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29 Oct 2001

Volume 79, Issue 18, pp. 2865-3001

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Single-mode solid-state single photon source based on isolated quantum dots in pillar microcavities

E. Moreau, I. Robert, J. M. Gérard, I. Abram, L. Manin, and V. Thierry-Mieg

Appl. Phys. Lett. 79, 2865 (2001); http://dx.doi.org/10.1063/1.1415346 (3 pages) | Cited 253 times

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We report the fabrication of a single-mode solid-state single photon source, based on an isolated InAs quantum dot (QD) on resonance with the fundamental mode of a pillar microcavity. Photon correlation experiments under pulsed excitation reveal a clear antibunching behavior. We show that a preparation of the single photons in a given quantum state (same spatial mode, same polarization) can be obtained by placing a QD in resonance with the nondegenerate fundamental mode of an elliptical micropillar. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots
42.50.Dv Quantum state engineering and measurements

High-power and long-lifetime InAs/GaAs quantum-dot laser at 1080 nm

Hui-Yun Liu, Bo Xu, Yong-Qiang Wei, Ding Ding, Jia-Jun Qian, Qin Han, Ji-Ben Liang, and Zhan-Guo Wang

Appl. Phys. Lett. 79, 2868 (2001); http://dx.doi.org/10.1063/1.1415416 (3 pages) | Cited 28 times

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High power and long lifetime have been demonstrated for a semiconductor quantum-dot (QD) laser with five-stacked InAs/GaAs QDs separated by an InGaAs strain-reducing layer (SRL) and a GaAs spacer layer as an active medium. The QD lasers exhibit a peak power of 3.6 W at 1080 nm, a quantum slope efficiency of 84.6%, and an output-power degradation rate of 5.6%/1000 h with continuous-wave constant-current operation at room temperature. A comparative reliability investigation indicates that the lifetime of the InAs/GaAs QD laser with the InGaAs SRL is much longer than that of a QD laser without the InGaAs SRL. This improved lifetime of the QD laser could be explained by the reduction of strain in and around InAs QDs induced by the InGaAs SRL. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
78.67.Hc Quantum dots
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Emission uniformity and emission area of explosive field emission cathodes

D. Shiffler, M. Ruebush, M. LaCour, K. Golby, R. Umstattd, M. C. Clark, J. Luginsland, D. Zagar, and M. Sena

Appl. Phys. Lett. 79, 2871 (2001); http://dx.doi.org/10.1063/1.1415408 (3 pages) | Cited 24 times

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Explosive field emission cathodes have been used extensively in high power microwave tubes. These cathodes emit electrons without the use of cathode heaters. Recently, some theoretical and simulation work has been performed to gain further understanding of the physics of these cathodes. The purpose of this letter is to provide the experimental background and justification for the theoretical work. The general idea of how explosive field emission cathodes operate is that plasma is rapidly formed, which provides the sea of electrons for space charge limited flow. However, recent theoretical and experimental work suggests edge effects, rather than plasma formation across the entire emission area, can also provide the same effect. In this letter we review three types of cathodes which have been tested. We provide optical data on the cathode emission uniformity as well as the electrical data for the same devices. In particular, we find that a large percentage of the cathode can fail to take part in the emission process and yet the voltage and current can appear identical from the case in which the entire cathode contributes electrons to the emission process. © 2001 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
85.45.-w Vacuum microelectronics

Investigation of electronegativity in a radio-frequency Xe/SF6 inductively coupled plasma using a Langmuir probe

T. Kimura and K. Ohe

Appl. Phys. Lett. 79, 2874 (2001); http://dx.doi.org/10.1063/1.1414297 (3 pages) | Cited 5 times

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The ratio of negative ion to electron densities (electronegativity) has been investigated using a Langmuir probe technique in a radio-frequency Xe/SF6 inductively coupled plasma, where the electron density is in the order of 1016 m−3 and the electron and negative ion temperatures are about 3.5–5 and 0.4 eV, respectively, which are weakly dependent on SF6 content and power injected into plasma. The electronegativity, which is between 5 and 10, does not strongly depend on SF6 content, while it decreases gradually with the increase of electron density. © 2001 American Institute of Physics.
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52.25.-b Plasma properties
52.70.Ds Electric and magnetic measurements
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Identification of surface anion antisite defects in (110) surfaces of III–V semiconductors

Ph. Ebert, P. Quadbeck, K. Urban, B. Henninger, K. Horn, G. Schwarz, J. Neugebauer, and M. Scheffler

