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27 Jul 1998

Volume 73, Issue 4, pp. 423-552

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Fracture phenomena in silicon imaged by infrared radiation from ejected small particles

E. Busch and D. Haneman

Appl. Phys. Lett. 73, 484 (1998); http://dx.doi.org/10.1063/1.121908 (3 pages) | Cited 2 times

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We have found that fracture of silicon wafer specimens without introduced flaws takes place with the ejection of many small particles that emit infrared radiation, which has been imaged with a sensitive CCD camera. The particles are of order micron dimensions, preventing surface-barrier separation of carriers excited by the bond breaking at cleavage. Furthermore, larger ejected particles can subsequently crack, allowing further ejection of small luminescent particles. The results show that a simple theory of spread of a pre-existing flaw can be a serious oversimplification of complex phenomena occurring at the onset of brittle cleavage. © 1998 American Institute of Physics.
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78.60.Mq Sonoluminescence, triboluminescence
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Adatom diffusion at GaN (0001) and (0001) surfaces

Tosja Zywietz, Jörg Neugebauer, and Matthias Scheffler

Appl. Phys. Lett. 73, 487 (1998); http://dx.doi.org/10.1063/1.121909 (3 pages) | Cited 170 times

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The diffusion of Ga and N adatoms has been studied for the technologically relevant wurtzite (0001) and (0001) surfaces employing density-functional theory. Our calculations reveal a very different diffusivity for Ga and N adatoms on the equilibrium surfaces: While Ga is very mobile at typical growth temperatures, the diffusion of N is by orders of magnitude slower. These results give a very detailed insight of how and under which growth conditions N adatoms can be stabilized and efficiently incorporated at the surface. We further find that the presence of excess N strongly increases the Ga diffusion barrier and discuss the consequences for the growth of GaN. © 1998 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Soft breakdown fluctuation events in ultrathin SiO2 layers

E. Miranda, J. Suñé, R. Rodríguez, M. Nafría, and X. Aymerich

Appl. Phys. Lett. 73, 490 (1998); http://dx.doi.org/10.1063/1.121910 (3 pages) | Cited 28 times

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When an ultrathin (<5 nm) oxide is subjected to electrical stress, several soft-breakdown events can occur prior to the final dielectric breakdown. After the occurrence of such failure events, the current–voltage (I–V) characteristic corresponds to the superposition of highly conductive spots and background conduction through the undegraded capacitor area. In this conduction regime, the application of a low constant voltage gives rise to large leakage current fluctuations in the form of random telegraph signal. Some of these fluctuations have been identified with ON/OFF switching events of one or more local conduction spots, and not with a modulation of their conductance. The experimental soft-breakdown I–V characteristics are shown to be better understood if the spot conduction is considered to be locally limited by the silicon electrodes and not by the oxide. © 1998 American Institute of Physics.
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73.61.Ng Insulators
77.22.Jp Dielectric breakdown and space-charge effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
73.50.Td Noise processes and phenomena

Role of localized and extended electronic states in InGaN/GaN quantum wells under high injection, inferred from near-field optical microscopy

A. Vertikov, A. V. Nurmikko, K. Doverspike, G. Bulman, and J. Edmond

Appl. Phys. Lett. 73, 493 (1998); http://dx.doi.org/10.1063/1.121911 (3 pages) | Cited 32 times

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We report on spatially resolved optical measurements of high-quality InGaN/GaN multiple quantum wells under conditions of direct high optical injection (>1019 cm−3) using near-field optical microscopy in the collection mode. The spectral dependence of the spatial distribution of the photoluminescence indicates that the range of In-composition fluctuations reaches the 100-nm lateral scale. The spectra are dependent on the carrier injection level and reveal significant state filling effect. We sketch tentative conclusions about the In-cluster size distribution in terms of contributions to the radiative processes that involve localized and extended states, respectively, in the regime of electron–hole (e–h) pair densities at which present diode lasers operate. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
73.20.Fz Weak or Anderson localization
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Effects of Si-doping in the barriers of InGaN multiquantum well purplish-blue laser diodes

