D’yakonov and V. I. Perel, Sov. Phys. JETP 38, 177 (1974)]. Our results indicate the feasibility of engineering an all-optical, polarization switch at 1.5 μm with response time <250 fs. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.20.Fm Birefringence
78.47.-p Spectroscopy of solid state dynamics
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Erasable nanometer-scale modification at the Au/Si interface by ballistic electron emission microscopy

Y. Hasegawa, K. Akiyama, M. Ono, S.-J. Kahng, Q. K. Xue, K. Nakayama, T. Hashizume, and T. Sakurai

Appl. Phys. Lett. 75, 3668 (1999); http://dx.doi.org/10.1063/1.125423 (3 pages) | Cited 3 times

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We report that local modification and its erasing with a nanometer-scale size can be performed at a Au/Si(111) interface using ballistic electron emission microscopy (BEEM). By applying a negative voltage on the tip, a region was created where no BEEM current flows at the interface and was imaged with BEEM. The modified area can be erased by applying a voltage with the opposite polarity. It is found that the minimum size of writing and erasing corresponds to Au grains, suggesting a method of rewritable memory on a nanometer-scale dimension. © 1999 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
68.37.Vj Field emission and field-ion microscopy
73.40.Ns Metal-nonmetal contacts
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Activation energy for fluorine transport in amorphous silicon

G. R. Nash, J. F. W. Schiz, C. D. Marsh, P. Ashburn, and G. R. Booker

Appl. Phys. Lett. 75, 3671 (1999); http://dx.doi.org/10.1063/1.125424 (3 pages) | Cited 13 times

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The transport of ion-implanted F in amorphous Si is studied using secondary ion mass spectroscopy and transmission electron microscopy. Significant redistribution of F is observed at temperatures in the range 600–700 °C. The measured F depth profiles are modeled using a simple Gaussian solution to the diffusion equation, and the diffusion coefficient is deduced at each temperature. An activation energy of 2.2 eV±0.4 eV for F transport is extracted from an Arrhenius plot of the diffusion coefficients. It is shown that the F transport is influenced by implantation-induced defects. © 1999 American Institute of Physics.
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66.30.J- Diffusion of impurities
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys

High energy-barrier for defect creation in thin-film transistors based on hot-wire amorphous silicon

B. Stannowski, R. E. I. Schropp, and A. Nascetti

Appl. Phys. Lett. 75, 3674 (1999); http://dx.doi.org/10.1063/1.125425 (3 pages) | Cited 4 times

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Thin-film transistors based on amorphous silicon deposited by hot-wire chemical-vapor deposition (CVD) exhibited a high mean barrier height of 1.074 eV for defect creation after gate-voltage stress. This is 77 meV higher than for glow-discharge devices. Transistors with a SiO2 or a-SiNx:H gate dielectric showed good performance with a field-effect mobility up to 0.7 cm2/V s. Thus, good thin-film transistors with a superior stability can be deposited by hot-wire CVD at high deposition rates of 1.7 nm/s. We demonstrate that a reduced defect creation in the silicon and not the hot-wire-specific absence of interface ion bombardment is responsible for this higher stability. © 1999 American Institute of Physics.
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85.30.Tv Field effect devices
61.43.Dq Amorphous semiconductors, metals, and alloys
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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