Showing papers on "Photoluminescence published in 1973"

Polariton Reflectance and Photoluminescence in High-Purity GaAs

Abstract: The low-temperature optical reflectance and photoluminescence of high-purity GaAs have been studied in the spectral energy region near the direct fundamental gap. Strong free-exciton reflectance structure is seen. This structure is strongly influenced by both spatial dispersion and polariton effects. The general shape and strength of this reflectance structure are well accounted for by polariton theory with the unknown surface-barrier thickness as the only adjustable parameter. The sharp spike in the reflectance data provides an accurate value ${E}_{L}=1.51515\ifmmode\pm\else\textpm\fi{}0.00015$ eV for the longitudinal exciton energy at 2 K. The longitudinal-transverse exciton splitting falls within the range 0.1-0.25 meV. Two structures in the luminescence spectrum are interpreted, respectively, as lower (LPB) and upper polariton branch (UPB) luminescence. The LPB luminescence occurs at the transverse exciton energy as expected. The UPB luminescence, previously identified as the "free-exciton" structure, has the rather unusual behavior that it always occurs above, and has its low-energy "onset" at, the longitudinal exciton energy. Uniaxial stress and temperature-dependence results are presented to support the interpretation of the data. The over-all energy splittings and polarization behavior seen in both reflectance and luminescence spectra agree with theoretical results. The stress behavior of the reflectance provides the value $j=\ensuremath{-}0.05\ifmmode\pm\else\textpm\fi{}0.05$ meV for the exciton exchange energy. An anticrossing seen in the piezoluminescence data is attributed to an interaction, arising from the valence-band anisotropy, of the UPB with an optically forbidden triplet exciton state. Possible alternative explanations of the luminescence data are discussed and comparisons are made with earlier work.

Violet luminescence of Mg‐doped GaN

Abstract: The photoluminescent and electroluminescent properties of GaN–GaN:Mg diodes are described. Visible violet electroluminescence was observed with excitation voltages of 10–20 V with the emission peak in the region of 2.9 eV. The I‐V characteristics showed I ∞ V3 in the region where light was emitted, and the observed power efficiency was approximately 10−5. A photoluminescence peak at 2.9 eV provided additional evidence for an acceptor level, associated with the Mg impurity, about 0.5 eV above the valence band.

Properties of Epitaxial Gallium Arsenide from Trimethylgallium and Arsine

Abstract: Electrical and optical properties of epitaxial layers grown from trimethylgallium and arsine were studied by Hall and photoluminescence measurements The conduction type of the layers grown on substrates was changed from p‐ to n‐type with increase of , the mole ratio of arsine to trimethylgallium introduced, without intentional doping An emission (P2) at 1488 eV due to shallow acceptors was observed on most of the samplesCorrelations between the carrier concentration and the intensity of the P2 emission with suggest that the main acceptor impurities in the epitaxial layer are amphoteric ones on As sites, such as carbon and silicon contained in the trimethylgallium source Results of the mass‐spectrographic analysis of the layers are consistent with the above suggestion

Temperature, stress, and annealing effects on the luminescence from electron-irradiated silicon

Abstract: Low-temperature photoluminescence spectra are presented for Si crystals which have been irradiated with high-energy electrons. Studies of isochronal annealing, stress effects, and the temperature dependences of the luminescence are used to discuss the nature of the luminescent transitions and the properties of defects. Two dominant bands present after room-temperature anneal of irradiated material are discussed, and correlations of the properties of these bands are made with known Si defects. A band between 0.8 and 1.0 eV has properties which are related to those of the divacancy, and a band between 0.6 and 0.8 eV has properties related to those of the Si-G15(K) center. Additional peaks appear in the luminescence after high-temperature anneal; the influence of impurities and the effects of annealing of these lines are discussed.

Properties of Sn-doped GaAs

Abstract: The defect properties of GaAs have been investigated through a process of crystal growth, especially in relation to the change in electrical and luminescence properties and lattice constant due to the deviation from stoichiometry. GaAs crystals were grown from Sn solutions by the temperature gradient method under controlled As pressure from 8.5×10−‐6 to 4.3×10 Torr. From the photoluminescence measurements, the level which is associated with the As vacancy and Sn is found at 1.34 eV in the low As pressure region. With increasing As pressure, the concentration of the Ga vacancies which behave as acceptors increases and carrier compensation proceeds. The lattice constant is increased by the incorporation of Sn. It also is a function of the As pressure, that is, the Ga vacancy is found to make the lattice constant increase. It can be said that GaAs crystals which deviate from stoichiometry can be obtained when they are grown from Sn solutions under controlled As pressure.

