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Showing papers on "Photoluminescence published in 1986"


Journal ArticleDOI
TL;DR: In this article, the growth condition dependence of crystalline quality is also studied, and the narrowest x-ray rocking curve from the (0006) plane is 2.70' and from the 2024 plane is 1.86' on sapphire substrates.
Abstract: Atmospheric pressure metalorganic vapor phase epitaxial growth and characterization of high quality GaN on sapphire (0001) substrates are reported. Using AlN buffer layers, GaN thin films with optically flat surfaces free from cracks are successfully grown. The narrowest x‐ray rocking curve from the (0006) plane is 2.70’ and from the (2024) plane is 1.86’. Photoluminescence spectra show strong near band edge emission. The growth condition dependence of crystalline quality is also studied.

2,035 citations


Journal ArticleDOI
TL;DR: Single-photon- and multiphoton-induced luminescence spectra were obtained from clean samples of silver, copper, and gold with both smooth and rough surfaces and reveal new features which are correlated with interband transitions at selected symmetry points in the Brillouin zone.
Abstract: Single-photon- and multiphoton-induced luminescence spectra were obtained from clean samples of silver, copper, and gold with both smooth and rough surfaces. The spectra reveal new features which are correlated with interband transitions at selected symmetry points in the Brillouin zone. Calculating luminescence spectra based on simplified models of the band structures of the noble metals and taking into account the Fresnel local-field corrections, we find qualitative agreement with the observed spectra from smooth samples. The agreement between theory and experiment is less satisfactory for rough samples. The influence of surface roughness on the luminescence is largely attributable to local-field enhancement in the rough surface protrusions.

703 citations



Journal ArticleDOI
TL;DR: In this paper, GaAs and AlAs were used for growing high quality GaAs/AlAs layers at very low temperatures by alternately supplying Ga or Al atoms and As4 molecules to the GaAs substrate.
Abstract: When Ga or Al atoms are evaporated on a clean GaAs surface in an As-free atmosphere, they are quite mobile and migrate very rapidly along the surface even at low temperatures. This characteristic are utilized for growing high-quality GaAs and AlAs layers at very low temperatures by alternately supplying Ga or Al atoms and As4 molecules to the GaAs substrate. Applying this method, GaAs layers and AlAs–GaAs quantum well structures with reasonable photoluminescence characteristics are grown at 200°C and 300°C, respectively.

331 citations


Journal ArticleDOI
TL;DR: In this paper, the photoluminescence and photoexcitation spectra of ultrasmall structures, referred to as quantum ribbons and quantum disks, were studied and compared.
Abstract: We have studied the photoluminescence and photoexcitation spectra of ultrasmall structures, of approximately 500 A in dimension, which we refer to as quantum ribbons and quantum disks. These are fabricated from GaAs‐AlGaAs quantum wells grown by molecular beam epitaxy and patterned by electron beam lithography. Contrary to our expectation, photoluminescence from these structures is extremely efficient. The excitation spectra of the two types of small structures differ greatly from each other and from that of the as‐grown quantum wells. These differences may be a result of the confinement of the carriers in these small structures.

252 citations


Journal ArticleDOI
TL;DR: In this article, photoluminescence spectroscopy was employed to determine the temperature dependence of the interdiffusion coefficient of Al and Ga in GaAs/Al03Ga07As quantum wells.
Abstract: We have employed photoluminescence spectroscopy to determine the temperature dependence of the interdiffusion coefficient of Al and Ga in GaAs/Al03Ga07As quantum wells The position of the photoluminescence peaks, due to the n=1 electron to heavy‐hole transition, was measured before and after annealing the samples A variational calculation was employed to determine the expected position of these photoluminescence peaks and from this a value of the interdiffusion coefficient was extracted The interdiffusion process is characterized by an activation energy of about 6 eV leading to an interdiffusion coefficient at 850 °C of 4×10−19 cm2/s This technique allows for the measurement of small diffusion coefficients in a wide variety of material systems

