Showing papers on "Photoluminescence published in 1987"
TL;DR: The fundamental relationship between radiative lifetime and spectral linewidth of freeexcitons is demonstrated theoretically and experimentally for quasi 2D excitons in GaAs/AlGaAs quantum wells.
Abstract: The fundamental relationship between radiative lifetime and spectral linewidth of free excitons is demonstrated theoretically and experimentally for quasi 2D excitons in GaAs/AlGaAs quantum wells.
820 citations
TL;DR: In this article, the optical properties of glasses containing a small amount of thermally developed CdSexS1−x microcrystalline phase are studied with emphasis on quantum confinement effects exhibited at small crystallite size.
Abstract: The optical properties of glasses containing a small amount of thermally developed CdSexS1−x microcrystalline phase are studied with emphasis on quantum confinement effects exhibited at small crystallite size. Optical absorption, photoluminescence, x‐ray diffraction, and transmission electron microscopy are used to examine microcrystallites as a function of composition and development. Results are presented for a series of commercially available CorningR filter glasses with a selenium mole fraction in the range 0.28≤x≤0.74, as well as for several experimental glasses in which the average microcrystallite diameters range from 30 to 80 A. Optical effects observed in the experimental glasses that are due to electron and hole confinement are not present in the filter glasses considered; variations in optical properties of the filters are due to changes in stoichiometry of the CdSexS1−x mixed anion system. A brief discussion of other microcrystalline phases in glass is also presented. These microcrystallites show room‐temperature optical absorption structure analogous to bulk crystal excitons; the temperature dependence of this structure is contrasted with that resulting from quantum confinement in CdSexS1−x glasses.
564 citations
TL;DR: In this article, the band-gap energy (Eg) of metalorganic vapor phase epitaxially (MOVPE) grown Ga 0.5In0.5P lattice matched to (001) GaAs is presented as a function of a wide range of V/III ratios and growth temperatures.
Abstract: The band‐gap energy (Eg) of metalorganic vapor phase epitaxially (MOVPE) grown Ga0.5In0.5P lattice matched to (001) GaAs is presented as a function of a wide range of V/III ratios and growth temperatures. Photoluminescence, Raman scattering spectroscopy, transmission electron microscopy, and impurity diffusion were used to investigate this functional relationship. Two pieces of evidence are shown which demonstrate that MOVPE Ga0.5In0.5P epitaxial layers with ‘‘abnormal’’ Eg∼1.85 eV and ‘‘normal’’ Eg∼1.9 eV correspond to an ordered and a random (Ga,In) distribution on column III sublattices, respectively. In an ordered state, a sequence of (110) planes...GaGaInInGaGaInIn...in the [110] direction is the most probable distribution.
363 citations
TL;DR: InGaAs/InP quantum well layers grown by gas source molecular beam epitaxy have been used to fabricate quantum wires and boxes with transverse dimensions as small as ∼300 A.
Abstract: InGaAs/InP quantum well layers grown by gas source molecular beam epitaxy have been used to fabricate quantum wires and boxes with transverse dimensions as small as ∼300 A. These artificial structures exhibit intense low‐temperature photoluminescence and show exciton shifts of 8–14 meV expected of low dimensional confinement. Low surface recombination velocity characteristic of InP and its alloys should allow luminescence studies of features as small as ∼30 A under moderate excitation intensities.
280 citations
TL;DR: In this paper, the critical width for misfit dislocation generation was determined for molecular beam epitaxy grown strained InxGa1−xAs (0.1
Abstract: The critical width Lc for misfit dislocation generation has been determined for molecular beam epitaxy grown strained InxGa1−xAs (0.1
226 citations
TL;DR: In this paper, the passivating effects of spincoated films of Na2S⋅9H2O on GaAs surfaces have been studied using roomtemperature photoluminescence (PL) and low-temperature PL spectroscopy.
Abstract: The passivating effects of spin‐coated films of Na2S⋅9H2O on GaAs surfaces have been studied using room‐temperature photoluminescence (PL) and low‐temperature PL spectroscopy. After passivation, the 300 K PL efficiency is increased on both n‐ and p‐type material; improvements of up to 2800× are observed. The surface field and surface recombination‐related notch features in the free and bound exciton emission spectra at low temperature are eliminated, implying that the residual band bending under illumination is less than 0.15 V.