Crystal synthesis, electrical properties, and spontaneous and stimulated photoluminescence of In1−xGaxP:N grown from solution

Abstract: The growth of In1−xGaxP from solution at constant temperature is described, and the distribution coefficient and incorporation of Ga in the crystal and also donor impurities are discussed. The variation of the measured mobility with composition indicates that the direct‐indirect transition is near x=0.74. Photoluminescence data on direct and indirect In1−xGaxP:N are presented, and the energies of the band gap, nitrogen A line, and NN‐pair peaks are plotted as a function of crystal composition. The nitrogen A line (EN) is degenerate with the Γ conduction‐band minimum (EΓ) at a crystal composition of x ∼0.71. For x≤0.71 a resonant N‐trap state exists above the fundamental conduction band edge. The resonant N‐trap transition can be photoexcited into laser operation in x=0.69 In1−xGaxP:N at very high energy (2.246 eV–5520 A, 77 °K) where, in fact, the recombination transition is enhanced (EN∼EΓ).

Edge and Donor-Acceptor Pair Emissions in Cadmium Telluride

Abstract: The luminescent properties of the edge and 1.42 eV emission bands in CdTe single crystals have been investigated in the temperature range from 140 to 4.2 K. Two distinct edge emission spectra (1.545 and 1.528 eV bands) are found in as-grown p-type crystals depending on crystal growth conditions. The time-resolved spectra and the dependence on the excitation intensity of the photoluminescence confirm that the 1.42 eV band which is usually observed in both n- and p-type CdTe is associated with transitions between donors and acceptors. The values of the ionization energy of donors and acceptors and some parameters involved in the pair emission are estimated.

Photoluminescence studies in irradiated Si-doped gallium arsenide

Abstract: In order to reveal the origin of the 1.40–1.42 eV band which is peculiar to Si-doped GaAs, elaborate investigations of photoluminescence spectra in irradiated and heat-treated Si-doped samples were carried out mainly at 77K. All experimental evidences supported the assignment that the band was caused from a complex of Si atom on As site with As vacancy. Unidentified emission bands at 1.305 and 1.44 eV were observed respectively in (Te + Si)-doped samples subject to electron irradiation and Si-doped samples fired in a dissociation As pressure.

Minority‐carrier lifetimes and luminescence efficiencies in nitrogen‐doped GaP

Abstract: Photoluminescence and scanning‐electron‐microscope measurements of minority‐carrier lifetime and luminescence efficiency have been made on Zn, N‐doped and Te, N‐doped GaP liquid‐phase‐epitaxy layers. Nitrogen concentrations are held constant at 1 × 1019 cm−3, while the majority‐carrier concentrations were varied between 5 × 1016 and 5 × 1018 cm−3. It is shown that, for excitation levels equivalent to 10 A/cm2 diode diffusion current density, a maximum external luminescence efficiency (in air) of 0.3% is measured for ∼1018‐cm−3 Zn, N‐doped GaP, in contrast to a maximum efficiency of 0.06% for ∼1017‐cm−3 Te, N‐doped GaP. These results suggest that significantly higher electroluminescent efficiencies approaching 0.3% are available for diodes at 10 A/cm2, by increasing injection into ∼1018‐cm−3 Zn, N‐doped GaP.

Photoluminescence in amorphous As2S3

Abstract: Photoluminescence in amorphous As2S3 has been investigated at temperatures down to 4 K, and excitation spectra are presented for the first time. The luminescence for evaporated films shows a substantial reduction on annealing, and this supports the model of Kilomiets (1970, 1972) in which recombination occurs via charged defects in the forbidden gap, formed by broken bonds. Luminescence is only observed with exciting photon energies corresponding to absorption coefficients of less than 104 cm-1, with the highest efficiency occurring at the lowest absorption. A model is discussed in which photons create exciton-like pairs in the vicinity of the charged defects.

Luminescence from In0.5Ga0.5P prepared by vapor‐phase epitaxy

Abstract: The photoluminescence from n‐ and p‐type In1−xGaxP with x≃0.5, prepared by vapor‐phase epitaxy on GaAs substrates, has been studied between 4.2 and 300 K. This material is of particular practical interest because of its close lattice‐parameter match with GaAs and direct energy band gap of 1.9 eV. At very low temperatures, four major emission bands have been identified, involving intrinsic recombination, donor—to—valence‐band transitions, conduction‐band—to—acceptor transitions, and donor‐acceptor transitions. The intrinsic recombination dominates in all the samples above about 150 K. The spectra are consistent with a shallow donor ionization energy of 7±1 meV, the same value as in InP. The spectral data of Cd‐doped samples (with p varying from 1.8×1016 to 9.3×1017 cm−3) suggest a consistent shift of the Cd acceptor ionization energy to lower values with increasing doping. The extrapolated value for very low doping is 59±2 meV at 50 K. The residual donor density is low in all the p‐type samples studied (≲ ...