226 citations


Journal ArticleDOI
TL;DR: In this article, the photoluminescence (PL) linewidths at 2 K were the narrowest that have been ever reported for Ga0.47In0.53As quantum wells grown by any technique.
Abstract: We have prepared by chemical beam epitaxy extremely high quality Ga0.47In0.53As/InP quantum wells with thickness as thin as 6 A. Emission as short as 1.09 μm at 2 K (1.14 μm at 300 K) was obtained. Very sharp intense efficient luminescence peaks due to excitonic transitions were obtained from all quantum wells. The photoluminescence (PL) linewidths at 2 K were the narrowest that have been ever reported for Ga0.47In0.53As quantum wells grown by any technique. In fact, these Ga0.47In0.53As quantum well linewidths are at least equal to the narrowest linewidths ever reported for the perfected GaAs/AlAs and GaAs/AlxGa1−xAs quantum wells. These linewidths indicate the ‘‘effective’’ interface roughness to be 0.12 lattice constant, which can be interpreted as that the quantum well was largely consisting of a big domain of the same thickness Lz perforated with a small fraction of small domains of (Lz+a0/2), where a0 (=5.86 A) is the lattice constant. No broadening due to band filling from impurities was found. All...

148 citations


Journal ArticleDOI
TL;DR: In this article, an intentionally doped gallium antimonide has been grown by molecular beam epitaxy on gallium arsenide and gallium anti-antimonide, and a strong correlation has been found between the quality of the layers and the degree of excess antimony flux; the best material was obtained with the minimum antimony stable growth at a particular substrate temperature.
Abstract: Unintentionally doped gallium antimonide has been grown by molecular‐beam epitaxy on gallium arsenide and gallium antimonide. Substrate temperatures in the range 480 to 620 °C and antimony to gallium flux ratios from 0.65 : 1 to 6.5 : 1 have been investigated. The deposition conditions have been related to growth morphology and to the electrical and optical properties of the epitaxial films. A strong correlation has been found between the quality of the layers and the degree of excess antimony flux; the best material in terms of both optical and electrical properties was obtained with the minimum antimony stable growth at a particular substrate temperature. All the material exhibited residual p‐type behavior. The lowest hole concentration achieved was 7.8×1015 cm−3 with a corresponding room‐temperature mobility of 950 cm2/V s. The narrowest PL (photoluminescence) features observed were peaks associated with bound exciton transitions with half‐widths of 2–3 meV.

145 citations


Journal ArticleDOI
TL;DR: The carrier localization and the inhibition of carrier transport along the growth axis (vertical transport) are studied by means of photoluminescence experiments performed at 1.7 K in purposely disordered GaAs/GaAlAs superlattices.
Abstract: The carrier localization and the inhibition of carrier transport along the growth axis (vertical transport) are studied by means of photoluminescence experiments performed at 1.7 K in purposely disordered GaAs/GaAlAs superlattices. When the well widths are randomly varied, minibands of extended states shrink and localized states are created in their tails. Consequently the vertical transport efficiency decreases and sharply vanishes when disorder induces fluctuations of the eigenenergies which are comparable to half of the unperturbed superlattice bandwidth. By an increase of temperature the vertical transport becomes thermally activated.

144 citations


Journal ArticleDOI
TL;DR: In this paper, a detailed study of the optical properties of InGaAs-InP single quantum wells (QWS) grown by atmospheric-pressure metal-organic chemical vapour deposition is described.
Abstract: A detailed study of the optical properties of InGaAs-InP single quantum wells (QWS) grown by atmospheric-pressure metal-organic chemical vapour deposition is described. Photoluminescence (PL), photoluminescence excitation (PLE), photoconductivity (PC) and electroreflectance (ER) are employed to study both undoped and modulation-doped quantum wells. The role of extrinsic processes in determining the low-temperature PL spectra is demonstrated from the variation of peak position and linewidth with temperature. The best PL linewidth obtained for a 150 AA well is 5.3 meV, fairly close to the limit imposed by alloy fluctuations in the InGaAs. The role of free carriers in the undoped QWS in determining the energy threshold for optical absorption is demonstrated from a comparison of PLE and PC spectra. Lineshape fitting of the PL spectra is described, and it is deduced that at 160K recombination processes in both doped and undoped QWS proceed with wavevector conservation, although at lower temperatures highly anomalous lineshapes are found in modulation-doped samples. The observation of a threshold in PC spectra under forward bias is interpreted as a transition from the valence-band well to the top of the conduction well. The ratio of the conduction- to valence-band discontinuities is deduced to be approximately 0.4:0.6.