209 citations
TL;DR: In this article, the photoluminescence of nominally undoped quantum wells is studied as a function of temperature and excitation power, and the role of an excitonic process in 4K radiative recombinations is pointed out.
Abstract: The properties of InGaAs‐InP single quantum wells have been studied by using the photoluminescence technique. Samples were grown by atmospheric pressure metalorganic vapor phase epitaxy. The photoluminescence of nominally undoped quantum wells is studied as a function of temperature and excitation power. The role of an excitonic process in 4‐K radiative recombinations is pointed out. The best linewidth obtained for a 140‐A well is 4.5 meV, fairly close to the limit imposed by alloy fluctuations in the InGaAs thick layers. Radiative recombination is more and more efficient with decreasing well thickness and higher than in InGaAs bulk material.
190 citations
TL;DR: In this paper, the critical thickness hc of strained InxGa1−xAs layers grown by molecular beam epitaxy on GaAs(100) substrates was determined by double-crystal x-ray diffraction for 0.07≤x≤0.25.
Abstract: The critical thickness hc of strained InxGa1−xAs layers grown by molecular beam epitaxy on GaAs(100) substrates is determined by double‐crystal x‐ray diffraction for 0.07≤x≤0.25. The experimental results are in good agreement with critical thicknesses calculated from the energy balance model of R. People and J. C. Bean [Appl. Phys. Lett. 47, 322 (1985)] but differ from prior photoluminescence measurements of hc for this material. Beyond the critical thickness the transition from the strained to the relaxed state occurs more rapidly as the In concentration and hence the lattice mismatch increases.
176 citations
TL;DR: Time-resolved measurements of photoluminescence in bulk a-${\mathrm{SiO}}_{2}$ using 7.9- and 6.4-eV excitation are reported, and there is a very broad luminescence peaking between 3\char21{}4 eV but extending to below the 1.5- eV cutoff of the measurements.
Abstract: We report time-resolved measurements of photoluminescence in bulk a-${\mathrm{SiO}}_{2}$ using 7.9- and 6.4-eV excitation. Time-resolved spectra have been obtained at room temperature and 25 K, and the intensity and decay rates of various luminescence bands have been measured as a function of temperature. Bands at 1.9, 2.2, 2.7, and 4.3 eV are identified. In addition, there is a very broad luminescence peaking between 3\char21{}4 eV but extending to below the 1.5-eV cutoff of our measurements. We have also measured photoluminescence in crystalline quartz and in a thermally grown oxide. Both the 4.3- and 1.9-eV bands are seen in the thermal oxide, but the 2.7-eV band is absent. In the crystal, the 1.9-eV band is absent.
167 citations
TL;DR: In this article, high-quality n-type ZnSe layers have been grown by molecular beam epitaxy using chlorine (Cl) as a dopant, showing mirrorlike morphology and good crystallinity, although some degrade in crystallinity is observed at a heavy doping.
Abstract: High‐quality n‐type ZnSe layers have been grown by molecular‐beam epitaxy using chlorine (Cl) as a dopant. The Cl‐doped ZnSe layers showed mirrorlike morphology and good crystallinity, although some degrade in crystallinity is observed at a heavy doping. The carrier concentration of the layer could be widely controlled by a ZnCl2 Knudsen cell temperature. The carrier concentration attained 1×1019 cm−3, where the resistivity was as low as 3×10−3 Ω cm, indicating a remarkable improvement compared to the previous work using group‐III elements as a dopant. Hall mobilities at room temperature were in the range of 200–400 cm2/(V s), depending on the doping level. The Cl‐doped ZnSe layer exhibited strong blue near‐band‐gap photoluminescence (PL) with suppressed deep‐level emission at room temperature. The 4.2‐K PL of the layer was dominated by strong emission of excitons bound to neutral donors originating from substitutional Cl atoms. It was found by a secondary ion‐mass‐spectroscopy analysis that diffusion of ...
151 citations
TL;DR: In this paper, a model of hetero-interface structures of GaAs-AlxGa1−xAs quantum wells (QWs) is presented, where top (AlGaAs-on-GaAs) interfaces formed by continuous MBE have the roughness of one atomic layer height whose atomic step interval is 200 A, resulting in a well-known photoluminescence broadening from QWs.