Appl. Phys. Lett. 79, 2877 (2001); http://dx.doi.org/10.1063/1.1408906 (3 pages) | Cited 6 times

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We identify surface anion antisite defects in (110) surfaces of GaAs, GaP, and InP using scanning tunneling microscopy combined with density-functional theory calculations. In contrast to subsurface arsenic antisite defects, surface antisite defects are electrically inactive and have a very localized defect state which gives rise to a distinct feature in scanning tunneling microscopy images. © 2001 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
71.55.Eq III-V semiconductors
61.72.J- Point defects and defect clusters
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Low-temperature growth of SiCAlN films of high hardness on Si(111) substrates

Radek Roucka, John Tolle, David J. Smith, Peter Crozier, I. S. T. Tsong, and John Kouvetakis

Appl. Phys. Lett. 79, 2880 (2001); http://dx.doi.org/10.1063/1.1413723 (3 pages) | Cited 7 times

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Thin films of metastable SiCAlN solid solution were deposited on Si(111) substrates at 550–750 °C, considerably below the miscibility gap of SiC and AlN phases at 1900 °C. Our low-temperature growth was based upon thermally activated reactions between a unimolecular precursor H3SiCN and Al atoms from an evaporative cell in a molecular-beam-epitaxy chamber. Characterization of deposited films by spectroscopic and microscopic techniques yielded near-stoichiometric composition throughout the columnar wurtzite structure with lattice parameters very close to those of 2H–SiC and hexagonal AlN. An average hardness of 25 GPa was measured for the SiCAlN films, comparable to that measured for sapphire. © 2001 American Institute of Physics.
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68.55.A- Nucleation and growth
68.60.Bs Mechanical and acoustical properties
62.20.Qp Friction, tribology, and hardness
81.05.Hd Other semiconductors
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Li Other semiconductors

Ultrafast electron trapping times in low-temperature-grown gallium arsenide: The effect of the arsenic precipitate spacing and size

P. A. Loukakos, C. Kalpouzos, I. E. Perakis, Z. Hatzopoulos, M. Logaki, and C. Fotakis

Appl. Phys. Lett. 79, 2883 (2001); http://dx.doi.org/10.1063/1.1413219 (3 pages) | Cited 8 times

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The role and interplay of basic structure parameters of arsenic precipitates on the ultrafast trapping of conduction band electrons has been studied in a series of low-temperature-grown GaAs epilayers grown at various temperatures ranging from 170 up to 325 °C and annealed at 600 °C. Cross sectional electron-transmission characterization was used to determine the density and size of the precipitated arsenic clusters with growth temperature. The dependence of the electron trapping times (τ) on the spacing (R) and radius (α) of the arsenic precipitates has been systematically studied by time-resolved pump-probe transient transmission spectroscopy. The present work demonstrates that the electron trapping time follows a τ∝R3/α law. © 2001 American Institute of Physics.
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73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
64.75.-g Phase equilibria
78.47.-p Spectroscopy of solid state dynamics
78.66.Fd III-V semiconductors

Optical emission from ultrathin strained type-II InP/GaP quantum wells

F. Hatami, G. Mussler, M. Schmidbauer, W. T. Masselink, L. Schrottke, H.-Y. Hao, and H. T. Grahn

Appl. Phys. Lett. 79, 2886 (2001); http://dx.doi.org/10.1063/1.1414291 (3 pages) | Cited 6 times

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We describe the growth and optical emission from ultrathin strained InP quantum wells grown on GaP substrates using gas-source molecular-beam epitaxy. The InP thickness was varied between 0.5 and 1.6 monolayers. Intense photoluminescence was emitted from the structures; time-resolved measurements indicate rather long carrier lifetimes of about 19 ns. With decreasing InP coverage, the emission lines are shifted from 2.18 to 2.28 eV due to quantum size effects. We explain the emission as spatially indirect recombination of electrons from the GaP X valleys with holes in InP and its phonon replicas. © 2001 American Institute of Physics.
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68.65.Fg Quantum wells
73.63.Hs Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.67.De Quantum wells
78.55.Cr III-V semiconductors
68.35.Ja Surface and interface dynamics and vibrations
78.47.-p Spectroscopy of solid state dynamics

Electron-beam-induced densification of Ge-doped flame hydrolysis silica for waveguide fabrication

S. Garcia Blanco, A. Glidle, J. H. Davies, J. S. Aitchison, and J. M. Cooper

Appl. Phys. Lett. 79, 2889 (2001); http://dx.doi.org/10.1063/1.1408903 (3 pages) | Cited 11 times

