Showing papers on "Cathodoluminescence published in 1984"
TL;DR: In this article, a correlation between impurity trapping and the interface structure in GaAs quantum well (QW) superlattices and single quantum well structures grown by molecular beam epitaxy (MBE) on (100) GaAs was demonstrated.
Abstract: A correlation has been demonstrated between impurity trapping and the interface structure in GaAs quantum well (QW) superlattices and single quantum well structures grown by molecular beam epitaxy (MBE) on (100) GaAs. Using low‐temperature cathodoluminescence, photoluminescence, and transmission electron miscroscopy, we have shown that interface roughness in QW superlattices is related to trapped impurities at interfaces. We have observed that impurities originate from either the substrate or from the GaAlAs MBE layers. A new getter smoothing effect associated with QW structures is shown to produce efficient impurity trapping and yield higher quality GaAs QW with atomically smooth interfaces.
162 citations
TL;DR: In this paper, a cathodoluminescence detector attached to a transmission electron microscope has been used to record visible optical-emission spectra from individual dislocations of known type in type IIb diamond over a range of temperatures.
Abstract: A cathodoluminescence detector attached to a transmission electron microscope has been used to record visible optical-emission spectra from individual dislocations of known type in type IIb diamond over a range of temperatures. The polarization of the emission has also been determined from individual dislocations and this information correlated with the type and degree of dissociation of the dislocations. It was found that the dislocation emission at 435 nm was polarized along the dislocation line (independent of the Burgers vector) and had maximum intensity at 170 K. The emission spectrum was independent of dislocation type, and showed a broad (0·416 eV f.w.h.m.) band. All luminescent dislocations were dissociated, and one non-luminescent dislocation was found which was undissociated within the resolution of the weak-beam technique (∼ 15 A). Non-luminescent dissociated dislocations were also found. Curved dislocations were less luminescent than straight ones. A one-dimensional donor-acceptor mod...
116 citations
TL;DR: In this article, the transition rate of excitonic e −h recombination in GaAs quantum wells was found to increase by almost one order of magnitude upon a decrease of the well width from infinity to 52 A due to increased exciteonic localization.
Abstract: The transition rate of excitonic e‐h recombination in GaAs quantum wells is found to increase by almost one order of magnitude upon a decrease of the well width from infinity to 52 A due to increased excitonic localization. Competing capture of free carriers by impurities is increasingly suppressed. Time delayed cathodoluminescence spectra and decay times taken at 5–300 K show this unambiguously. Transfer of carriers from 176‐A Ga0.6Al0.4As cladding wells is found to occur ballistically in 10−13 s.
91 citations
TL;DR: In this article, single crystals of undoped and cerium-doped yttrium aluminum garnet have been pumped with laser radiation of 220 and 266 nm wavelength, and a broadband defect emission at approximately 300 nm was observed, similar to that obtained with cathodoluminescence.
Abstract: Single crystals of undoped and cerium‐doped yttrium aluminum garnet have been pumped with laser radiation of 220‐ and 266‐nm wavelength. A broadband defect emission at approximately 300 nm was observed, similar to that obtained with cathodoluminescence, although decreased in magnitude. Evidence of a transfer of energy from these defect states to the Ce+3 states was inferred from the photoluminescence decay time measurements. We have associated the absorption spectra from 200–300 nm with the defect excitation spectrum, including the peaks at 225 and 270 nm.
83 citations
TL;DR: The cathodoluminescence of single crystals of CuInSe2 obtained by melt-grown and iodine chemical transport was studied in this article, where the emission intensity decreases when the conductivity changes from n to p and then increases due to the decrease of the number of donors created by Se vacancies.
Abstract: The cathodoluminescence of single crystals of CuInSe2 obtained by melt‐grown and iodine chemical transport was studied. As‐grown crystals and crystals annealed in Se, In, or in a vacuum were used. We show the emission intensity decreases when the conductivity changes from n to p and then increases due to the decrease of the number of donors created by Se vacancies. We also show that two donor levels (60 and 80 meV) are introduced by the Se vacancy probably associated with impurities, and that the cation (probably Cu) vacancy causes an acceptor level at 40 meV. Another acceptor level is also determined, having a binding energy ≳80 meV.
53 citations
TL;DR: In this paper, the effects of substrate temperature and the group V to group III flux ratio during growth on the electrical properties and on the 4 K cathodoluminescence are reported.
