Showing papers on "Photoluminescence published in 1968"
TL;DR: In this paper, the broad-band photoluminescence spectra typical of bulk-grown or low-purity epitaxial GaAs breaks into a number of sharp emission lines in very-highpurity GaAs, and the assignments are based on dependence of the emission lines with temperature, impurity content, and carrier type ($n$- or $p$-type material), as well as on the relative energy positions.
Abstract: The broad-band photoluminescence spectra typical of bulk-grown or low-purity epitaxial GaAs breaks into a number of sharp emission lines in very-high-purity GaAs. At low temperatures (\ensuremath{\sim}2\ifmmode^\circ\else\textdegree\fi{}K), emission peaks due to free excitons (1.5156 eV), excitons bound to neutral (1.5145 eV) and ionized (1.5133 eV) donors, and excitons bound to neutral (1.5125 eV) and ionized (1.4886 eV) acceptors are identified. Also, band-acceptor (1.4926 eV) and donor-acceptor (1.4857 eV) recombination is observed. The assignments are based on dependence of the emission lines with temperature, impurity content, and carrier type ($n$- or $p$-type material), as well as on the relative energy positions. The temperature dependence of the exciton-neutral-donor complex appears to be influenced by nonradiative Auger recombination.
205 citations
TL;DR: In this paper, the radiative processes in closely compensated GaAs doped with Si (p•type) and Si+Te (n−type) have been studied by photoluminescence between 300° and 77°K.
Abstract: The radiative processes in closely compensated GaAs doped with Si (p‐type) and Si+Te (n‐type) have been studied by photoluminescence between 300° and 77°K. These materials were grown by liquid‐phase epitaxy. The results strongly suggest that Si introduces two acceptor levels in GaAs with ionization energies of approximately 30 meV and ∼100 meV. In the n‐type material containing Si and Te only the radiative transition involving the deeper acceptor is observed (hvp∼1.44 eV at 77°K). In moderately Si‐doped, p‐type material (∼1018 cm−3 range), transitions involving both levels are observed. The apparent ionization energy of the deeper level moves to higher energies with increasing Si concentration while the shallow acceptor band appears to merge with the valence band. In the p‐type material, the electron transitions are assumed to originate at deep states (>40 meV) in the ``tail'' of states below the conduction band introduced by the high Si donor concentration. An intense broad emission band centered in the range 1.26 to 1.23 eV at 77°K is observed in some p‐type specimens. This band is attributed to an acceptor level 230±20 meV above the valence band. It is tentatively suggested that it involves an As vacancy or As vacancy complex.
126 citations
TL;DR: In this paper, the photoluminescent properties of the edge emission and the self-activated emission of pure zinc selenide crystals were studied and the binding energy of the acceptor involved in the selfactivated emission was determined from the thermal quenching of the luminescence.
Abstract: The photoluminescent properties of the edge emission and the self-activated emission of pure zinc selenide crystals were studied. The spectra of the edge emission at liquid helium temperature and the self-activated emission show peak shifts to lower energies with decreasing the intensity of excitation and also with time after excitation. These are conspicuous characteristics of the donor-acceptor pair recombination. The binding energies of the donor and the acceptor relevant to the edge emission were obtained from time-resolved spectra. The binding energy of the acceptor involved in the self-activated emission was determined from the thermal quenching of the luminescence. It is likely that the donor involved in the self-activated emission is shallow and closer pairs contribute to the spectrum as compared to the low temperature edge emission. The self-activated emission is excited efficiently by the host absorption and the quantum efficiencies are as high as 25% and 70% at room and liquid nitrogen temperat...
75 citations
TL;DR: In this paper, a detailed investigation has been made of the density-of-states distribution of the deeper acceptor levels and the experimental data have been compared to the theory of Morgan, which considered the effect of the screened Coulomb potential due to charged impurities on the density of deep recombination centers.
Abstract: A study was made of photoluminescence in n‐ and p‐type Ge‐doped GaAs grown by liquid‐phase epitaxy and of electroluminescence of Ge‐compensated diodes. It is shown that two radiative emission bands are observed at 77°K, which are due to acceptor levels at Eν+0.03 eV and Eν+0.07 eV introduced by Ge. The shallow level is attributed to isolated Ge atoms on As sites, while the deeper level is believed to consist of an atomic complex involving Ge. The density of the deeper centers relative to the shallower ones depends on the growth conditions. In the samples studied, the deep center density is 102 to 103 smaller than the shallow center density. A detailed investigation has been made of the density‐of‐states distribution of the deeper acceptor levels and the experimental data have been compared to the theory of Morgan. This model considered the effect of the screened Coulomb potential due to charged impurities on the density‐of‐states distribution of deep recombination centers. The present materials are of par...
62 citations
TL;DR: In this article, a study was made of n-type GaAs prepared by liquid phase epitaxy doped with Si, Ge, Sn, Te, and Se by photoluminescence and Te-doped material by transmission-electron microscopy.
