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17 Jan 2000

Volume 76, Issue 3, pp. 253-392

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Polarity-dependent rejuvenation of ferroelectric properties of integrated SrBi2Ta2O9 capacitors by electrical stressing

Suk-Kyoung Hong, Cheol Seong Hwang, Oh Seong Kwon, and Nam Soo Kang

Appl. Phys. Lett. 76, 324 (2000); http://dx.doi.org/10.1063/1.125764 (3 pages) | Cited 12 times

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The electric-field-induced rejuvenation behavior of the degraded ferroelectric properties of integrated Pt/SrBi2Ti2O9/Pt capacitors was investigated. Integration processes, especially plasma-enhanced chemical vapor deposition of the passivation layers, generate hydrogen ions and electrons which act as domain pinning centers and a source of a negative internal electric field. Domain pinning was found to reduce the remanent polarization (Pr) and internal field that induces an imprint to the positive bias direction. Alternating current cyclings with peak voltages of +/−6 V rejuvenated the degraded ferroelectric performance of the capacitors. Cycling with a negative bias was more effective in fixing the damage than was a positive bias. Baking at 125 °C again degraded the rejuvenated ferroelectric performance. The degree of re-degradation was also dependent on the polarity of the rejuvenating bias. The polarity-dependent behavior of rejuvenation was explained on the basis of a negative-internal-field model due to preferential capture of electrons from the plasma at the top electrodes. © 2000 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
77.22.Ej Polarization and depolarization
84.30.Sk Pulse and digital circuits

Metal-sulfur-based air-stable passivation of GaAs with very low surface-state densities

Carol I. H. Ashby, Kevin R. Zavadil, Albert G. Baca, P.-C. Chang, B. E. Hammons, and M. J. Hafich

Appl. Phys. Lett. 76, 327 (2000); http://dx.doi.org/10.1063/1.125734 (3 pages) | Cited 7 times

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An air-stable electronic surface passivation for GaAs and other III–V compound semiconductors that employs sulfur and a suitable metal ion, e.g., Zn, and that is robust towards plasma dielectric deposition has been developed. Initial improvements in photoluminescence are twice that of S-only treatments and have been preserved for >11 months with SiOxNy dielectric encapsulation. Photoluminescence and x-ray photoelectron spectroscopies indicate that the passivation consists of two major components with one being stable for >2 years in air. This process improves heterojunction bipolar transistor current gain for both large and small area devices. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.65.Rv Passivation
73.20.At Surface states, band structure, electron density of states
78.55.Cr III-V semiconductors
79.60.Dp Adsorbed layers and thin films
85.30.Pq Bipolar transistors

Six-bilayer periodic structures in GaN grown on GaAs(001)

Mitsuru Funato, Teruki Ishido, Shizuo Fujita, and Shigeo Fujita

Appl. Phys. Lett. 76, 330 (2000); http://dx.doi.org/10.1063/1.125735 (3 pages) | Cited 2 times

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We have observed six-bilayer periodic structures in GaN grown on GaAs(001). The periodicity occurs along the zinc-blende(ZB)-[111]A direction, suggesting that it originates from stacking faults on close-packed planes. GaN grown on GaAs includes both ZB and wurtzite phases as a result of formation of stacking faults and the periodic structures are mostly located between these two crystalline phases. Based on this observation, possible layer stacking sequences are proposed, which are classified as 6H polytypes. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Nn Stacking faults and other planar or extended defects
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Piezoelectric field-enhanced second-order nonlinear optical susceptibilities in wurtzite GaN/AlGaN quantum wells

Ansheng Liu, S.-L. Chuang, and C. Z. Ning

Appl. Phys. Lett. 76, 333 (2000); http://dx.doi.org/10.1063/1.125736 (3 pages) | Cited 26 times