Abstract: Al1−xInxAs films have been grown by molecular beam epitaxy (MBE) on InP substrates. Unintentionally doped material had a free electron concentration of the order of 1×1016 cm−3 when grown above 560 °C but was semi‐insulating when grown below 520 °C. The effects of substrate temperature and the group V to group III flux ratio during growth on the electrical properties and on the 4 K cathodoluminescence are reported. The Auger electron spectroscopy (AES) profiles through the films show that loss of indium is detectable only at temperatures in excess of 600 °C for As4/group III flux ratios of 15–20:1. The optimum MBE growth temperature for Al1−xInxAs on InP is 580 °C. Cathodoluminescence spectroscopy was used to measure the band gap of the epitaxial layers as a function of In content for values of x between 0.46 and 0.55. Over this range, at room temperature the band gap energy was found to vary as Eg(300 K)=1.450+2.29(0.523−x) eV, while at 4 K the relation was measured to be Eg(4 K)=1.508+2.22(0.523−x) eV. ...
47 citations
TL;DR: In this article, the growth temperature dependence of crystallographic and luminescent properties of ZnSe, ZnS and Zns x Se 1−x epilayers on GaAs was investigated.
44 citations
TL;DR: In this article, the main residual impurity, carbon, is not distributed homogeneously within the material, which may lead to nonuniformities in the electrical properties of the material.
Abstract: Characterization of semi‐insulating liquid encapsulated Czochralski GaAs by cathodoluminescence in a scanning electron microscope at liquid He temperatures has revealed that the main residual impurity, carbon, is not distributed homogeneously within the material. This may lead to nonuniformities in the electrical properties of the material.
34 citations
TL;DR: In this paper, the growth of AlGaAs/GaAs single quantum well (QW) heterostructures by metalorganic chemical vapor deposition (MOCVD) has been studied by varying the growth rate, growth temperature, and III/V ratio as well as by varying substrate type and the "interrupt time" used to grow the quantum wells.
29 citations
TL;DR: In this article, the GaAs−AlxGa1−xAs single and multiquantum well structures grown by metalorganic chemical vapor deposition have been examined for the first time in detail using low-temperature photoluminescence and transmission electron microscopy.
Abstract: GaAs‐AlxGa1−xAs single and multiquantum well structures grown by metalorganic chemical vapor deposition have been examined for the first time in detail using low‐temperature photoluminescence, cathodoluminescence, and transmission electron microscopy. The better heterointerfaces are very uniform with a large scale roughness of approximately plus or minus a monolayer along the interface on a scale of the exciton diameter or larger and a composition gradient width of less than three monolayers across the interface. The GaAs well interface roughness and associated impurity luminescence are not very sensitive to the thickness of the AlxGa1−xAs prelayer. With nonoptimum growth conditions, the quantum well photoluminescence characteristics suggest a substantial amount of band filling due to holes presumably from the AlxGa1−xAs layers.
27 citations
TL;DR: In this paper, Miyazawa et al. compared the cathodoluminescence (CL) uniformity of both Cr•doped and undoped SI GaAs crystals grown by liquid-encapsulated Czochralski (LEC) and horizontal gradient freeze (HGF) techniques.
Abstract: Miyazawa et al. [Appl. Phys. Lett. 43, 853 (1983)] have recently established a spatial correlation between variations in field‐effect transistor performance and nonuniformities in the cathodoluminescence (CL) efficiency of semi‐insulating (SI) GaAs substrates. In this study, we compare the CL uniformity of both Cr‐doped and undoped SI GaAs crystals grown by the liquid‐encapsulated Czochralski (LEC) technique with undoped SI crystals grown by the horizontal gradient freeze (HGF) technique. In contrast to the LEC crystals, HGF GaAs has extremely uniform CL characteristics which should result in uniform device performance.
TL;DR: A radiative bound exciton transition at 1.36 eV has been observed in the low temperature cathodoluminescence spectrum emitted from InP grown epitaxially by both molecular beam epitaxy (MBE) and by metal-organic chemical vapour deposition (MOCVD) under certain specific growth conditions.
Abstract: A radiative bound exciton transition at 1.36 eV has been observed in the low temperature cathodoluminescence spectrum emitted from InP grown epitaxially by both molecular beam epitaxy (MBE) and by metal-organic chemical vapour deposition (MOCVD) under certain specific growth conditions. In both growth techniques the conditions give rise to a depletion of phosphorus in the epilayers and it is suggested that the defect binding the excitons may be a complex incorporating a phosphorus vacancy.
TL;DR: In this paper, secondary electron emission spectroscopy was used to study the surface electronic and vibrational properties of fine and defective MgO(100) surfaces under ultra-high vacuum.