S. Chichibu, D. A. Cohen, M. P. Mack, A. C. Abare, P. Kozodoy, M. Minsky, S. Fleischer, S. Keller, J. E. Bowers, U. K. Mishra, L. A. Coldren, D. R. Clarke, and S. P. DenBaars

Appl. Phys. Lett. 73, 496 (1998); http://dx.doi.org/10.1063/1.121912 (3 pages) | Cited 36 times

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Optical gain spectra of InGaN multiquantum well laser diode wafers having Si-doped or undoped InGaN barriers were compared. Although evidence for effective band-gap inhomogeneity was found in both structures, the wells with the Si-doped barriers exhibited a smaller Stokes-like shift. Si doping suppressed emergence of a secondary amplified spontaneous emission peak at 3.05 eV, which was uncoupled with the primary one at 2.93 eV. Furthermore Si doping reduced the threshold power density required to obtain the stimulated emission. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
61.72.uj III-V and II-VI semiconductors
78.45.+h Stimulated emission

Improved steady-state photocarrier grating in nanocrystalline thin films after surface-roughness reduction by mechanical polishing

R. Brüggemann

Appl. Phys. Lett. 73, 499 (1998); http://dx.doi.org/10.1063/1.121913 (3 pages) | Cited 2 times

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We detect elastic optical scattering resulting from the surface roughness of nanocrystalline silicon by a poor optical grating in the steady-state photocarrier grating experiment. The small variation of the experimental sampling function reduces the reliability of the ambipolar diffusion length measurements in this case. We demonstrate that the reduction in surface roughness of nanocrystalline silicon by polishing reduces optical scattering, improves the grating quality, and allows a reliable determination of the ambipolar diffusion length, making the experiment attractive for characterizing nanocrystalline silicon and other semiconductors which exhibit optical scattering. © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.65.Ps Polishing, grinding, surface finishing
42.79.Dj Gratings
73.50.Pz Photoconduction and photovoltaic effects
72.40.+w Photoconduction and photovoltaic effects
81.07.-b Nanoscale materials and structures: fabrication and characterization
68.35.B- Structure of clean surfaces (and surface reconstruction)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Cw Elemental semiconductors
78.66.Db Elemental semiconductors and insulators

Air-gap amorphous silicon thin film transistors

M. Boucinha, V. Chu, and J. P. Conde

Appl. Phys. Lett. 73, 502 (1998); http://dx.doi.org/10.1063/1.121914 (3 pages) | Cited 11 times

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Top gate and bottom gate amorphous silicon thin film transistors where the dielectric has been replaced by an air gap have been fabricated on glass substrates using surface micromachining techniques. Bridges were formed by using low density silicon nitride as a sacrificial layer. In bottom gate structures the bridge material was amorphous silicon and in top gate structures it was highly doped n+ microcrystalline silicon. The first working devices show transistor behavior with field effect mobilities between 0.1 and 0.5 cm2 V−1 s−1. © 1998 American Institute of Physics.
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85.30.Tv Field effect devices
73.61.Jc Amorphous semiconductors; glasses

Selective formation and alignment of InAs quantum dots over mesa stripes along the [011] and [001] directions on GaAs (100) substrates

R. Zhang, R. Tsui, K. Shiralagi, D. Convey, and H. Goronkin

Appl. Phys. Lett. 73, 505 (1998); http://dx.doi.org/10.1063/1.121915 (3 pages) | Cited 18 times

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We have studied the selective formation of InAs self-organized quantum dots on top of [001]- and [011]-oriented mesa stripes on patterned GaAs (100) substrates. The GaAs stripes are also grown by selective area epitaxy. The dot density and spatial distribution depend on both the stripe orientation and the width of the (100) top facet of the stripe. The density is higher for stripes aligned in the [001] direction, and lower for those aligned in the [011] direction, respectively, when compared to that obtained on a planar substrate under the same growth conditions. In addition, the dot uniformity is improved by reducing the top facet width below 200 nm in the growth of the mesa stripes, and well-aligned rows of dots are obtained for sub-100-nm widths. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors

Vacancy defects in thin-film La0.5Sr0.5CoO3−δ observed by positron annihilation

D. J. Keeble, A. Krishnan, T. Friessnegg, B. Nielsen, S. Madhukar, S. Aggarwal, R. Ramesh, and E. H. Poindexter

Appl. Phys. Lett. 73, 508 (1998); http://dx.doi.org/10.1063/1.121916 (3 pages) | Cited 14 times

