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16 Aug 1999

Volume 75, Issue 7, pp. 885-1026

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Semi-insulating C-doped GaN and high-mobility AlGaN/GaN heterostructures grown by ammonia molecular beam epitaxy

J. B. Webb, H. Tang, S. Rolfe, and J. A. Bardwell

Appl. Phys. Lett. 75, 953 (1999); http://dx.doi.org/10.1063/1.124252 (3 pages) | Cited 58 times

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A method of growing semi-insulating GaN epilayers by ammonia molecular beam epitaxy through intentional doping with carbon is reported. Thick GaN layers of high resistivity are an important element in GaN-based heterostructure field-effect transistors. A methane ion source was used as the carbon dopant source. The cracking of the methane gas by the ion source was found to be the key to the effective incorporation of carbon. High-quality C-doped GaN layers with resistivities greater than 106 Ω cm have been grown with high reproducibility and reliability. AlGaN/GaN heterostructures grown on the C-doped semi-insulating GaN-based layers exhibited a high-mobility two-dimensional electron gas at the heterointerface, with room-temperature mobilities typically between 1000 and 1200 cm2/V s, and liquid-nitrogen-temperature mobilities up to 5660 cm2/V s. The carrier density was almost constant, with less than 3% change over the measured temperature range. © 1999 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.30.Tv Field effect devices
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.uj III-V and II-VI semiconductors

Buried single CdTe/CdMnTe quantum dots realized by focused ion beam lithography

G. Bacher, T. Kümmell, D. Eisert, A. Forchel, B. König, W. Ossau, C. R. Becker, and G. Landwehr

Appl. Phys. Lett. 75, 956 (1999); http://dx.doi.org/10.1063/1.124565 (3 pages) | Cited 18 times

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Buried single CdTe/CdMnTe quantum dots are realized by implantation-induced intermixing using a focused 100 keV Ga+ ion beam. For an implantation dose of 5×1013 cm−2 and an annealing temperature of 390 °C, a lateral potential depth of about 65 meV is obtained. By means of photoluminescence spectroscopy, the formation of zero-dimensional multiexcitons in single quantum dots is investigated, yielding a biexciton binding energy of about 3.5 meV. In addition, the occurrence of an excited biexciton transition in the photoluminescence spectrum gives clear evidence of a suppressed exciton spin-flip process in quantum dots. © 1999 American Institute of Physics.
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81.05.Dz II-VI semiconductors
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Modeling the breakdown spots in silicon dioxide films as point contacts

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

Appl. Phys. Lett. 75, 959 (1999); http://dx.doi.org/10.1063/1.124566 (3 pages) | Cited 12 times

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Experiments and simulations are combined to demonstrate that the hard dielectric breakdown of thin SiO2 films in polycrystaline silicon/oxide/semiconductor structures leads to the formation of conduction paths with atomic-size dimensions which behave as point contacts between the silicon electrodes. Depending on the area of the breakdown spots, the conduction properties of the breakdown paths are shown to be those of a classical Sharvin point contact or of a quantum point contact. © 1999 American Institute of Physics.
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77.22.Jp Dielectric breakdown and space-charge effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Hi Surface barrier, boundary, and point contact devices
73.23.-b Electronic transport in mesoscopic systems
85.35.Ds Quantum interference devices

From visible to white light emission by GaN quantum dots on Si(111) substrate

B. Damilano, N. Grandjean, F. Semond, J. Massies, and M. Leroux

Appl. Phys. Lett. 75, 962 (1999); http://dx.doi.org/10.1063/1.124567 (3 pages) | Cited 134 times

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GaN quantum dots (QDs) in an AlN matrix have been grown on Si(111) by molecular-beam epitaxy. The growth of GaN deposited at 800 °C on AlN has been investigated in situ by reflection high-energy electron diffraction. It is found that a growth interruption performed at GaN thicknesses larger than three molecular monolayers (8 Å) instantaneously leads to the formation of three-dimensional islands. This is used to grow GaN/AlN QDs on Si(111). Depending on their sizes, intense room-temperature photoluminescence is observed from blue to orange. Finally, we demonstrate that stacking of QD planes with properly chosen dot sizes gives rise to white light emission. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Nonlinear acoustoelectric interactions in GaAs/LiNbO3 structures

M. Rotter, A. Wixforth, A. O. Govorov, W. Ruile, D. Bernklau, and H. Riechert

Appl. Phys. Lett. 75, 965 (1999); http://dx.doi.org/10.1063/1.124568 (3 pages) | Cited 7 times