135 citations


Journal ArticleDOI
TL;DR: In this paper, a long-lived emission at low temperatures in AlAs/GaAs superlattices with approximately equal thicknesses of AlAs and GaAs and with periods in the range 18-60 A. The exciton is found to be at the zone boundary, and to consist of a Γ hole localized in the GaAs, and an AlAs X-point electron.
Abstract: We have found a long‐lived emission at low temperatures in AlAs/GaAs superlattices with approximately equal thicknesses of AlAs and GaAs and with periods in the range 18–60 A. The emission shows the nonexponential time decay characteristic of an indirect exciton made allowed by disorder. The exciton is found to be at the zone boundary, and to consist of a Γ hole localized in the GaAs and an AlAs X‐point electron. The disorder is at the AlAs‐GaAs interfaces. There is no ‘‘camel’s back’’ in the exciton dispersion.

Journal ArticleDOI
TL;DR: In this paper, the photoluminescence spectra of GaAs quantum wells of widths 26 to 150 A\r{} were studied as a function of hydrostatic pressure (0--70 kbar) at 80 and 150 K.
Abstract: Photoluminescence spectra of GaAs quantum wells of widths 26 to 150 A\r{} are studied as a function of hydrostatic pressure (0--70 kbar) at 80 and 150 K. The pressure coefficients of both the heavy- and light-hole excitons are found to decrease with decreasing well width. The direct to indirect conduction-band crossover, leading to the formation of type-II heterostructures, occurs at higher pressures for wider wells. A transition associated with the X conduction band in quantum-well structures is observed and its pressure dependence is established. Correlating this transition to barrier-to-well recombination determines the valence-band offset.

Journal ArticleDOI
TL;DR: In this article, the pressure dependence of quantum-well bound states formed in the GaAs/AlxGa1−xAs heterostructure system was investigated using photoluminescence (8 K) and in full-scale pseudopotential calculation.
Abstract: We report experiment and theory on the pressure dependence of quantum‐well bound states formed in the GaAs/AlxGa1−xAs heterostructure system. Using MQW’s and SL’s of various barrier compositions x, we trace in photoluminescence (8 K), and in full‐scale pseudopotential calculation, the pressure‐induced evolution of the lowest spatially confined states within the wells. With increasing pressure Γ‐confined states follow the shift to higher energies of the direct GaAs band gap. At critical pressures a crossing occurs between these Γ bound states and the barrier indirect X states. Here, Γ intensities plunge and new emission tracking the X edges appears. Confirmed in wave function calculation, these new transitions occur across the heterointerface, between X‐confined electrons within the AlxGa1−xAs and Γ‐confined holes within the GaAs. Arising from valence‐offset‐induced staggered band alignment, critical pressures for observation of these states decrease with increasing Al mole fraction. We thus obtain, with p...