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Second-order nonlinear optical processes including second-harmonic generation, optical rectification, and difference-frequency generation associated with intersubband transitions in wurtzite GaN/AlGaN quantum well (QW) are investigated theoretically. Taking into account the strain-induced piezoelectric (PZ) effects, we solve the electronic structure of the QW from coupled effective-mass Schrödinger equation and Poisson equation including the exchange-correlation effect under the local-density approximation. We show that the large PZ field in the QW breaks the symmetry of the confinement potential profile and leads to large second-order susceptibilities. We also show that the interband optical pump-induced electron-hole plasma results in an enhancement in the maximum value of the nonlinear coefficients and a redshift of the peak position in the nonlinear optical spectrum. By use of the difference-frequency generation, THz radiation can be generated from a GaN/Al0.75Ga0.25N with a pump laser of 1.55 μm. © 2000 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Fd III-V semiconductors
77.65.Ly Strain-induced piezoelectric fields
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Shallow electron traps at the 4H–SiC/SiO2 interface

V. V. Afanas’ev, A. Stesmans, M. Bassler, G. Pensl, and M. J. Schulz

Appl. Phys. Lett. 76, 336 (2000); http://dx.doi.org/10.1063/1.125737 (3 pages) | Cited 34 times

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Low-temperature electrical measurements and photon-stimulated electron tunneling experiments reveal the presence of a high density of interface states at around 0.1 eV below the conduction band of 4H–SiC at its interface with thermally grown SiO2. These states, related to defects in the near-interfacial oxide layer, trap a considerable density of electrons from the SiC, and are likely responsible for the severe degradation of the electron mobility observed in the surface channel of 4H–SiC/SiO2 devices. The negative impact of the observed defects can be minimized by using SiC modifications (e.g., 6H, 15R, 3C) with a larger conduction band offset with the oxide than 4H–SiC leading to a largely reduced density of electrons trapped in the oxide. © 2000 American Institute of Physics.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.55.Ht Other nonmetals
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.40.Gk Tunneling

Comparison of the k⋅p and direct diagonalization approaches to the electronic structure of InAs/GaAs quantum dots

L. W. Wang, A. J. Williamson, Alex Zunger, H. Jiang, and J. Singh

Appl. Phys. Lett. 76, 339 (2000); http://dx.doi.org/10.1063/1.125747 (3 pages) | Cited 67 times

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We present a comparison of the 8-band k⋅p and empirical pseudopotential approaches to describing the electronic structure of pyramidal InAs/GaAs self-assembled quantum dots. We find a generally good agreement between the two methods. The most significant differences found in the k⋅p calculation are (i) a reduced splitting of the electron p states (3 vs 24 meV), (ii) an incorrect in-plane polarization ratio for electron-hole dipole transitions (0.97 vs 1.24), and (iii) an over confinement of both electron (48 meV) and hole states (52 meV), resulting in a band gap error of 100 meV. We introduce a “linear combination of bulk bands” technique which produces results similar to a full direct diagonalization pseudopotential calculation, at a cost similar to the k⋅p method. © 2000 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.05.Ea III-V semiconductors
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
71.20.Nr Semiconductor compounds

Contribution of radicals and ions in atomic-order plasma nitridation of Si

Takuya Seino, Takashi Matsuura, and Junichi Murota

Appl. Phys. Lett. 76, 342 (2000); http://dx.doi.org/10.1063/1.125748 (3 pages) | Cited 7 times

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Atomic-order nitridation of Si(100) by an ultraclean electron-cyclotron-resonance nitrogen plasma and contribution of radicals and ions to the nitridation have been investigated. The N atom concentration on Si(100) increases with the plasma exposure time and tends to saturate to a value corresponding to a few atomic layers. In the initial stage, the N atom concentration is normalized by the product of the relative radical density with the nitrogen plasma exposure time and the number of the incident ions is much smaller than the nitridation amount, which means the radical reaction is dominant. Assuming Langmuir-type kinetics neglecting desorption, an excellent agreement is observed by fitting the experimental data. In the saturation region, the N atom concentration is normalized by the number of incident ions and becomes higher than that corresponding to the double atomic layers. Therefore, it is suggested that nitridation of the deeper atoms below the surface is induced by the ion incidence. © 2000 American Institute of Physics.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Highly sensitive ultraviolet photodetectors based on Mg-doped hydrogenated GaN films grown at 380 °C

