Showing papers on "Cathodoluminescence published in 1987"

Process for the production of a display means by cathodoluminescence excited by field emission

Abstract: A process of producing a display operating by cathodoluminescence excited by field emission, including forming parallel cathodes on a glass substrate, depositing a silica coating on the cathodes, then a conductive coating and then producing a matrix of holes in the conductive coating and silica coating, depositing on the perforated conductive coating a fourth coating not covering the holes and then depositing on the complete structure a coating of an electron emitting material, eliminating the fourth coating so as to expose the microemitters, forming in the conductive coating grids crossing the cathodes and placing above the grids an anode covered by a cathodoluminescent coating.

Cathodoluminescence atomic scale images of monolayer islands at GaAs/GaAlAs interfaces

Abstract: Direct images of growth islands differing by 2.8 A [1 monolayer (ML)] height at GaAs/AlGaAs heterointerfaces and of the columnar structure of quantum wells are reported for the first time. The structures are grown by molecular‐beam epitaxy (MBE) with interruptions of the growth of ≊2 min at the interfaces. The method used to obtain these images is scanning cathodoluminescence. The dependence of the lateral extension of these islands on growth conditions is investigated. For fixed growth rate rs≊0.5 ML/s the mean island size decreases from 6–7 μm to 2 μm upon an increase of growth temperature from Tg=600 to 660 °C. Apparently the growth process changes from a planar to a three‐dimensional one. For low‐growth temperature and rate the lateral extension of such islands can be larger than the carrier diffusion length. Under these conditions interisland thermalization of carriers is largely suppressed. Quantitative information on the reduction of roughness of the quantum well interfaces with increasing growth i...

Luminescence Due to Radiative Transitions between Valence Band and Upper Core Band in Ionic Crystals (Crossluminescence)

Abstract: In some wide band gap halides of heavy alkali and alkaline-earth metals (BaF2, CsCl, RbF etc.) the energy separation between the valence band involving mainly the halogen electronic states and the upper cation core band is smaller than the band gap. Under the excitation generating holes in the core band radiative electronic transitions from the valence band to the core band take place giving rise to a specific kind of intrinsic emission which is proposed to call crossluminescence. Its decay time is about 1 ns and the thermal quenching starts at temperatures well above room temperature. The width of the emission spectrum practically coincides with the width of the valence band deduced from ultraviolet photoelectron spectroscopy and the shape of the spectrum depicts the electronic structure of the valence band. In einigen Alkali- und Erd-Alkalihalogeniden (BaF2, CsCl, RbF u. a.) ist die Energiedifferenz zwischen dem Valenzband und dem hochsten Atomrumpfband kleiner als die Energielucke. Unter hochenergetischer Strahlungsanregung, die Locher im Atomrumpfband generiert, treten strahlende elektronische Ubergange von Valenzband zum Atomrumpfband auf, eine spezifische Eigenlumineszenz, die „Crosslumineszenz” genannt wird. Die Abklingzeit dieser Lumineszenz ist etwa 1 ns und die thermische Tilgung beginnt uber Zimmertemperatur. Die Spektrumsbreite korreliert mit der Valenzbandbreite, wie durch Photoelektronenspektroskopie festgestellt wird, und die Struktur des Spektrums charakterisiert die Elektronenstruktur dieses Valenzbandes.

Stress variations due to microcracks in GaAs grown on Si

Abstract: Luminescence studies of thick (≥5 μm) GaAs epitaxial layers grown on Si substrates reveal regions of nonuniform stress associated with the presence of microcracks. Using cathodoluminescence spectroscopy as a tool for microcharacterization, the magnitude of the stress, derived from the peak positions of the luminescence spectra, is shown to increase gradually as a function of distance from the intersection of two microcracks. The greatest degree of stress relief was found at this intersection.