Journal ArticleDOI
TL;DR: In this article, a series of MBE-grown single-quantum-well structures (SQWHs) consisting of an unintentionally doped, highly strained (e∼2%) In0.28Ga0.72As quantum well sandwiched between GaAs confining layers are examined using low-temperature photoluminescence techniques.
Abstract: Strain and quantum‐size effects in pseudomorphic InxGa1−xAs–GaAs single‐quantum‐well heterostructures (SQWHs) are examined using low‐temperature photoluminescence techniques. Strain effects in InxGa1−xAs epitaxial layers are first described, then photoluminescence data for a series of MBE‐grown pseudomorphic SQWHs are presented and discussed. Each SQWH consists of an unintentionally doped, highly strained (e∼2%) In0.28Ga0.72As quantum well sandwiched between GaAs confining layers. The structures were grown consecutively under identical conditions, with quantum‐well thicknesses ranging from 17 to 430 A. The thinner quantum‐well structures exhibit luminescence characteristics indicative of high‐quality material (photoluminescence half width ∼6 meV for Lz ∼17 A), whereas significant broadening and eventual quenching of the photoluminescence peak is observed as alloy layer thicknesses approach and exceed the critical value. Quantum‐well luminescence from the thinner (Lz ≤38 A) SQWHs is dominated by a single, ...

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the photoluminescence of the rare earth element erbium implanted in GaAs, InP, and GaP through 10-K photoluminance essentially as a function of anneal temperature, time, and method.
Abstract: The characteristic 1.54‐μm emission from the rare‐earth element erbium implanted in GaAs, InP, and GaP was investigated through 10‐K photoluminescence essentially as a function of anneal temperature, time, and method. The strip‐heater, forming‐gas, and quartz‐ampoule anneal methods were utilized in the range of 400 to 1000 °C. Erbium‐related emissions were observed from 1.48 to 1.64 μm and were observable at emission temperatures of up to 260 K for InP:Er and 296 K for GaP:Er and GaAs:Er. Out of the three semiconductors, GaAs:Er was observed to exhibit the highest optical activation using a square‐profile implantation technique. Dependent on the anneal method, optimum Er emissions occurred between 650 and 800 °C for GaAs, for InP between 575 and 625 °C, and for GaP between 800 and 950 °C. In general, the forming‐gas anneal method proved most successful; however, maximum luminescence including sharper emission lines was achieved through the strip‐heater method. This method, with an anneal time of 10 s, sho...

Journal ArticleDOI
TL;DR: In this article, the photoluminescence of GaAs/Si grown by OMCVD has been analyzed as a function of temperature and the dominant high temperature line identified as a conduction-band-to-valence-band transition.

Journal ArticleDOI
TL;DR: In this paper, a comparison of the luminescence of GaAlAs/GaAs/GAAlAs quantum wells (QW) grown by molecular beam epitaxy with and without a 1-100 s interruption of the growth at the interfaces is presented.
Abstract: A comparison of the luminescence of GaAlAs/GaAs/GaAlAs quantum wells (QW) grown by molecular beam epitaxy with and without a 1–100 s interruption of the growth at the interfaces is presented. Well widths of 2 and 5 nm are studied as model systems. The luminescence from the noninterrupted samples consists of Gaussian shaped doublets. A line shape theory is outlined, allowing for the first time a determination of the distribution of the microscopic chemical and crystallographic disorder of the interfaces from the spectra. All samples were grown under nominally identical conditions and all show the same Gaussian distribution of the interface position. The full width at half maximum of the distribution function is 1.25 A. The interfaces in these samples are believed to have an island‐like character with a typical island size of much less than 17 nm. Interruption of the growth by a few seconds changes the luminescence line shape function qualitatively. The spectrum splits into doublets, with doublet fine struc...

Journal ArticleDOI
TL;DR: Etude par la methode de melange de quatre ondes a resolution temporelle realisee sur couches optiquement minces dans des conditions assurant une contribution negligeable de l'interaction exciton-exciton.
Abstract: The phase coherence and orientational relaxation of excitons resonantly excited in optically thin GaAs layers by a picosecond light pulse is explored by means of time-resolved degenerate-four-wave mixing. At low excitation intensities where contributions due to exciton-exciton scattering can be neglected, a rapid loss of the phase coherence as well as of the optical alignment of the excitonic dipoles within 7 ps is observed. This implies a weak coherent coupling between excitons and photons and raises the question about the range of validity of the commonly employed polariton concept for GaAs.