Shigeru Yagi

Appl. Phys. Lett. 76, 345 (2000); http://dx.doi.org/10.1063/1.125749 (3 pages) | Cited 16 times

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Excellent photoelectrical properties are reported for Mg-doped hydrogenated GaN (GaN:H) films grown at 380 °C. These films are fabricated using dual remote-plasma metalorganic chemical vapor deposition under hydrogen-rich conditions. Infrared spectra exhibit N–H and Ga–H vibration bands but not a Mg–H band. The spectral photoresponse of Al/Mg-doped GaN:H/Au sandwich-type cells reveals that the peak responsivity is 0.11 A/W at 360 nm with the dark current of 10−11 A at −1 V bias. The application in low-cost high-sensitivity visible blind ultraviolet sensors are exhibited for the films. © 2000 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Pw Imaging detectors and sensors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.50.Pz Photoconduction and photovoltaic effects

Top-gating of p-Si/SiGe/Si inverted modulation-doped structures

M. A. Sadeghzadeh

Appl. Phys. Lett. 76, 348 (2000); http://dx.doi.org/10.1063/1.125750 (3 pages) | Cited 2 times

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Low-temperature electrical properties of two-dimensional hole gases (2-DHGs) in Si/Si0.8Ge0.2/Si inverted modulation-doped structures have been investigated at different hole densities using a metal semiconductor gate sputtered on top of these structures. The 2-DHG which is supplied to the inverted interface of Si/SiGe/Si quantum well by a Si boron-doped layer spatially grown beneath the alloy, was controlled in the range of 1.5–7.8×1011 cm−2 hole density by biasing the top gate. With increasing 2-DHG sheet density, the hole wave function of these structures expands and moves away from inverted interface, consequently the mobility enhances. These results may be understood theoretically by elaborating the role of interface charge, roughness, and alloy scattering mechanisms in limiting the mobility of holes at the inverted interface. © 2000 American Institute of Physics.
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73.61.Cw Elemental semiconductors
73.61.Le Other inorganic semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Dn Low-field transport and mobility; piezoresistance
73.25.+i Surface conductivity and carrier phenomena
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Size-dependent electron-hole exchange interaction in Si nanocrystals

M. L. Brongersma, P. G. Kik, A. Polman, K. S. Min, and Harry A. Atwater

Appl. Phys. Lett. 76, 351 (2000); http://dx.doi.org/10.1063/1.125751 (3 pages) | Cited 98 times

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Silicon nanocrystals with diameters ranging from ≈2 to 5.5 nm were formed by Si ion implantation into SiO2 followed by annealing. After passivation with deuterium, the photoluminescence (PL) spectrum at 12 K peaks at 1.60 eV and has a full width at half maximum of 0.28 eV. The emission is attributed to the recombination of quantum-confined excitons in the nanocrystals. The temperature dependence of the PL intensity and decay rate at several energies between 1.4 and 1.9 eV was determined between 12 and 300 K. The temperature dependence of the radiative decay rate was determined, and is in good agreement with a model that takes into account the energy splitting between the excitonic singlet and triplet levels due to the electron-hole exchange interaction. The exchange energy splitting increases from 8.4 meV for large nanocrystals (≈5.5 nm) to 16.5 meV for small nanocrystals (≈2 nm). For all nanocrystal sizes, the radiative rate from the singlet state is 300–800 times larger than the radiative rate from the triplet state. © 2000 American Institute of Physics.
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71.70.Gm Exchange interactions
71.35.Gg Exciton-mediated interactions
78.55.Ap Elemental semiconductors
78.66.Vs Fine-particle systems
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.66.Db Elemental semiconductors and insulators
61.72.uf Ge and Si
61.72.Cc Kinetics of defect formation and annealing
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