Interface structure and optical properties of quantum wells and quantum boxes

Abstract: We investigate two types of GaAs–GaAlAs interfaces in single quantum wells: (a) The abrupt interface produced by growth interruption during molecular‐beam epitaxy; (b) the interdiffused interface produced by Ga+ ion implantation and annealing. The abrupt interfaces are shown to contain islands with sizes ≲1.5 μm. The ion implanted and interdiffused interfaces are characterized by an error function Al concentration profile. The Ga and Al interdiffusion is found to be markedly enhanced (up to ≊100 times at 900 °C) following the ion implantation and annealing. Quantum well boxes (QWB) are produced using the implantation enhanced interdiffusion (IEI) process. The new cathodoluminescence spectral lines observed in the analysis of QWB’s are attributed to three‐dimensional carrier confinement in the potential wells induced by locally enhanced interdiffusion.

Isotope shifts of nitrogen-related localised mode vibrations in diamond

Abstract: Cathodoluminescence studies of the 3.188 eV vibronic band in 12C and 13C synthetic diamonds show that the sharp peaks at around 3.0 eV are local-mode replicas of the zero-phonon line. Accurate measurement of the isotope shifts shows that one of these modes involves the vibration of a single nitrogen atom. This interpretation is confirmed by measurements on 15N-doped synthetic diamond. A vibrational absorption peak at 1856 cm-1, superimposed on the tail of the two-phonon lattice band, is shown, from vacancy-enhanced aggregation studies on 15N-doped diamond, to be a di-nitrogen centre.

Carrier confinement potential in quantum-well wires fabricated by implantation-enhanced interdiffusion in the GaAs-Ga1-xAlxAs system.

Abstract: We compute the shape of the confinement potential resulting from the interdiffusion of a GaAs quantum well locally enhanced by defects due to gallium implantation. We use the simplest model taking into account the lateral diffusion of the defects. A variational calculation of the first two electronic levels within this two-dimensional potential supports the assignment of the recently observed new cathodoluminescence lines to electrons laterally confined in a graded potential.

Be incorporation in heavily doped molecular beam epitaxy grown GaAs: Evidence of nonradiative behavior by cathodoluminescence and electron acoustic measurements

Abstract: Cathodoluminescence and electroacoustic detection have been used for the characterization of Be‐doped GaAs epilayers grown by molecular beam epitaxy for the doping levels greater than 6.5×1017 at. cm−3. The Be concentration dependence of cathodoluminescence intensity as well as electron acoustic intensity shows the presence of nonradiative centers for concentrations greater than 1018 at. cm−3. Besides, extended defects and doping striations are revealed by electron acoustic images for heavily Be‐doped GaAs (1020 at. cm−3).

Cathodoluminescence decay time studies of the neutral vacancy in diamond

Abstract: The decay of GR1 cathodoluminescence associated with the neutral vacancy in diamond has been studied in the temperature range 10 to 77 K. Exponential decay of the luminescence is only obtained when short (5 ns) widely spaced (10 mu s) pulses are used, yielding a decay time of 3.1 ns in the temperature range studied. If much longer excitation pulses are used (10 mu s at 10 kHz), or a higher duty cycle (100 ns at 1 MHz), additional structure is observed in the zero-phonon region of the luminescence spectrum identical with that obtained using continuous excitation. Under these conditions the luminescence decay is slower and non-exponential. The value of 3.1 ns, obtained using short widely spaced pulses, is therefore expected to represent the upper limit for the radiative decay time of the centre, and compares with a decay time of 2.55 ns obtained using photo-excitation. Differences between the cathodoluminescence and photoluminescence spectra, and the complex decay of the former, are attributed to the indirect excitation mechanism, rather than to saturation effects.

Characterization of Zirconia/Mullite Ceramics by Cathodoluminescence Technique

Abstract: Characterization of mullite-ZrO2 ceramics by Cathodoluminescence (CL) technique has been made. The analyses of the CL emission show complex spectra with broad and sharp bands. An attempt has been carried out to relate these bands to the main constitutive phases in the samples. Spatial distribution of the CL is found to be inhomogeneous.