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Experimentally we compare the densification induced by electron beam irradiation of Ge-doped silica, produced by flame hydrolysis deposition with the densification of thermally produced SiO2. By comparing these results to the predictions made by elasticity theory, we find good agreement for the thermal SiO2 by considering a single region of electron beam damage. For the Ge-doped flame-hydrolysis-deposited silica, we need to include in the model a second, shallow region, which densifies to a greater extent. X-ray photoelectron spectroscopy measurements suggest that the thickness of this additional region is comparable to a layer that was found to be depleted of Ge. © 2001 American Institute of Physics.
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61.82.Ms Insulators
61.80.Fe Electron and positron radiation effects
42.79.Gn Optical waveguides and couplers
62.20.D- Elasticity
42.86.+b Optical workshop techniques
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

7Be tracer diffusion in a deeply supercooled Zr46.7Ti8.3Cu7.5Ni10Be27.5 melt

A. Rehmet, K. Rätzke, F. Faupel, P. D. Eversheim, K. Freitag, U. Geyer, and S. Schneider

Appl. Phys. Lett. 79, 2892 (2001); http://dx.doi.org/10.1063/1.1412589 (3 pages) | Cited 8 times

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Beryllium self-diffusion in the deeply supercooled state of a Zr46.7Ti8.3Cu7.5Ni10Be27.5 alloy has been studied by a radiotracer technique by employing the isotope 7Be in combination with ion-beam sectioning. The temperature dependence of the diffusivity D is Arrhenius like with D(T) = 102.6 m2 s−1 exp(−2.6 eV/kBT). The tracer diffusivities consistently extend the size dependence of the diffusion observed in the supercooled liquid state of this alloy to the smallest constituent, but are at variance with previously published results of chemical Be diffusion. © 2001 American Institute of Physics.
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66.10.C- Diffusion and thermal diffusion
61.25.Mv Liquid metals and alloys

Identification of aging mechanisms in the optical and electrical characteristics of light-emitting diodes

Otto Pursiainen, Norbert Linder, Arndt Jaeger, Raimund Oberschmid, and Klaus Streubel

Appl. Phys. Lett. 79, 2895 (2001); http://dx.doi.org/10.1063/1.1413721 (3 pages) | Cited 36 times

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We report new methods of identifying the effects of aging on the light–current (L–I) and current–voltage (I–V) characteristics of AlInGaP light-emitting diodes (LEDs). We believe that these methods are also applicable to other III–V compound semiconductors. We observe a broadening of the nonlinear range of the L–I characteristic accompanied by a shift to higher currents in the I–V characteristic. These features can be attributed to an increase of nonradiative recombination processes in the active layer. A second process, however, can lead to an increase of the LED output power. We conclude from an analysis of the current dependence that this process is due to a different mechanism. © 2001 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
85.60.Jb Light-emitting devices

Thermomagnetic detection of recrystallization in FeCoNbBCu nanocrystalline alloys

J. S. Blázquez, C. F. Conde, and A. Conde

Appl. Phys. Lett. 79, 2898 (2001); http://dx.doi.org/10.1063/1.1413957 (3 pages) | Cited 17 times

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The recrystallization process in FeCoNbBCu nanocrystalline alloys is evidenced from thermomagnetic results as a significant decrease in magnetization at the second crystallization stage. The lowering in the volume fraction of α-FeCo crystals indicates that some of these crystals contribute to the boride phases formed. Electron microscopy images reveal that the final microstructure consists of large crystals (∼500 nm) of a fcc (FeCo)23B6 phase and small crystals (∼20 nm) of bcc α-FeCo and of some boride phases as such (FeCo)2B. © 2001 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
75.50.Bb Fe and its alloys
61.46.-w Structure of nanoscale materials
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Observation of nitrogen vacancy in proton-irradiated AlxGa1−xN

Qiaoying Zhou, M. O. Manasreh, M. Pophristic, S. Guo, and I. T. Ferguson

Appl. Phys. Lett. 79, 2901 (2001); http://dx.doi.org/10.1063/1.1415422 (3 pages) | Cited 9 times