Abstract: Surface electronic and vibrational properties of “fine” and “defective” MgO(100) surfaces have been studied by secondary electron emission spectroscopy applying the electron time-of-flight method and cathodoluminescence spectroscopy under ultra-high vacuum. The energies of the bottom of the conduction band and a level related closely to the F center in MgO are determined to be 4.0 and 1.6 eV above the vacuum level, respectively. Work function, which is the energy difference between the vacuum level and the top of the valence band, of MgO is determined to be 3.8 eV. In the “defective” crystal, the phonon side band due to electron-phonon coupling is resolved around the extra peak at 1.6 eV in the secondary electron emission.
TL;DR: The formation of dark spot defects (DSDs) in InP InGaAsP aged light emitting diodes has been investigated by spatially resolved cathodoluminescence, transmission electron microscopy and Rutherford backscattering as mentioned in this paper.
TL;DR: In this paper, the time dependences of local cathodoluminescence (CL) intensity for some materials and a CL contrast of direct writing patterns by means of the scanning electron microscope (SEM) have been investigated.
TL;DR: A theoretical treatment of binary compound cathodoluminescence efficiency on the basis of the statistical model treating the branching process of ionization scattering and phonon emission is given in this paper.
Abstract: A theoretical treatment is given of binary compound cathodoluminescence efficiency on the basis of the statistical model treating the branching process of ionization scattering and phonon emission. Energy loss mechanisms of hot electrons in semiconductors are quantitatively examined using Penn’s model assuming an optical phonon deformation potential and polar‐mode electron‐phonon interactions. The quantum yield of e‐h pairs is calculated with three parameters, the band‐gap energy Eg, and two loss parameter constants Sd and Sp which are determined completely in terms of material parameters including Eg, the mass density, the lattice constant, the covalency, the optical phonon frequency, and dielectric constants. The material characterization of efficient phosphors is discussed in terms of empirical correlations between cathodoluminescence efficiency and the physical constants. Dependence of efficiency on the crystal structure of the phosphor host is particularly noticeable. Comparisons are made with previo...
TL;DR: In this article, the authors showed that the cathodoluminescence brightness of Ca-doped Y 2 O 2 S is 10% of that of yellow-emitting (Zn, Cd)S: Ag.
TL;DR: In this paper, the authors used X-ray topography using both reflection and transmission geometry and scanning electron microscopy in the transmission cathodoluminescence mode to study a characteristic inclusion-like defect in InP single crystals grown by the liquid encapsulated Czochralski technique.
TL;DR: In this paper, the authors show that two emission bands appear: one at about 520 nm and another in the red region, and the last band has structures with a maximum located at 693 nm, probably associated with excited V3+ and Cr3+ respectively.
TL;DR: In this paper, the authors analyzed the cathodoluminescence (CL) emission of MgO single crystals after different treatments: thermochemical reduction, neutron irradiation, or quenching from high temperatures.
Abstract: Cathodoluminescence (CL) emission of undoped MgO single crystals, after different treatments: thermochemical reduction, neutron irradiation, or quenching from high temperatures is studied in the scanning electron microscope. In thermochemically reduced samples, two peaks at about 410 and 520 nm are observed. Neutron irradiated samples exhibit an emission band centered at 390 nm. The spectra of the quenched crystals show two peaks at around 420 and 490 nm. The results are analyzed on the basis of emission from F-type centers.
Es wird die Katodolumineszenz von undotierten MgO-Einkristallen nach verschiedenen Behandlungen: thermochemische Reduktion, Neutronenbestrahlung und Abschrecken, mittels Rasterelektronenmikroskopie untersucht. In den thermochemisch reduzierten Kristallen werden zwei Katodolumineszenz-Banden bei 410 und 520 nm beobachtet. Neutronenbestrahlte Kristalle zeigen eine Bande bei 390 nm und die abgeschreckten Kristalle zwei Emissionsbanden bei 420 und 490 nm. Die Ergebnisse werden auf der Basis der Emission von F-Typ-Zentren diskutiert.
TL;DR: In this paper, the effect of indentation and subsequent electron irradiation on the cathodoluminescence and photoluminecence was analyzed in hydrogen-doped MgO crystals.