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Surface acoustic waves accompanied by very large piezoelectric fields can be created in a semiconductor/piezoelectric hybrid system. Such intense waves interact with the mobile carries in semiconductor quantum well structures in a manner being strongly governed by nonlinear effects. At high sound intensities, a formerly homogeneous two-dimensional electron system breaks up into well confined stripes surfing the wave. As a result, we observe a strong reduction of electronic sound attenuation. On the other hand, large momentum transfer between the electron system and the wave results in nonlinear acoustoelectric effects and acoustoelectric amplification. We describe our experimental findings in terms of a generalized theory of the acoustoelectric effect and discuss the importance for possible device applications. © 1999 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
43.25.-x Nonlinear acoustics
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
43.38.-p Transduction; acoustical devices for the generation and reproduction of sound
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
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Reversible charging effects in SiO2 films containing Si nanocrystals

Suk-Ho Choi and R. G. Elliman

Appl. Phys. Lett. 75, 968 (1999); http://dx.doi.org/10.1063/1.124569 (3 pages) | Cited 35 times

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Reversible charging effects are observed in metal–insulator–semiconductor structures which have been ion implanted and annealed to produce Si nanocrystals in the insulating SiO2 layer. The shifts in current–voltage (I–V) and capacitance–voltage (C–V) curves are induced by forward constant voltage stress or UV light exposure, and can be explained by hole charging of the nanocrystals in the insulator layer. A reverse constant voltage stress is shown to recover the original I–V curve and partially recover the original C–V curve. For a sample implanted with a Si dose of 3×1016 Si cm−2, the voltage shift of the I–V curve produced by a forward voltage stress of V = −10 V for 5 s is 1.2 V, which is shown to be in reasonable agreement with simple estimates based on nanocrystal charging. © 1999 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Rx Nanocrystalline materials

Anti-Stokes photoluminescence in colloidal semiconductor quantum dots

Ehud Poles, Donald C. Selmarten, Olga I. Mićić, and Arthur J. Nozik

Appl. Phys. Lett. 75, 971 (1999); http://dx.doi.org/10.1063/1.124570 (3 pages) | Cited 38 times

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We report anti-Stokes photoluminescence (photon energy up-conversion) from size-quantized CdSe and InP nanocrystalline colloids. The observed up-conversion is highly efficient and occurs at very low excitation intensities. With low temperatures the intensity of the up-converted photoluminescence decreases while that of the usual Stokes photoluminescence increases; the up-converted photoluminescence is also restricted to energies corresponding to the band gaps of the quantum dots that are present in the colloid ensemble. The anti-Stokes photoluminescence is explained by a model that involves surface states. © 1999 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.55.Cr III-V semiconductors
78.66.Hf II-VI semiconductors
78.66.Fd III-V semiconductors
82.70.Dd Colloids
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Luminescence of ZnCdSe/ZnSe ridge quantum wires

W. Heiss, G. Prechtl, D. Stifter, H. Sitter, G. Springholz, T. Riemann, F. Bertram, D. Rudloff, J. Christen, G. Bley, U. Neukirch, J. Gutowski, and J. Liu

Appl. Phys. Lett. 75, 974 (1999); http://dx.doi.org/10.1063/1.124571 (3 pages) | Cited 3 times

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Blue light-emitting quantum wire structures fabricated by molecular-beam epitaxial growth on submicrometer prepatterned GaAs substrates were investigated by spatially and time resolved luminescence experiments. The quantum wires are formed due to the different growth rates of ZnCdSe on the (111) and (100) surfaces of the grated substrate. With decreasing wire width, the exciton luminescence splits into two clearly distinguished lines. These lines can be assigned to the emission of the ridge quantum wire and the emission of ZnCdSe quantum wells at the bottom of the grooves. The two-dimensional quantum confinement in the ridge wire is confirmed by a maximum of the decay time at the energy of the ridge luminescence. © 1999 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.05.Dz II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.47.-p Spectroscopy of solid state dynamics
71.35.-y Excitons and related phenomena
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Depth-resolved microspectroscopy of porous silicon multilayers

S. Manotas, F. Agulló-Rueda, J. D. Moreno, R. J. Martín-Palma, R. Guerrero-Lemus, and J. M. Martínez-Duart

Appl. Phys. Lett. 75, 977 (1999); http://dx.doi.org/10.1063/1.124572 (3 pages) | Cited 19 times

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We have measured depth-resolved microphotoluminescence (PL) and micro-Raman spectra on the cross section of porous silicon multilayers to sample different layer depths. The PL emission band gets stronger, blueshifts, and narrows at the high porosity layers. On the contrary, the Raman band weakens and broadens. This band is fitted to the phonon confinement model. With the bulk silicon phonon frequency and its linewidth as free parameters, we obtain crystallite size, temperature, and stress as a function of depth. Sizes are larger than those estimated from PL. Laser power was reduced to eliminate heating effects. Compressive stresses in excess of 10 kbar are found in the deepest layer due to the lattice mismatch with the substrate. © 1999 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators

Structure and optical properties of ZnO/Mg0.2Zn0.8O superlattices

A. Ohtomo, M. Kawasaki, I. Ohkubo, H. Koinuma, T. Yasuda, and Y. Segawa

Appl. Phys. Lett. 75, 980 (1999); http://dx.doi.org/10.1063/1.124573 (3 pages) | Cited 188 times

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ZnO/Mg0.2Zn0.8O superlattices with a band-gap offset of about 0.5 eV were epitaxially grown by laser molecular-beam epitaxy on a sapphire(0001) substrate using a ZnO buffer layer. The superlattice structure with a period ranging from 8 to 18 nm was clearly verified by cross-sectional transmission electron microscopy, Auger depth profile, and x-ray diffraction. As the well layer thickness decreased below 5 nm, the photoluminescence peak and absorption edge in the photoluminescence excitation spectra showed a blueshift, indicating a quantum-size effect. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

SiGe-on-insulator substrate using SiGe alloy grown Si(001)

Yukari Ishikawa, N. Shibata, and S. Fukatsu

Appl. Phys. Lett. 75, 983 (1999); http://dx.doi.org/10.1063/1.124574 (3 pages) | Cited 27 times

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Low-energy oxygen ion (25 keV O+) implantation was performed on a pseudomorphic Si1−xGex/Si(001) of uniform composition in an attempt to create a SiGe-on-insulator (SiGe-OI) substrate using the separation-by-implanted-oxygen technique. Choosing a small Ge composition (<0.3) was found to be essential to achieving a SiGe-OI geometry of structural integrity. © 1999 American Institute of Physics.
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61.72.up Other materials
85.40.Ry Impurity doping, diffusion and ion implantation technology

Lasing in quantum-dot ensembles with sharp adjustable electronic shells

S. Fafard, Z. R. Wasilewski, C. Nì. Allen, K. Hinzer, J. P. McCaffrey, and Y. Feng

Appl. Phys. Lett. 75, 986 (1999); http://dx.doi.org/10.1063/1.124253 (3 pages) | Cited 35 times

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Quantum-dot laser diodes with up to five well-defined electronic shells are fabricated using self-assembled quantum dots (QDs) grown by molecular-beam epitaxy. Shape-engineered stacks of self-aligned QDs with improved uniformity are used to increase the gain in the active region. Lasing is observed in the upper QD shells for small-gain media, and progresses towards the QD ground states for longer cavity lengths. We obtained at 77 K thresholds of Jth = 15 A/cm2 for a 2 mm cavity lasing in the first excited state (p shell), and Jth = 125 A/cm2 for a 1 mm cavity lasing in n = 3 (d shell). At 300 K for a 1 mm cavity, Jth is 490 A/cm2 with lasing in n = 4 (f shell). © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Low-energy electron microscopy observations of GaN homoepitaxy using a supersonic jet source

A. Pavlovska, V. M. Torres, E. Bauer, R. B. Doak, I. S. T. Tsong, D. B. Thomson, and R. F. Davis

Appl. Phys. Lett. 75, 989 (1999); http://dx.doi.org/10.1063/1.124575 (3 pages) | Cited 8 times

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A study of the homoepitaxial growth of GaN(0001) layers was conducted in situ and in real time using the low-energy electron microscope. The Ga flux was supplied by an evaporative cell while the NH3 flux was supplied via a seeded-beam supersonic jet source. At growth temperatures of 665 °C and 677 °C, smooth GaN(0001) layers with well-defined step structures were grown on GaN(0001) substrates prepared by metalorganic chemical vapor deposition. In general, nonfaceted homoepitaxial layers were achieved when the Ga/NH3 flux ratios exceeded 2, starting with a Ga-covered substrate surface, in the temperature range of 655–710 °C. © 1999 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
68.55.-a Thin film structure and morphology

Growth of epitaxial silicon at low temperatures using hot-wire chemical vapor deposition

J. Thiesen, E. Iwaniczko, K. M. Jones, A. Mahan, and R. Crandall

Appl. Phys. Lett. 75, 992 (1999); http://dx.doi.org/10.1063/1.124576 (3 pages) | Cited 27 times

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We demonstrate epitaxial silicon growth of 8 Å/s at temperatures as low as 195 °C, using hot-wire chemical vapor deposition. Characterization by transmission electron microscopy shows epitaxial layers of Si. We briefly discuss various aspects of the process parameter space. Finally, we consider differences in the chemical kinetics of this process when compared to other epitaxial deposition techniques. © 1999 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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