Journal ArticleDOI
TL;DR: The effect of hydrogen plasma exposure on the deep level defects present in GaAs grown by molecular beam epitaxy (MBE) has been investigated by deep level transient spectroscopy and by photoluminescence as discussed by the authors.
Abstract: The effect of hydrogen plasma exposure on the deep level defects present in GaAs grown by molecular beam epitaxy (MBE) has been investigated by deep level transient spectroscopy and by photoluminescence. The three commonly observed defects in MBE grown layers, the M1, M2, and M4 levels, found to be present at a total concentration of 5×1013 cm−3, are completely passivated by exposure to the hydrogen plasma. At low carrier concentration, in samples where surface recombination is suppressed by a thin GaxAl1−xAs cap, passivation of these defects increases photoluminescence efficiency by factors of 30 and 100 at 298 and 77 K, respectively. Defect passivation occurs in addition to the previously reported donor neutralization, but, whereas the latter is removed by a 400 °C, 5 min anneal, the former remains fully effective. Only upon 600 °C, 5 min annealing does the defect level passivation begin to be lost. Thus there is a wide temperature window within which it is possible to regain the carrier concentration without loss of passivation of the deep level defects.

Journal ArticleDOI
TL;DR: Analyse du spectre de luminescence a 4,8 K, d'un monocristal a tres faible concentration de chrome as mentioned in this paper, a 4.8 K.

Journal ArticleDOI
TL;DR: In this article, single quantum wells of GaInAs and GaAsP isolated by 150-A-thick InP barriers have been grown by gas source molecular beam epitaxy and photoluminescence and transmission electron microscopy were used to characterize them.
Abstract: Single quantum wells of GaInAs and GaInAsP isolated by 150‐A‐thick InP barriers have been grown by gas source molecular beam epitaxy. The quantum wells ranged in thickness from 5 to 30 A. Photoluminescence and transmission electron microscopy were used to characterize them. Intense luminescence was observed at low temperature even from the thinnest of the wells. The spectral shifts due to the quantum size effect were 450 meV for the quaternary 5‐A well and 534 meV for the ternary 5‐A well. The latter constitutes approximately 85% of the total band‐gap discontinuity. The emission linewidths suggest that on a scale larger than the exciton diameter the interface fluctuates less than one monolayer.

Journal ArticleDOI
TL;DR: In this article, a detailed review of the recent work involving quantum well structures in the (Zn, Mn)Se system, with the second part emphasizing (Cd, Mn), is presented.
Abstract: At this time, there is evident a sharp increase of interest in the II-VI class of semiconducting compounds largely due to recent success in the growth of these materials by molecular beam epitaxy (MBE). One of the more important areas for application of high-quality II-VI films is infrared imaging where CdTe deposited by MBE onto GaAs substrates is proposed as the substrate for subsequent HgCdTe and HgTe/CdTe superlattice deposition. Moreover, interest in the wide-gap II-VI compounds is stimulated by the need for electronically addressable flat panel display devices, and for the development of wide-gap (blue) LED and injection laser devices. For applications in the blue portion of the visible spectrum, ZnSe and ZnS have long been favored candidates. Very high quality ZnSe has recently been grown by MBE. The photoluminescence spectra of the MBE-grown ZnSe samples grown at Purdue University and elsewhere strongly suggests that, in many cases, the film quality exceeds that obtainable in bulk form. In addition to the Conventional II-VI materials, a new class of materials called diluted magnetic semiconductors (DMS) are currently receiving considerable attention. DMS are II-VI semiconductors such as CdTe or ZnSe with a fraction of the group II element substituted by a magnetic transition element such as Mn. The incorporation of Mn leads to very large magnetooptic effects, on the Order of several hundred times that exhibited by conventional semiconductors of a comparable bandgap. An especially significant feature of II-VI DMS materials is the increase in bandgap resulting from Mn incorporation. The band-gap increases with Mn mole fraction in a manner similar to the effect of Al in the (Ga, Al)As system, and with similar implications to the creation of quantum well structures and superlattices. The first part of this paper reviews our recent work involving quantum well structures in the (Zn, Mn)Se system, with the second part emphasizing (Cd, Mn)Te. Included in the discussion of superlattice structures in (Cd, Mn)Te is a description of recent results concerning the heteroepitaxial growth of CdTe on GaAs-materials having a lattice constant mismatch of 14.6 percent.