TL;DR: In this article, the interband optical absorption of a nonuniform semiconductor quantum dot system is calculated and the effect of dot size variation on the resolvability of the absorption peaks is estimated.
Abstract: The interband optical absorption of a nonuniform semiconductor quantum dot system is calculated. The effect of dot size variation on the resolvability of the absorption peaks is estimated. The dots are assumed to be cubic, with a size distribution described by a Gaussian function. It is shown that the total absorption spectrum of such a dot system depends strongly on the dot size distribution described by the parameter ξ, the ratio of the standard deviation of the dot size to the average dot size of the system. The range of ξ values for which the absorption peaks are resolvable is given.
TL;DR: In this article, the effect of lattice deformation on optical properties and lattice parameters of ZnSe thin films, whose thickness ranges from 0.05 to 22 μm, grown by either atomic layer epitaxy or molecular beam epitaxy on (100)GaAs substrates, has been investigated.
TL;DR: In this paper, the critical layer thickness (CLT) for single strained-layer epitaxy in the InGaAs/GaAs system was determined by two sensitive techniques: Hall-effect measurements at 77 K and photoluminescence microscopy.
Abstract: We report accurate determination of the critical layer thickness (CLT) for single strained‐layer epitaxy in the InGaAs/GaAs system. Our samples were molecular beam epitaxially grown, selectively doped, single quantum well structures comprising a strained In0.2Ga0.8As layer imbedded in GaAs. We determined the CLT by two sensitive techniques: Hall‐effect measurements at 77 K and photoluminescence microscopy. Both techniques indicate a CLT of about 20 nm. This value is close to that determined previously (∼15 nm) for comparable strained‐layer superlattices, but considerably less than the value of ∼45 nm suggested by recent x‐ray rocking‐curve measurements. We show by a simple calculation that photoluminescence microscopy is more than two orders of magnitude more sensitive to dislocations than x‐ray diffraction. Our results re‐emphasize the necessity of using high‐sensitivity techniques for accurate determination of critical layer thicknesses.
TL;DR: Using a color center laser, photoluminescence excitation measurements were performed on GaAs:Er grown by molecular beam epitaxy as mentioned in this paper, which showed that only one type of Er3+ center is responsible for the sharply structured emission band at 1.54 μm.
Abstract: Using a tunable color center laser, photoluminescence excitation measurements were performed on GaAs:Er grown by molecular‐beam epitaxy. These measurements show that only one type of Er3+ center is responsible for the sharply structured emission band at 1.54 μm. The multiplicity of the zero‐phonon lines indicates that this Er3+ center has lower than cubic symmetry and that the luminescence arises from the intracenter transition 4I13/2→4I15/2 of Er3+ (4f 11).
TL;DR: In this paper, the results of OMVPE growth of GaAs using trimethylgallium (TMGa) and tertiarybutylarsine (TBAs) in a one atmosphere ambient were reported.
Abstract: The use of AsH3 in the organometallic vapor phase epitaxial (OMVPE) growth of GaAs and other As containing III/V semiconductors has a number of disadvantages, including toxicity hazard, purity problems associated with storage cylinders, and low pyrolysis rate at the low temperatures often desirable in OMVPE growth. A new organometallic source, tertiarybutylarsine (TBAs), has recently become available. In this letter we report the results of OMVPE growth of GaAs using trimethylgallium (TMGa) and TBAs in a one atmosphere ambient. The major results of the study are (1) the vapor pressure of TBAs is measured to be 96 Torr at 10 °C, (2) the pyrolysis rate of TBAs appears to be greater than that of AsH3 under similar conditions, (3) as a consequence of (2), excellent morphology GaAs layers can be grown at lower values of V/III ratio (approximately unity) using TBAs than using AsH3 (4) no additional carbon incorporation is produced by the use of the organometallic group V source. These factors make TBAs a promis...
TL;DR: In this paper, the absolute determination of the Al concentration, x, in epitaxial layers of AlxGa1−xAs was carried out using a nuclear reaction technique, which utilizes the narrow resonances found in the 27Al(p,γ)Si28 reaction, together with Rutherford backscattering measurements, to obtain accurate values of the alloy composition.