Abstract: Cathodoluminescence studies of hydrogen-doped MgO crystals thermochemically reduced at high temperatures show that there is no direct correlation between the intensity of the cathodoluminescence and photoluminescence bands. These crystals contain anion vacancies and H− ions. Luminescence bands at 2·95 eV (420 nm) and 2·4 eV (520 nm) correspond to emission from the two charge states of the anion vacancies. In contrast to photoluminescence, the intensity of the latter cathodoluminescence band is much smaller than that of the former. The effect of indentation and subsequent electron irradiation on the cathodoluminescence and photoluminescence is described.
TL;DR: In this paper, three emission bands at 410, 525, and 580 nm have been observed in LiNbO3 single crystals and an intense emission with its peak in the infrared region has been observed.
Abstract: Cathodoluminescence (CL) emission from as‐grown, thermochemically reduced and mechanically damaged LiNbO3 single crystals has been studied in the scanning electron microscope. Three emission bands at 410, 525, and 580 nm have been observed. The CL spectra strongly depend on the deformation at the surface region. An intense emission with its peak in the infrared region has been observed. Severe damage is induced by irradiation with the electron microscope beam at very high current intensities.
TL;DR: MgS phosphors were prepared by reducing pure MgSO4 with CS2 and doped with Eu in this article, and the results on UV excitation, visible emission and IR stimulation were presented and discussed.
TL;DR: In this article, the cathodoluminescence of uranium oxide surfaces prepared in-situ from clean uranium exposed to dry oxygen was studied and the broad asymmetric peak observed at 470 nm was attributed to F-center excitation.
TL;DR: In this article, the origin of morphological defects on InGaAs was discussed and the technical solutions were used to reduce the defect density to less than 1×10 4 / cm 2.
TL;DR: In this paper, the presence of copper in various oxidation states can be attributed to the thermodynamics and kinetics of the system, and results correlating the observed interfacial microstructure and the thermochemistry of system are presented.
Abstract: The interfacial zones in copper-magnesium aluminosilicate materials were characterized by several microscopic and microchemical techniques. Interfaces between copper-glass, copper-partially crystallized glass, and copper-fully crystallized glass were studied with the specific goal of determining the oxidation state of copper in various locations in the microstructure of the reaction zones. Optical microscopy, cathodoluminescence, electron probe microanalysis (EPMA), SEM, TEM, and other microtechniques were used. The presence of copper in various oxidation states can be attributed to the thermodynamics and kinetics of the system. Results correlating the observed interfacial microstructure and the thermochemistry of the system are presented.
TL;DR: In this article, simultaneous transmission electron microscopy (TEM) and cathodoluminescence (CL) measurements have been performed on single dislocations in LEC InP.
Abstract: Simultaneous transmission electron microscopy (TEM) and cathodoluminescence (CL) measurements have been performed on single dislocations in LEC InP. The dislocations were found to exhibit differing luminescence behaviour. No enhancement of the near-band-edge or deep-level luminescence was observed at any of the dislocations but some of the dislocations caused the exciton luminescence to be quenched locally. The limited number of dislocations observed so far prevents any definite identification of the mechanism causing the exciton quenching.
TL;DR: In this paper, a relatively unsophisticated dispersive cathodoluminescence (CL) system attached to a scanning electron microscope (SEM) can be used expediently in the extensive study of such phosphors.
Abstract: The phenomenon of cathodoluminescence (CL) potentially offers the ideal tool for studying the phosphor materials used in fluorescent lamps, since it can be used directly on processed or unprocessed powders, on coatings in tubes, or on sections cut from tubes. Using examples of both single component materials and multi-component blends, it is demonstrated how a relatively unsophisticated dispersive CL system attached to a scanning electron microscope (SEM) can be used expediently in the extensive study of such phosphors. These studies can be significantly enhanced when other complementary modes of the SEM (e. g. the energy-dispersive x-ray analysis facility) are combined with the CL mode. The strength of the combined technique lies in the major role it can play in materials and processing aspects of the powders themselves, in the processing of the lamps (e.g. by optimising such parameters as coating thickness, packing density etc.), and in diagnostic studies of poor materials or lamps (e.g. by locating rogue particles/components and identifying their origin). The technique also provides a convenient method of studying the temperature stability of selected phosphors.
TL;DR: The technique of delayed coincidence has been used for the determination of cathodoluminescence lifetimes from various semiconductors, such as silicon and gallium arsenide as discussed by the authors.
Abstract: The technique of delayed coincidence has been used for the determination of cathodoluminescence lifetimes from various semiconductors. Results are presented of decay measurements performed on silicon (band-edge luminescence) and gallium arsenide (deep-level luminescence). These are 'materials systems' not usually associated with cathodoluminescence assessment techniques.