Abstract: A study was made of n‐type GaAs prepared by liquid‐phase epitaxy doped with Si, Ge, Sn, Te, and Se by photoluminescence and Te‐doped material by transmission‐electron microscopy. A broad emission band centered at 1.2 eV (band B) is observed in LPE materials doped with group VI elements. Band B increases in intensity relative to the bandgap radiation with increasing dopant concentration in the 1018 cm−3 range. It is suggested that the recombination centers responsible for band B are the neutral (VGa+3 Te) complexes postulated by Vieland and Kudman, and that these represent the solid solution of Ga2Te3 in GaAs. With increasing dopant content, the solubility limit is eventually exceeded, and precipitates of this compound are then formed. These have been observed and identified by transmission‐electron microscopy. The radiative efficiency falls off sharply with increasing dopant content beyond 2–3×1018 cm−3 in materials doped with Se and Te. It is suggested that this fall off is partly due to nonradiative rec...
53 citations
TL;DR: In this paper, a study of the photoluminescence spectra of Sn-doped GaAs grown by liquid phase epitaxy was made, in which, because of growth under As deficient conditions, compensation is expected to occur by the possible occupation by Sn atom of As sites.
Abstract: A study has been made of the photoluminescence spectra of Sn‐doped GaAs grown by liquid‐phase epitaxy, in which, because of growth under As deficient conditions, compensation is expected to occur by the possible occupation by Sn atom of As sites. Hall data suggest that some compensation does take place by the formation of Sn acceptor levels. A broad emission band was found at about 1.26 eV (77°K) whose peak position follows closely the temperature‐dependent variation of the bandgap energy. This band was not seen in materials grown from the melt. It is suggested that the band is due to an acceptor 0.2±0.02 eV above the valence band edge. Evidence is inconclusive for the existence of a shallow acceptor due to Sn similar to that introduced by Si and Ge in GaAs. Thus, the deep level may be due to Sn on isolated As sites, rather than to a complex involving Sn atoms. The radiative band due to this deep acceptor exhibits unusual structure below 77°K, which is explained as an electronic transition to a tightly bo...
35 citations
TL;DR: In this article, thermal conversion in quenched GaAs is caused both by copper acceptors and by shallow acceptors which are responsible for the 1.49 eV emission band in the original GaAs.
Abstract: GaAs crystals grown from the melt in silica boats without intentionally doping exhibit n‐type conductivity. Photoluminescence measurements at 20°K are used here to study thermal conversion in these crystals. Heat treatments with temperature TH ranging from 600° to 1100°C followed by quenching were performed on three crystals with different carrier concentrations. For TH≥900°C, it is concluded that the thermal conversion in quenched crystals is caused both by copper acceptors and by the shallow acceptors which are responsible for the 1.49 eV emission band in the original crystals. The latter acceptors are suggested to be silicon. It is proposed that conversion associated with silicon results from transfer of silicon atoms from donor sites to acceptor sites through a trapping process during rapid quenching. The maximum compensation due to these shallow acceptors is estimated, depending on the crystal used, to be on the order of 5×1016 cm−3 at 1100°C and is smaller at lower temperatures. For TH≤870°C, it app...
34 citations
TL;DR: In this article, the authors used electron-irradiated samples with reported luminescence data on non-stoichiometric specimens to identify the role and energy levels of a number of defects in cadmium telluride.
Abstract: By combining low temperature luminescence measurements on electron-irradiated samples with reported luminescence data on non-stoichiometric specimens it has been possible to identify the luminescence role and energy levels of a number of defects in cadmium telluride. Cadmium and tellurium vacancies are shown to produce energy levels 0·036 ev and 0·46 ev above the valence band respectively. Using electrons from a Van de Graaff accelerator and observing photoluminescence and cathodoluminescence emission spectra at liquid helium temperatures the displacement energies of tellurium and cadmium have been found to be 7·8 ev and 5·6 ev respectively. The defects introduced by low temperature electron irradiation have been shown to produce emission characteristics which are not observed in specimens grown from the melt. It is suggested that this is the result of the strong perturbation of the electronic wave functions of a cadmium vacancy by the displaced cadmium atom at a nearby interstitial site.
33 citations
TL;DR: In this article, the photoluminescence energy of an Al-Ga alloy was observed to shift from those of GaP by 0.10 eV to higher energies.
Abstract: Aluminum‐doped GaP has been grown from solution with concentrations up to 30% Al. The crystals are stable and do not corrode in air. Evidence that the system is forming an Al–Ga alloy is provided by an observed shift of the absorption edge and photoluminescence from those of GaP by 0.10 eV to higher energies. The green photoluminescence peaking at 2.306 eV (4.2°K) is studied and identified as pair emission. A weak band at 1.92 eV is also seen, analogous to the highly efficient Zn–O red band at 1.82 eV in Al‐free GaP. The implications of this shift in photoluminescence energy are discussed.
29 citations
TL;DR: In this paper, it was shown that the luminance of SiC with Al can be resolved into two similar structures corresponding to the recombination of an electron with a hole trapped in the Al centre.
25 citations
TL;DR: In this paper, it was shown that the centers associated with the 1.370 eV photoluminescence band are VAsZnGa or DAsZNGa pairs, where VAs and DAs denote an As vacancy and a donor impurity occupying an As site.