Abstract: The absolute determination of the Al concentration, x, in epitaxial layers of AlxGa1−xAs was carried out using a nuclear reaction technique. This technique utilizes the narrow resonances found in the 27Al( p,γ)Si28 reaction, together with Rutherford backscattering measurements, to obtain accurate values of the alloy composition. The AlxGa1−xAs band edge was measured on these samples through low‐temperature photoluminescence (2 K) measurements. An improved value of the direct edge (Γ) on composition was determined to be EΓg =1.512 +1.455x(eV) within a ±0.3% limit. The direct‐to‐indirect transition was found to occur at an Al concentration of x≂0.37±0.015, lower than previously reported for He temperatures.
TL;DR: In this paper, the authors report the operation of a new surface emitting laser, which is fabricated with molecular beam epitaxy by the growth of quarter-wave high reflectors of AlAs/Al0.4Ga0.6As (710 A/630 A).
Abstract: We report operation of a new surface‐emitting laser. This epitaxial laser is fabricated with molecular beam epitaxy by the growth of quarter‐wave high reflectors of AlAs/Al0.4Ga0.6As (710 A/630 A) which surround a 4.5‐μm‐thick multiple quantum well of GaAs/Al0.4Ga0.6As (100 A/200 A). We characterize the structure with cw spectroscopy (absorption, reflection, and luminescence) and investigate stimulated emission spectra under pulsed photopumping. When photopumped, the structure lases in its as‐grown condition without need of substrate removal, cleaving, or heatsinking. The lasing wavelength is as short as 7400 A and can be tuned to as long as 8400 A by positioning the pump spot to different regions across the wafer. The pulsed threshold irradiance has a very weak temperature dependence varying from 6×105 W/cm2 at 4.2 K to 1.6×106 W/cm2 at 295 K.
TL;DR: Very high quality GaAs/Al 0.37 Ga 0.63 as mentioned in this paper were obtained for single quantum wells with extended monolayer-flat regions by molecular beam epitaxy with growth interruption at hetero-interfaces.
TL;DR: In this paper, electron spin resonance measurements and spectroscopic data on the doped poly(3-hexylthienylene) macromolecules in solution were used to determine the nature of the charge storage configurations.
TL;DR: In this paper, the radiative recombination coefficient of two-dimensional free carriers, N and P, in a selectively doped GaAs/n−Al 0.3Ga0.7As quantum well was determined in the temperature range T between 15 and 300 K by measuring the decay time τ of photoluminescence from the quantum well with electron density N0=1×1012/cm2.
Abstract: The radiative recombination coefficient B, defined by dN/dt=dP/dt≡−BNP, of two‐dimensional free carriers, N and P, in a selectively doped GaAs/n‐Al0.3Ga0.7As quantum well was determined in the temperature range T between 15 and 300 K by measuring the decay time τ of photoluminescence from the quantum well with electron density N0=1×1012/cm2. It is found that B(=1/τN0) is 1.1–1.9×10−4 cm2/s at 300 K and increases as T is lowered, reaching 2.3×10−3 cm2/s (τ∼0.43 ns) at 15 K. The initial increase of B is nearly proportional to 1/T, whereas B tends to saturate at low temperature. These experimental findings are shown to be well explained by the theory of band‐to‐band recombination of two‐dimensional carriers in quantum wells.
TL;DR: In this paper, the optical determination of exciton binding energies in small-period GaAs/Ga0.7Al0.3As superlattices was performed by means of low-temperature photoluminescence excitation spectroscopy.
Abstract: We report the optical determination of exciton binding energies in small-period GaAs/Ga0.7Al0.3As superlattices by means of low-temperature photoluminescence excitation spectroscopy and photoluminescence spectroscopy as a function of temperature. The heavy-hole exciton binding energy decreases with decreasing superlattice period. Our experimental findings are in reasonable agreement with a variational calculation.
TL;DR: In this article, the authors studied six GaAs/AlAs superlattices with periods ranging from 18 to 60 A and different average aluminum composition and found that the lowest energy transitions arise from an exciton involving a heavy hole state mostly confined in the GaAs layer and at the Brillouin zone center (Λ), and an electronic state of X character confined in AlAs layers.
TL;DR: In this paper, the Frohlich electron-photon interaction and the Lyddane-Sachs-Teller (LST) splittings of the optic phonon modes in mixed crystals with two-mode behavior were discussed.