Influence of {111} regrowth sidewall interfaces on the performance of 1.54 μm InGaAsP/InP etched‐mesa‐buried‐heterostructure lasers

Abstract: The quality of {111} sidewall interfaces formed during liquid phase epitaxial regrowth around an etched mesa in an etched‐mesa‐buried‐heterostructure laser device has been studied using cross‐sectional transmission electron microscopy, cross‐sectional transmission cathodoluminescence, and energy dispersive x‐ray analysis. The results are correlated with the optical performance and electrical characteristics of the device before the aging test. It is found that the interfacial lattice imperfection will affect the device performance only when the defects are nonradiative recombination centers or they constitute a leakage path for the current. The possible causes for a defective interface will be discussed.

Dislocation gettering in semi‐insulating GaAs investigated by cathodoluminescence

Abstract: The cathodoluminescence (CL) imaging technique is applied to the characterization of semi‐insulating GaAs substrates after an extrinsic gettering treatment. A reverse contrast CL image is found for the gettered material. This study provides evidence for the physical mechanism taking place in the gettering process and contributes to the understanding of the effect of dislocations on device performance.

Cathodoluminescence, gain, and stimulated emission in electron‐beam‐pumped ZnCdSe

Abstract: Cathodoluminescence and lasing properties of ZnCdSe were studied over a wide range of temperatures and excitation conditions in a demountable CRT. Lasing was obtained in the range of wavelengths from yellow to red. Based on the results of the experiments, gain and absorption spectra under different conditions were calculated. The band‐gap dependence on excitation density was studied and the results offered an explanation for the differences between dependencies of the threshold‐excitation densities on penetration depth at different temperatures.

Degradation in GaAs/AlGaAs double-heterostructure light-emitting diodes

Abstract: Degradation of GaAs/AlGaAs double‐heterostructure light‐emitting diodes under accelerated aging tests has been investigated through cathodoluminescence measurements. We observed an increase in intensity of the band‐edge emission and a decrease in that of defect‐related deep level emision for the cladding layers. As for the active layer, a decrease was observed in the intensity of the band‐edge emission. These results suggest that defects migrate gradually from the cladding layer into the active layer.

Optical emission properties of metal/InP and GaAs interface states

Abstract: We have measured optical emission from interface states formed by metal deposition on UHV‐cleaved InP(110) and GaAs(110) surfaces by means of cathodoluminescence spectroscopy. Our study reveals discrete levels distributed over a wide range of energies and localized at the microscopic interface. Our results demonstrate the influence of the metal, the semiconductor, and its surface morphology on the energy distributions. The detailed evolution of optical emission energies and intensities with multilayer metal deposition exhibits a strong correlation between the deep gap levels, the Fermi level movements, and Schottky barrier heights. The results demonstrate that in general electronic states deep within the band gap continue to evolve beyond monolayer coverage into the metallic regime.

Applications of cathodoluminescence of quartz and feldspar to sedimentary petrology.

Abstract: s with Programs, 5., 726. CL Applications of Quartz and Feldspar Mariano, A. N., Ring, P. J. ( 1975), Europium-activated cathodoluminescence in minerals. Geochim. et Cosmo. Acta, 3..9.,

Annealing behavior of Ga+ implanted GaAs/AlGaAs observed by transmission electron microscopy

Abstract: The structural aspects and annealing behavior of induced damage by Ga+ ion implantation of a GaAs single quantum well as investigated by transmission electron microscopy are presented. After rapid thermal annealing, vacancy and interstitial perfect dislocation loops are found on 〈110〉 and 〈111〉 type planes. In contrast to previous results from superlattices of AlGaAs/GaAs, we find dislocation loops in the AlGaAs as well as in the GaAs layer. The cathodoluminescence intensity of the implanted quantum well recovers completely after annealing.