Abstract: A number of changes in the 1.370 eV photoluminescence band are observed in Zn‐doped GaAs after heat treatment in molten KCN, Ga, or diffusion with Cu at temperatures ranging from 235° to 1100°C. The band is replaced by a CuGa− band at 1.356 eV after Cu diffusion under intrinsic conditions and can be eliminated or preserved, respectively, by heat treating the crystal in molten KCN or Ga above 650°C. Emission of a broad band near 1.37 eV with a sharp‐line structure appears after saturation with Cu at temperatures between 550° and 370°C. The structure has a zero‐phonon line at 1.429 eV and additional lines separated by about 0.011 eV. No change in the shape of the 1.370 eV band is seen for heat treatment below 550°C in the absence of copper. It is proposed that the centers associated with the 1.370 eV band are VAsZnGa or DAsZnGa pairs, where VAs and DAs denote an As vacancy and a donor impurity occupying an As site, and that the centers responsible for the band with sharp‐line structure are VAsCuGa or DAsCuG...
TL;DR: In this article, the authors used photoluminescence measurements at 20°, 77°, and 300°K to investigate radiative recombination via the near gap transition in p-type GaAs after heat treatment with excess arsenic pressure, PAs4.
Abstract: Photoluminescence measurements at 20°, 77°, and 300°K are used to investigate radiative recombination via the near gap transition in p‐type GaAs after heat treatment with excess arsenic pressure, PAs4. The heat treatments are performed at 800°C for 24 h. For heavily doped crystals of Zn acceptor concentration NA≃5×1018 cm−3, the intensity of the Zn photoluminescent line, I(hv1), is independent of PAs4 up to pressures as high as 3 atm. For lightly doped materials of NA+ND≃8×1016 cm−3, I(hv1) ∝ (PAs4)−1/4 for PAs4 >2×10−1 atm. These results can be attributed to Ga vacancies or associates of Ga vacancies with other defects which dominate the nonradiative recombination at low acceptor concentration and to acceptor impurities which dominate the nonradiative recombination at high acceptor concentration. The transitions corresponding to shallow defect levels at 1.480 eV are found to disappear after heat treatment.
TL;DR: In this paper, a defect center model was proposed to explain the photoluminescence spectra of Zn-doped GaAs after copper diffusion under extrinsic conditions.
Abstract: A new defect center model is proposed to explain the photoluminescence spectra of Zn‐doped GaAs after copper diffusion under extrinsic conditions. These centers introduce a broad band which is located at about 1.37 eV and shows a sharp‐line structure. Photoluminescence data taken from samples Cu‐diffused at different temperatures for different lengths of time are analyzed to obtain the kinetics of the formation of the defect. It is found that the formation kinetics is of first‐order with an activation energy of 1.65 eV. The defects are suggested to be VAsCuGa or DAsCuGa pairs, where VAs and DAs denote, respectively, an arsenic vacancy and a donor impurity occupying an arsenic site.
01 Jan 1968
TL;DR: In this paper, the external quantum efficiency of an electroluminescent diode is predicted from measurements on the annealed wafers on the basis of the above information.
Abstract: The most important device parameter of an electroluminescent diode is the external quantum efficiency. This in turn is influenced by the properties of the junction (injection efficiency), by the recombination processes in the bulk material (recombination efficiency), and by the optical properties of the semiconductor (optical efficiency). This paper shows how the three effects can be separated by measuring photoluminescent efficiencies in various dielectric media along with electroluminescent efficiencies and Hall parameters. The external electroluminescent quantum efficiency of the diode can be predicted from measurements on the annealed wafers on the basis of the above information.
Abstract: Samples of strontium oxide on nickel alloy or platinum substrates show a blue-green luminescence when excited at 100°K with photons of energy greater than 39 ev. The emission spectrum shows peaks at 21, 28 and 31 ev, the 31 ev peak increasing in intensity as the oxide sample is subjected to thermionic activation. Illumination of the oxide sample causes an enhancement of both photoelectric and thermionic emission, which can be reduced by heating the oxide. The most efficient photon energies for producing the enhancement are those in the 40-55 ev range. The enhancement effects may be due to photon-induced population of a broad band of metastable donor levels at about 20-35 ev below vacuum potential. Comparison of the wavelengths of luminescence emission and excitation peaks in barium oxide, calcium oxide and strontium oxide samples suggests that the same types of luminescence centre occur in each alkaline earth oxide.
TL;DR: In this paper, the basic luminescence properties of zirconium silicates activated by manganese, chromium, hafnium, and rare-earth elements were examined.
Abstract: The article considers the basic luminescence properties of zirconium silicates activated by manganese, chromium, hafnium, and rare-earth elements. The absorption, excitation, photoluminescence and radioluminescence spectra, the thermal bleaching, attenuation, and temperature-induced attenuation were examined. The term scheme of the Na2ZrSiC5 crystal phosphor was constructed. The luminophors examined are stable with respect to heat, moisture, and corrosive chemical compounds.