Abstract: The authors discuss the Frohlich electron-photon interaction and the Lyddane-Sachs-Teller (LST) splittings of the optic phonon modes in mixed crystals with 'two-mode' behaviour. The theoretical results for these properties within a two-mode model are described. For the alloy In0.53Ga0.47As they discuss the experimental evidence for the LST splittings and the electron-phonon coupling of the two longitudinal optic (LO) phonon branches, including their own studies of phonon satellites of exciton recombination in In0.53Ga0.47As/InP quantum wells. The electron-phonon coupling is much weaker for the 'InAs-like' modes than for the 'GaAs-like' modes. They show that the primary reason for this effect is coupling of the LO distortions of the alloy by the macroscopic electric field.
TL;DR: The doping of molecular beam epitaxial GaAs with erbium up to a concentration of 2×1019 cm−3 has been successfully demonstrated in this article, where photoluminescence from a rare earth element incorporated in a III-V semiconductor has been observed at room temperature.
Abstract: The doping of molecular beam epitaxial GaAs with erbium up to a concentration of 2×1019 cm−3 has been successfully demonstrated. Up to a concentration of about 5×1018 cm−3 the surface morphology remained good but for higher doping levels the surface became structured. Hall and profile measurements indicate that erbium doping gives rise to a trapping level capable of compensating silicon‐doped layers. For the first time photoluminescence from a rare earth element incorporated in a III‐V semiconductor has been observed at room temperature.
TL;DR: In this paper, the spectral properties of AlxGa1−xAs/GaAs coupled quantum well structures were investigated under the Stark perturbation, and it was shown that positive energy shifts and high sensitivity to electric fields have been interpreted as evidence of well coupling.
Abstract: Optical spectra near the band edges of AlxGa1−xAs/GaAs coupled quantum well structures are found to exhibit rich structure. Under the Stark perturbation, these transitions have behavior remarkably different from those associated with single quantum wells. Positive energy shifts and high sensitivity to electric fields have been observed and interpreted as evidence of well coupling. Results of a simple numerical calculation support this interpretation.
TL;DR: In this paper, the compositional dependence of the direct gap was found to be EΓ(x)=1.35+1.83x+0.38x2 (eV).
Abstract: AlxIn1−xP epilayers grown by organometallic vapor phase epitaxy are characterized by electroreflectance, photoluminescence, and Raman spectroscopy. Electroreflectance measurements of the E0 band gap show significant bowing of the direct band gap with composition. The compositional dependence of the direct gap is found to be EΓ(x)=1.35+1.83x+0.38x2 (eV). In the Raman scattering spectrum, the AlP‐like longitudinal optical phonon mode is identified and its energy is measured as a function of composition.
TL;DR: In this paper, an improved time-resolved luminescence spectroscopy system using sum frequency generation was reported, which has the following attributes: high time resolution (<400 fs, currently limited by the laser), ability to determine absolute zero in time delay with high precision, wide spectral range, and large dynamic range.
Abstract: We report an improved time‐resolved luminescence spectroscopy system using sum frequency generation. The system has the following attributes: high time resolution (<400 fs, currently limited by the laser), ability to determine absolute zero in time delay with high precision, wide spectral range, and large dynamic range which allows measurement of luminescence under weak photoexcitation. We illustrate these with examples of time‐resolved luminescence spectra from GaAs.
TL;DR: In this article, a comparison between the quenching processes of rare earth ion luminescence in molecular and non-molecular solids is made, and the results obtained in this field for both types of solids are compared in order to improve the mutual interaction.
TL;DR: In this paper, the Fourier transform photoluminescence spectroscopy (FTPS) was used to measure boron, phosphorus and aluminium concentrations in silicon by comparing the intensities of bound and free-exciton luminescence features.
Abstract: Calibrations are reported for measuring boron, phosphorus and aluminium concentrations in silicon by comparing the intensities of bound-exciton and free-exciton luminescence features. Particular attention has been directed towards investigating the effects of excitation density and instrumental resolution. The luminescence spectra have been corrected for the system response so that the calibrations are independent of the equipment used and are hence transferable. Fourier transform rather than dispersive spectroscopy has been employed to measure the luminescence spectra. Since Fourier transform photoluminescence spectroscopy is a relatively new technique, it is described in some detail.