Lateral Patterning of Quantum Well Structures through Compositional Mixing

Abstract: Impurity and crystal defect induced compositional disordering of GaAs/AlxGai_xAs layered structures offers new microfabrication possibilities. By ion implantation one can control the location of the mixed region and control the degree of mixing. Specimens in this study were implanted with aluminum or silicon at energies and doses to give similar implanted-ion profiles. These were examined by cross-sectional transmission electron microscopy, secondary ion mass spectroscopy, and cathodoluminescence. The samples implanted with Al were found to partially disorder at a depth centered around the maximum damage peak. Silicon was found to disorder the material more completely than Al, and the disordered region extended to a depth greater than two times the projectile range. The effects of different annealing conditions on the disordering are discussed. We also implanted samples through high resolution ion masks and studied the disorder profile by TEM. The study revealed that the lateral disorder front follows that expected from the straggle of implanted ions. The feasibility of patterning with lateral resolution better than 30 nm is demonstrated. We have observed structure in spatially resolved cathodoluminescence, which we believe to arise from reduced dimensionality laterally patterned quantum wells.

Cleavage-related electronic states of Al-InP(110) interfaces

Abstract: Cathodoluminescence spectroscopy studies of III–V compound semiconductor surfaces and their metal interfaces show that the optical emission of deep‐level surface and interface states depend on semiconductor‐surface morphology. Spatially resolved measurements reveal metal‐induced interface states at cleavage steps whose optical emission properties depend on electron‐beam injection level. The density and spatial distribution of such metal‐cleavage‐related states may account for variation in electronic measurements reported for clean III–V compound semiconductor/metal interfaces.

Study of silicon‐doped AlxGayIn1−x−yAs quaternary layers by localized cathodoluminescence and electron acoustic microscopy

Abstract: Silicon incorporation in Al019Ga028In053As quaternary layers grown by molecular‐beam epitaxy has been studied by low‐temperature (10‐K) cathodoluminescence and scanning electron acoustic microscopy The maximum attained electron concentration was 65×1018 at cm−3 For heavily doped samples, cathodoluminescence spectra show the presence of several deep levels and a very distinct structure in the near‐band‐edge transition Even when a maximum is observed for the near‐band‐edge cathodoluminescence emission, deep levels and electron acoustic signals increase as function of the silicon concentration

Cathodoluminescence of cadium diphosphide crystals

Abstract: An investigation is made of the Cathodoluminescence spectra of CdP2 crystals in the temperature range 6 to 300 K. A pulsing beam of high energy electrons (40 kV) is used in the experiment. The samples investigated are undoped, heat annealed in vacuum or saturated vapours of cadimum, and also doped with As an Bi, elements isoelectronic to phosphorus. The experimental results show that the fine structure present in the higher energy wing (2.02 to 2.14 eV) depends on the concentration of the uncontrolled nitrogen impurity in CdP2. Atoms of nitrogen give rise to exciton-impurity complexes, leading to intense narrow peaks in the spectrum of Cathodoluminescence. Their location and nature are shown in a table. [Russian Text Ignored].

The Formation and Cathodoluminescence Activity of Buffer Layer Edge Dislocations in In0.12Ga0.88As/GaAs Heterostructures

Abstract: The defect structure of lattice-mismatched one micron In 0.12 Ga 0.88 As epilayers on (001) GaAs was studied with scanning cathodoluminescence (CL) and transmission electron microscopy (TEM). CL examination of the GaAs buffer layer revealed the formation of a segmented network of defects below the interface. Cross-sectional TEM analysis shows that these defects are dislocation half-loops extending from the interface, and the vast majority of these loops lie on the GaAs side of the interface. The dislocations in the GaAs buffer layer were determined to be edge dislocations. Thus, CL images show that edge dislocations in this system are centers for non-radiative recombination. We propose that two 60° dislocations with opposite screw and interface tilt components can glide into the buffer layer to form edge dislocations. Potential energy plots for 60° dislocations near the interface and interacting with interface dislocations supports this model.