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The optical absorption spectra of nitrogen vacancy (VN) in proton-irradiated AlxGa1−xN samples are observed. The spectra obtained for samples with 0.55 ⩽ x ⩽ 1 exhibit a peak and a shoulder with their energy positions dependent on the Al mole fraction. The peak and shoulder in the optical absorption spectra were interpreted as transitions from the valence band to the VN energy levels located below the conduction band in samples with x>0.55. The results were used to extrapolate the VN energy level positions in samples with 0 ⩽ x ⩽ 0.55. A linear fit of the observed VN energy level yields E(VN) = 4.230+0.680x (eV) for all values of x. Thermal annealing of various samples shows that the total integrated area, which is directly proportional to the defect density, of the absorption band attributed to the nitrogen vacancy is decreased as the annealing temperature is increased. © 2001 American Institute of Physics.
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71.55.Eq III-V semiconductors
61.72.J- Point defects and defect clusters
78.40.Fy Semiconductors
61.72.Cc Kinetics of defect formation and annealing

Long-time stability of high-concentration copper complexes in silicon crystals

Minoru Nakamura

Appl. Phys. Lett. 79, 2904 (2001); http://dx.doi.org/10.1063/1.1415413 (3 pages) | Cited 6 times

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The stability of diffused Cu in silicon crystal was evaluated by measuring the changes of photoluminescence intensity of the 1.014 eV Cu center with long storage time. Although the solubility of Cu is known to be low (<0.1 atom/cm3), high concentrations (>1013 atom/cm3) of mobile Cu in various Cu complexes (including the Cu center) were always maintained during more than a two-year storage at room temperature without Cu precipitation for float-zone and Czochralski (Cz) crystals when carbon concentrations were not so high for the latter. The Cu center for Cz crystals decreased shortly after annealing due to oxygen-enhanced nucleation of Cu sinks. Different behaviors of the Cu center in different crystals were reasonably explained by analyzing the transformation of Cu atoms between the Cu complexes and sinks. © 2001 American Institute of Physics.
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71.55.Cn Elemental semiconductors
78.55.Ap Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing

Observation of crystallographic wing tilt in cantilever epitaxy of GaN on silicon carbide and silicon (111) substrates

T. M. Katona, M. D. Craven, P. T. Fini, J. S. Speck, and S. P. DenBaars

Appl. Phys. Lett. 79, 2907 (2001); http://dx.doi.org/10.1063/1.1415039 (3 pages) | Cited 30 times

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We have characterized the growth of GaN on both SiC and Si (111) using the cantilever epitaxy technique. Cantilever epitaxy employs growth from periodic, parallel mesas which are formed by etching the substrate [C.I.H. Ashby et al. Appl. Phys. Lett. 77, 3233 (2000)]. GaN/AlN/Si and GaN/AlN/SiC layers were grown via metalorganic chemical vapor deposition on substrates with reactive ion etched trenches. This single step approach allows GaN to laterally overgrow the substrate trenches yielding low defect density material over the trench, while avoiding use of a mask which is commonly employed in lateral epitaxial overgrowth. Scanning electron microscopy, atomic force microscopy, and x-ray diffraction were used to characterize the resulting material. Significant threading dislocation reduction was observed in the “wing” regions (the material directly over the trenches). Contrary to previous reports, crystallographic wing tilt ranging from 0.22° to 0.77° was also observed, despite the absence of a wing/mask interface using this technique. © 2001 American Institute of Physics.
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68.55.A- Nucleation and growth
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Ps Atomic force microscopy (AFM)

Simple method for measuring the azimuthal anchoring strength of nematic liquid crystals

João G. Fonseca and Yves Galerne

Appl. Phys. Lett. 79, 2910 (2001); http://dx.doi.org/10.1063/1.1415344 (3 pages) | Cited 11 times

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We present a simple method for measuring the azimuthal anchoring strength and the angular gliding of nematic liquid crystals at the surface of solid substrates. The method only needs symmetrical samples. It uses the averaging of the interference oscillations when using white light, which allows one to measure the azimuthal deviation angle at the surface δφ directly from the polarizers angles at the minimum of light. It is then easy to determine the azimuthal extrapolation length ξφ on varying the cell thickness, e.g., by means of wedge cells. As an example, we measure the azimuthal anchoring strength of 5CB onto self-assembled monolayers deposited onto polished indium–tin–oxide. © 2001 American Institute of Physics.
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61.30.-v Liquid crystals
78.20.Fm Birefringence

Resonant scattering in delta-doped heterostructures

I. K. Robinson, P. O. Nilsson, D. Debowska-Nilsson, W. X. Ni, and G. V. Hansson

Appl. Phys. Lett. 79, 2913 (2001); http://dx.doi.org/10.1063/1.1415352 (3 pages) | Cited 5 times