Photoluminescence of GaSe

Abstract: Systematic photoluminescence measurements of the p- and n- type GaSe have been carried out in the temperature range between b.2 and 300 K. The main results, reported here, are: 1) direct free exciton emission centered at 2.109 eV; 2) a structured emission localized between 2.103 and 2.060 eV and attributed to excitons bound to neutral acceptors; 3) impurity states emission in the energy range between 2.057 and 1.904 eV.

Electroluminescence and photoluminescence of GaAs : Ge prepared by liquid phase epitaxy

Abstract: Optical data are presented relating the photoluminescence emission of GaAs : Ge epitaxial layers with hole concentrations in the range from 6 × 1016 to 2.7 × 1019 cm−3. These data are supplemented with electroluminescence results obtained using diodes where the p side of the junction consists of GaAs : Ge. Measurements reported include the peak position of the electroluminescence and photoluminescence peaks, half‐intensity bandwidths, and radiative efficiency at room temperature.

Fluoreszenz der magnetisch ordnenden Halbleiter EuS, EuSe und EuTe

Abstract: The photoluminescence properties of the europium-chalcogenides EuS, EuSe and EuTe are described. Below approximately 150°K these compounds show a characteristic near-infrared fluorescence band with a half-width of about 0.25 eV. This radiative recombination is ascribed to an intrinsic transition 4f 6 5d→4f 7 of the Eu-ions. Its important frequency shift with respect to the corresponding optical absorption in the vicinity of the absorption edge is due to a Franck-Condon-type relaxation process. The spectral band position and the quantum efficiency of the emission are found to be very sensitive to magnetic ordering. Within the series of substances the different kind of magnetic order is clearly illustrated by the dissimilar spontaneous fluorescence behaviour: On cooling, the ferromagnet EuS displays a red shift and a quenching of the emission nearT c, whereas the antiferromagnet EuTe shows a blue shift of the band and an increase of its intensity nearT N. With respect to this behaviour in zero field an applied magnetic field causes the fluorescence to be quenched and shifted towards longer wavelengths. The largest response to the field is observed in the vicinity of the ordering temperatures and in the metamagnetic temperature range of EuSe. The results are discussed in connection with measurements of the magnetization, the optical absorption and the photoconductivity and compared with fluorescence measurements on Eu(II)-silicates. The behaviour of the excitation spectra is closely related to the absorption edge shift. On the other hand the shift of the emission is not similarly discribed by the mean ion spin correlation. We propose to ascribe this to a magnetic relaxation in the vicinity of the excited state. The unusual intensity behaviour is also discussed.

Optical properties of photochromatic sulfur-doped chlorosodalite

Abstract: Synthetic.photochromic sulfo-chlorosodalite, 6(NaAlSiO4) ·2 NaCl(S), has been thoroughly investigated by measurements of optical absorption, photo-luminescence and cathodoluminescence. Depending on the sulfur ion form and concentration, the doped sodalite exhibits either sensitive tene-brescence or photoluminescence with long wavelength UV excitation. The photo-induced color absorption peaks at 5260A at 300°K with absorption coefficient, Δαmax >200 cm−1 . This is by far the highest photo-induced absorption observed for synthetic chlorosodalite. At 80°K, the peak position of the absorption does not show significant shift within instrumental accuracy. In photoluminescence, the emission spectra as well as the excitation spectra are studied at both 300 and 78°K. Four characteristic spectral bands (IR, blue, red, and a band with oscillation in wavelength) are observed. The oscillatory S2 - ion emission band starting about 2.35 eV and extending to lower energy and the IR band peaked at 1.4 eV are most efficiently excited by 3660A (3.4 eV), whereas the blue luminescence peaked at 2.7 eV has an excitation threshold of 3.9 eV. The red band is often masked by the oscillatory band and can be observed by higher energy excitation. The red and blue bands are also observable in the cathodoluminescence measurements of the sulfur-doped samples but not the undoped samples. Correlating the absorption, luminescence, and excitation spectral results, a quantitative model is derived to interpret the nature and the role of sulfur ions in the photochromic chlorosodalite material.

Photoluminescence of Color Filter Glasses

Abstract: The photoluminescence of color filter glasses (as typified by the complete Corning filter glass set) is characterized. Emission, excitation spectra, and decay times are determined, and quantum yield is estimated. For many of the filters, the quantum yield and range of excitation are such that fluorescence can be a (perhaps unrecognized) problem when these filters are used in a long-bandpass mode. Furthermore, interference filters are often not free from filter fluorescence because fluorescent glasses are commonly used as a substrate or as protection for the dielectric layers.

Photoluminescence ofn-GaAs at transparent Schottky contacts

Abstract: Near-bandgap photoluminescence at 300 K of a Se-dopedn-GaAs crystal withn=4.8·1016 cm−3 was measured at a transparent CrAu−GaAs Schottky contact. The dependence of the luminescence intensity on the applied reverse voltage was recorded. Both the doping concentration and absorption coefficients above bandgap are determined.