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Vacancy-related defects in laser ablated thin films of the conducting metal–oxide La0.5Sr0.5CoO3−δ were detected using a variable-energy positron beam. The nonstoichiometry, δ, was altered by varying the oxygen partial pressure within the deposition chamber present during cooling. Conductivity measurements confirmed the change in oxygen content. Increased positron trapping at vacancy defects was observed with increasing nonstoichiometry. It is proposed that vacancy clusters were present in the film cooled in 10−5 Torr oxygen. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.66.Bi Elemental solids
61.66.Dk Alloys
61.72.J- Point defects and defect clusters
78.70.Bj Positron annihilation
81.15.Fg Pulsed laser ablation deposition

Stimulated emission in ridge quantum wire laser structures measured with optical pumping and microscopic imaging methods

Shinichi Watanabe, Shyun Koshiba, Masahiro Yoshita, Hiroyuki Sakaki, Motoyoshi Baba, and Hidefumi Akiyama

Appl. Phys. Lett. 73, 511 (1998); http://dx.doi.org/10.1063/1.121917 (3 pages) | Cited 5 times

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We report the observation of stimulated emission in ridge quantum wire (QWR) structures at temperatures from 4.7 to 290 K. To examine the origin of the stimulated emission, the spatially and spectrally resolved microscopic images of the emission were measured. It was most likely attributed to the optical transition between the excited states in QWRs. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission
78.66.Fd III-V semiconductors

Soft breakdown in ultrathin gate oxides: Correlation with the percolation theory of nonlinear conductors

M. Houssa, T. Nigam, P. W. Mertens, and M. M. Heyns

Appl. Phys. Lett. 73, 514 (1998); http://dx.doi.org/10.1063/1.121918 (3 pages) | Cited 46 times

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The dielectric breakdown under constant current stressing of 4.2 nm SiO2 gate oxides is investigated. After soft breakdown, which corresponds to an anomalous increase of the stress-induced leakage current of metal–oxide–semiconductor capacitors, the current behaves like a power law of the applied gate voltage VG. After soft breakdown, charge is further injected into the SiO2 layer in order to extract the effective resistivity ρeff of the system as a function of the density of oxide traps D generated in the layer. It is found that ρeff behaves like a power law of (D−Dc) where Dc is the critical density of traps generated at soft breakdown. These results are in fair agreement with the predictions of the percolation theory of nonlinear conductor networks. Besides, the value of the critical exponent related to the resistivity is close to the one expected in two dimensions. © 1998 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.22.Jp Dielectric breakdown and space-charge effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.61.Ng Insulators

Near-field magneto-optical spectroscopy of single self-assembled InAs quantum dots

Y. Toda, S. Shinomori, K. Suzuki, and Y. Arakawa

Appl. Phys. Lett. 73, 517 (1998); http://dx.doi.org/10.1063/1.121919 (3 pages) | Cited 35 times

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We report observations of Zeeman spin splitting in photoluminescence from single InAs/GaAs self-assembled quantum dots (SAQDs) fabricated by Stranski–Krastanow growth. A low-temperature near-field optical microscope incorporating a superconducting magnet enabled us to resolve the luminescence from individual SAQDs. We have measured Zeeman split components from single SAQDs in magnetic fields up to 10 T. Circularly-polarized photoluminescence resolved carriers of different spin polarity. Dependence of the splitting on the QD structures was also investigated. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.20.Ls Magneto-optical effects
73.61.Ey III-V semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Electroluminescence efficiency of 1.3 μm wavelength InGaAs/GaAs quantum dots

D. L. Huffaker and D. G. Deppe

Appl. Phys. Lett. 73, 520 (1998); http://dx.doi.org/10.1063/1.121920 (3 pages) | Cited 82 times