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We demonstrate the utility of resonant x-ray scattering in probing the structure of doping layers at a heterostructure interface. The positions of germanium layers inserted at the interface of a silicon epitaxial film assert a strong influence of the phase of the scattered intensity along the crystal truncation rods. The phase of the scattering, and hence the internal structure of the layers, can be determined conveniently by analyzing its energy dependence in the vicinity of the Germanium absorption edge at 11.103 keV. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.66.Db Elemental semiconductors and insulators
78.70.Ck X-ray scattering
61.72.S- Impurities in crystals
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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Polarization charges and polarization-induced barriers in AlxGa1−xN/GaN and InyGa1−yN/GaN heterostructures

L. Jia, E. T. Yu, D. Keogh, P. M. Asbeck, P. Miraglia, A. Roskowski, and R. F. Davis

Appl. Phys. Lett. 79, 2916 (2001); http://dx.doi.org/10.1063/1.1412594 (3 pages) | Cited 6 times

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Polarization charges are measured and the formation of large electrostatic barriers arising primarily as a consequence of the presence of polarization-induced charge densities is deduced from capacitance–voltage analysis of n-type AlxGa1−xN/GaN and InyGa1−yN/GaN heterostructures. In structures consisting of 5–10 nm AlxGa1−xN or InyGa1−yN surrounded by n-GaN, capacitance–voltage profiling studies combined with elementary electrostatic analysis yield experimental estimates of polarization charge densities, which are compared with values expected based on the combined effects of spontaneous and piezoelectric polarization. These results imply the existence of electrostatic barriers that are due primarily to the large polarization charge densities at each heterojunction interface and the resulting potential difference maintained across the thin AlxGa1−xN or InyGa1−yN layers. The electrostatic barriers formed in these structures are large in comparison to the heterojunction conduction-band offsets, demonstrating the utility of polarization-based engineering of electrostatic barriers in nitride semiconductor heterostructures. © 2001 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Electric field-induced junctions in epitaxial layers of CuInSe2

Konstantin Gartsman, David Cahen, and Roland Scheer

Appl. Phys. Lett. 79, 2919 (2001); http://dx.doi.org/10.1063/1.1415040 (3 pages) | Cited 2 times

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Epitaxial films of CuInSe2 on Si(111) were modified by the application of an electric field through a movable tip. The electric field induces stable junction regions which are identified by efficient separation and collection of electron beam-induced charge carriers. The movable tip allows for scribing of these junction regions. The junctions can be explained by symmetrical p/p+/n/p+/p regions formed within the CuInSe2 epilayers. The reported method presents an alternate way for junction patterning in two dimensions. © 2001 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.05.Hd Other semiconductors

Defect annealing in Cu(In,Ga)Se2 heterojunction solar cells after high-energy electron irradiation

A. Jasenek, H. W. Schock, J. H. Werner, and U. Rau

Appl. Phys. Lett. 79, 2922 (2001); http://dx.doi.org/10.1063/1.1415345 (3 pages) | Cited 12 times

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Cu(In,Ga)Se2/CdS/ZnO solar cells need at least 1018 cm−2 electrons of an energy of 1 MeV to degrade in their power conversion efficiency by more than 25%. Even after such high irradiation doses, annealing of the irradiated solar cells at temperatures between 130 and 160 °C leads to a full recovery of the device performance. Isochronal annealing experiments unveil that the annealing of the irradiation-induced defects has an activation energy of 1.05 eV. © 2001 American Institute of Physics.
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84.60.Jt Photoelectric conversion
61.72.Cc Kinetics of defect formation and annealing

Low-resistance and high-transparency Ni/indium tin oxide ohmic contacts to p-type GaN

Ray-Hua Horng, Dong-Sing Wuu, Yi-Chung Lien, and Wen-How Lan

Appl. Phys. Lett. 79, 2925 (2001); http://dx.doi.org/10.1063/1.1415048 (3 pages) | Cited 78 times

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The characteristics of Ni/indium tin oxide (ITO) ohmic contacts to p-type GaN ( ∼ 2×1017 cm−3) have been studied. The Ni/ITO (10 nm/250 nm) layers were prepared by thermal evaporation and rf magnetron sputtering, respectively. Although the as-deposited Ni/ITO contacts present rectified behavior, the linear current–voltage characteristics can be obtained. The contact resistance can be reduced significantly for the ITO/Ni/p-GaN samples after suitable rapid thermal process. The contact property of ITO/Ni/p-GaN shows lowest specific contact resistivity of 8.6×10−4 Ω cm2 and high transparency (above 80% for 450–550 nm) as the sample annealed at 600 °C in air. Possible mechanisms for the observed low contact resistance and high transparency will be discussed. The present process is compatible with the fabrication for the high-efficient GaN light-emitting devices. © 2001 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.Cc Kinetics of defect formation and annealing