Journal ArticleDOI
TL;DR: In this paper, the complex dielectric function was deduced for the energy range 1.8-5.6 eV for the as-grown as well as for thermally annealed carbon films.
Abstract: Plasma‐deposited hard amorphous carbon films were studied by ellipsometry and photoluminescence. Both techniques are suited for the optical characterization of films on transparent as well as on opaque substrates. From the ellipsometric data the complex dielectric function was deduced for the energy range 1.8–5.6 eV for the as‐grown as well as for thermally annealed films. In the photoluminescence spectrum both peak energy and emission intensity were found to increase (the latter by four orders of magnitude) when going from hard, strongly cross‐linked films to softer, polymerlike layers.

Journal ArticleDOI
TL;DR: In this article, the origin of a nonradiative center in AlGaAs grown by molecular beam epitaxy was investigated by secondary ion mass spectroscopy and deep level transient spectrograms.
Abstract: Origin of a nonradiative center in AlGaAs grown by molecular‐beam epitaxy was investigated by secondary ion mass spectroscopy and deep‐level transient spectroscopy, from the change of photoluminescence intensity with anneal treatment, and from its comparison with GaAs. Aluminum‐oxygen complex is a most probable defect which acts as a nonradiative center in AlGaAs, and the oxygen would evaporate as Al2O from the surface, which would be a reason why the photoluminescence intensity increases under higher substrate temperature and lower V/III flux ratio. The electron‐trap level at 0.76 eV from the conduction band would be the recombination center, and the photoluminescence intensity is inversely proportional to the trap concentration.

Journal ArticleDOI
TL;DR: In this article, low temperature photoluminescence (PL) in the energy range 1.61 eV to 140 eV was reported for three different energy regions and observed for substrate temperatures from 170°C to 285°C.

Journal ArticleDOI
TL;DR: In this article, the intensity of visible emission in infrared to visible multiphoton Y1−xErxF3 upconversion phosphors pumped with 1.5μm radiation from InGaAsP-laser sources was observed.
Abstract: Intense visible emission in the red, green, and blue has been observed from infrared to visible multiphoton Y1−xErxF3 upconversion phosphors pumped with 1.5‐μm radiation from InGaAsP‐laser sources. With 0.01


Journal ArticleDOI
TL;DR: In this paper, the optical spectroscopy of nickel-doped LiGa 5 O 8 is presented, and it is shown that the dopant nickel ion is doubly charged and occupies a site of near-octahedral symmetry.

Journal ArticleDOI
TL;DR: In this paper, the photoexcitation of solitons, polarons, and bipolarons leads to relatively large third-order nonlinear optical processes (χ (3) ) on time scales of order 10 −13 s.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the time-resolved and excitation-dependent photoluminescence of GaAs/Al x Ga 1-x As quantum well structures and showed that recombination takes place between free carriers, not excitons, at room temperature for carrier densities at and above the mid -1016cm-3level.
Abstract: Time-resolved and excitation-dependent photoluminescence of GaAs/Al x Ga 1-x As quantum well structures reveal that recombination takes place between free carriers, not excitons, at room temperature for carrier densities at and above the mid -1016cm-3level. Other samples show trapping and release of carriers from traps, evidence of dynamic Shockley, Hall, and Read recombination for optically active traps. The traps can be saturated to a large extent. Further studies show that they are associated with interfaces between different materials and that they become active at a temperature around 150 K. Results from all samples indicate that the bimolecular radiative recombination coefficient B for quantum wells is no larger than the value of B for bulk GaAs, and may in fact be smaller. This is one of the first studies of time-resolved luminescence of impurities in quantum well structures. Impurity decays at low temperatures are found to be quite slow. A spectral line which appeared to be longitudinal optical phonon-shifted emission is shown to be due to an acceptor impurity.