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Data are presented characterizing the spectral emission and the electroluminescence efficiency dependence on growth conditions of 1.3 μm wavelength InGaAs/GaAs quantum dots. We show that highly efficient 1.3 μm room temperature electroluminescence can be achieved with only ten total deposited monolayers with an averaged In content of 50%. Atomic force microscopy shows that the 1.3 μm wavelength quantum dots form with a density of ∼ 1.3×1010 cm−2. © 1998 American Institute of Physics.
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78.60.Fi Electroluminescence
78.66.Fd III-V semiconductors
68.35.Ct Interface structure and roughness
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Luminescence efficiency measurements of silicon nanoclusters

A. J. Kenyon, P. F. Trwoga, C. W. Pitt, and G. Rehm

Appl. Phys. Lett. 73, 523 (1998); http://dx.doi.org/10.1063/1.121921 (3 pages) | Cited 18 times

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We present the results of what we believe to be the first study of the power efficiency of room temperature photoluminescence from thin films of silica containing silicon nanoclusters. Films were prepared by plasma enhanced chemical vapor deposition from silane and nitrous oxide precursors. Luminescence was excited using the 476 nm line of an argon-ion laser. We have measured power efficiencies for samples that exhibit luminescence solely due to radiative recombination of quantum confined excitons. Efficiencies around 0.04% are reported. © 1998 American Institute of Physics.
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78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
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.)
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.66.Db Elemental semiconductors and insulators
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Long-wavelength lasing from InAs self-assembled quantum dots on (311) B InP

Kenichi Nishi, Mitsuki Yamada, Takayoshi Anan, Akiko Gomyo, and Shigeo Sugou

Appl. Phys. Lett. 73, 526 (1998); http://dx.doi.org/10.1063/1.121922 (3 pages) | Cited 21 times

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Nanometer-scale InAs quantum dots were grown on InP by self-assembly using gas-source molecular beam epitaxy. InAs depositions of 0.33 nm in nominal thickness were found to form quantum dots on (311) B InP with a lateral dimension of about 43 nm and a density of 2×1010 cm−2. A laser structure with seven periods of the quantum dot active layers lased in a wavelength range from 1.1 to 1.4 μm at 77 K under pulsed current injection. The lasing wavelength changed to a shorter wavelength as the cavity length decreased, indicating gain saturation due to state filling effect in discrete quantum levels, which is typical in quantum dot lasers. This phenomenon can be used to achieve wide-range multiwavelength lasers for optical communication, that can be adjusted merely by changing the effective cavity length. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization

Carbon nanotube tipped atomic force microscopy for measurement of <100 nm etch morphology on semiconductors

G. Nagy, M. Levy, R. Scarmozzino, R. M. Osgood, H. Dai, R. E. Smalley, C. A. Michaels, G. W. Flynn, and G. F. McLane

Appl. Phys. Lett. 73, 529 (1998); http://dx.doi.org/10.1063/1.122069 (3 pages) | Cited 41 times

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The use of carbon nanotubes as tips in atomic force microscopy for a systematic study of dry etching pattern transfer in GaAs is described. The GaAs samples are patterned via electron beam lithography and then etched using magnetron reactive ion or chemically assisted ion beam processing. The technique allows diagnosis, in air, of etched features with scale sizes of <100 nm. ©1998 American Institute of Physics.
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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
81.05.Ea III-V semiconductors
85.40.Hp Lithography, masks and pattern transfer
61.46.-w Structure of nanoscale materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning

Impact excitation of the f–f emission in clusters Er–O in silicon

L. G. Gerchikov and V. F. Masterov

Appl. Phys. Lett. 73, 532 (1998); http://dx.doi.org/10.1063/1.121923 (3 pages) | Cited 4 times

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The Er2O3 quantum dot (cluster) with dimensions about 1.2 nm in silicon is discussed as a possible source of the Er-related emission in Si:Er, O, excited by hot carriers in the light-emitting diodes under reverse bias. This quantum dot is represented as a spherical quantum well 1 eV in depth. The electron resonance level with energy about 0.8 eV above the bottom of the silicon conduction band plays the role of an electron trap. The energy of 1.6 eV hot electrons trapped by the Er–O cluster is transferred to excitation of the f shell of erbium. © 1998 American Institute of Physics.
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71.55.Cn Elemental semiconductors
72.20.Ht High-field and nonlinear effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.40.Fy Semiconductors
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