Strain relief by long line defects in tensile GaxIn1−xP layers grown on InP substrates

M. Kahn and D. Ritter

Appl. Phys. Lett. 79, 2928 (2001); http://dx.doi.org/10.1063/1.1412587 (3 pages) | Cited 1 time

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Fully strained layers of GaInP on InP significantly thicker than the theoretical critical thickness were grown by metalorganic molecular beam epitaxy. The excess strain energy of these layers is most probably accommodated by long line defects observed by atomic force microscopy. The thickness at which the long line defects appear is about four times the Matthews and Blakeslee critical thickness [J. W. Matthews and A. E. Blakeslee, J. Cryst. Growth 27, 118 (1974)]. Partial relaxation is measured by x-ray at about 14 times the theoretical critical thickness. © 2001 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Lk Linear defects: dislocations, disclinations
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Very-low-energy electron microscopy of doped semiconductors

M. M. El-Gomati and T. C. R. Wells

Appl. Phys. Lett. 79, 2931 (2001); http://dx.doi.org/10.1063/1.1415045 (3 pages) | Cited 22 times

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Imaging of As- and B-doped silicon regions has been performed in a scanning electron microscope operated in the cathode lens mode, with incident electron energies (EP) as low as 15 eV. The doped regions of n+ (As, 2.5×1020 cm−3) and p+ (B, 8×1019 cm−3) on n-type silicon ( ∼ 1015 cm−3) show distinct contrast with electron energies of about 3 keV. The brightest region is n+ followed by p+, then the n-type substrate. The highest contrast for the p+ and n+ type regions is reached at about EP = 300 and 15 eV, respectively. The contrast mechanisms are explained in terms of metal-semiconductor contact assuming an adventitious carbon film at the surface. © 2001 American Institute of Physics.
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68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
61.72.uf Ge and Si
79.20.Fv Electron impact: Auger emission
68.49.Jk Electron scattering from surfaces
73.40.Ns Metal-nonmetal contacts
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Mass-density-modulated structures of crystalline hydrogenated carbon films

Z. J. Zhang, K. Narumi, and H. Naramoto

Appl. Phys. Lett. 79, 2934 (2001); http://dx.doi.org/10.1063/1.1411990 (3 pages)

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Hydrogenated carbon films with a crystalline structure have been synthesized by radio-frequency plasma-enhanced chemical vapor deposition. The mass density of the films is dependent on the plasma power applied. By switching alternatively two different plasma powers during deposition, mass-density-modulated structures of the crystalline hydrogenated carbon films can be produced. The structure and properties of these mass-density-modulated structures have also been investigated. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
68.60.Bs Mechanical and acoustical properties

Recombination activity of copper in silicon

R. Sachdeva, A. A. Istratov, and E. R. Weber

Appl. Phys. Lett. 79, 2937 (2001); http://dx.doi.org/10.1063/1.1415350 (3 pages) | Cited 27 times

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The carrier recombination activity of copper in n-type and p-type silicon has been investigated. The minority carrier diffusion length has been found to decrease monotonically with increasing copper concentration in n Si and to exhibit a step-like behavior in p-type silicon at Cu concentrations above a certain critical level. It is suggested that the impact of copper on the minority carrier diffusion length is determined by the formation of copper precipitates. This process is retarded in perfect silicon due to the large lattice mismatch between Cu3Si and the silicon lattice and even more retarded in p Si, due to electrostatic repulsion effects between the positively charged copper precipitates and interstitial copper ions. Comparison of the impact of Cu on minority carrier diffusion length obtained with p-Si samples of different resistivity confirmed the electrostatic model. Studies of the impact of copper on minority carrier diffusion length in samples with internal gettering sites indicated that they provide heterogeneous nucleation sites for Cu precipitation at subcritical Cu concentration. Above a certain threshold of Cu concentration, the bulk recombination activity is dominated by quasihomogeneous formation of Cu precipitates, a process that is not detectably affected by the presence of oxide precipitates. © 2001 American Institute of Physics.
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72.80.Cw Elemental semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
64.75.-g Phase equilibria
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