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ABSTRACT: We estimated the energy-transfer rate between an erbium (Er) 4f shell and a Si host by using two independent measurements. The first method involved measuring the temperature dependence of the decay time of Er 4f-shell luminescence and obtaining the energy-transfer rate by assuming that the energy transfer is assisted by nonradiative multiphonon processes and that thermal quenching is due to an energy back-transfer mechanism. The estimated value was 2×108 s−1. The second method involved measuring the time response for luminescence intensity after pulsed host photoexcitation. Although some tens of μs luminescence delay after host excitation has been reported, we found that the slow response time of the detection system may cause spurious delay. We measured the luminescence decay curve using a system with a fast response time and analyzed the data, taking into account the system response time. The energy transfer rate was estimated to be at least 107 s−1. This estimation is consistent with the result obtained by the first method, mentioned above, confirming a rather large energy-transfer rate between the Er 4f shell and Si host. © 1998 American Institute of Physics.
Journal of Applied Physics 10/1998; 84(8):4471-4478. · 2.17 Impact Factor
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ABSTRACT: Er-doped GaAs codoped with oxygen was studied by site-selective measurements of photoluminescence spectra and photoluminescence-excitation spectra directly exciting the 4f-shell electrons of one kind of Er center at a time. Within one sample, more than 10 kinds of distinctly different Er centers, showing different Er-related spectra, were observed, although its host-excited photoluminescence spectrum is dominated by the luminescence from one kind of Er center. The atomic configuration of that center has been identified as an Er atom located at the Ga sublattice with two adjacent oxygen atoms (Er-2O center). Seven kinds of Er centers in GaAs:Er, O and two kinds of Er centers in AlGaAs:Er, O were studied in detail. The numbers of lines and the magnitudes of energy separations among the lines in each spectrum indicate that the Er atoms of all nine kinds of centers are coupled with oxygen atoms and have noncubic symmetry. The nine Er centers were grouped into several classes according to similarities in their spectra which should reflect symmetries of the Er centers. The atomic configurations of two classes of Er centers are discussed in detail. The Er centers of both classes have a nearest-neighbor site atomic configuration similar to that of the Er-2O center with a symmetry close to rhombic C2v, but Er centers in the two classes have different types of deviation from C2v due to the difference in the second-nearest-neighbor atomic configurations of the Er atoms. We also discuss a large difference in the efficiency of the Er-related luminescence under host photoexcitation caused by the difference in the second-nearest-neighbor atomic configurations. © 1997 American Institute of Physics.
Journal of Applied Physics. 10/1997; 82(8):3997-4005.
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ABSTRACT: An optical spectroscopic study of Er-related luminescence in GaAs:Er,O as a function of temperature and applied hydrostatic pressure is reported. We observed the appearance of different Er-related luminescence under the application of hydrostatic pressure. The temperature dependence of the luminescence intensities for three kinds of Er centers as a function of pressure is measured and discussed in terms of the trap levels formed by the Er centers. It is shown that the energy-transfer process between photoexcited carriers in the host and the 4f shell of the Er3+ ion may occur when trap levels associated with an Er center enter the band gap under the application of hydrostatic pressure.
Phys. Rev. B. 10/1997; 56(16).
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ABSTRACT: We report a spectroscopic study of GaAs:Er,O samples grown by metalorganic chemical vapor deposition, with excitation in the near‐band‐edge region, 1.22–1.62 eV. Photoluminescence under host‐excitation is dominated by luminescence due to the Er‐2O center (an erbium atom at a gallium site coupled with two adjacent oxygen atoms) in these samples. The characterization of different Er centers is demonstrated by the observation of <sup>4</sup>I 15/2 →<sup>4</sup>I 11/2 intra‐4f‐shell transitions by photoluminescence excitation (PLE) spectroscopy. The transitions between these crystal‐field‐split 4f‐shell levels are observed at ∼1.26 eV (∼980 nm) which is at an energy attainable by PLE spectroscopy with a Ti:Sapphire laser. Two lines are assigned to the Er‐2O center. This allows a semi‐quantitative measurement of the relative concentrations of different centers to be made. PLE spectroscopy was also employed to study the trap levels related to the Er‐2O center. However, we find no evidence for such a trap level in this energy range. The expected position of this trap is discussed in the light of these results and recent calculations. © 1996 American Institute of Physics.
Journal of Applied Physics 07/1996; · 2.17 Impact Factor
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ABSTRACT: For GaAs:Er,O the anisotropic photoluminescence (PL) properties of the Er-20 center and its preferential alignment within the GaAs matrix have been revealed by the polarization dependence of host-excited PL when detecting emission polarized along certain crystallographic directions. In the present paper, a polarized intra-4f-shell photoluminescence excitation (PLE) spectroscopic study of Er centers incorporated in GaAs is reported. This technique is not only sensitive to those centers which luminesce under host-excitation, but also to other Er centers incorporated in the host, thus allowing the polarized PL properties of most Er centers to be studied. A comparison of the polarization characterisitcs of host-excited PL and direct intra-4f-shell PLE, due to the difference in the excitation mechanisms, is made and the information which may be gained from such measurements is discussed. For the Er-20 center, we confirm the optical anisotropy and preferential alignment of the center previously observed in host-excited PL. Incorporation mechanisms for the Er-20 center which could result in the observed polarization dependence are discussed.
MRS Proceedings. 12/1995; 422.
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ABSTRACT: GaAs grown by metalorganic chemical vapor deposition and codoped with Er and oxygen shows a simple spectrum with sharp luminescence lines due predominantly to one type of Er center. This center is identified as an Er atom substituting a Ga site, coupled with two oxygen atoms. Photoluminescence measurements under host excitation and photoluminescence excitation measurements that directly excite the 4f-shell of the Er3+ ion indicate that this center is excited much more efficiently than other Er centers simultaneously present in the same sample. A possible energy-transfer mechanism and its implications are discussed.
MRS Proceedings. 12/1995; 422.
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ABSTRACT: Er‐doped GaAs grown by metalorganic chemical vapor deposition was studied by photoluminescence and photoluminescence excitation (PLE) measurements using a color center laser that provides tunable light in the 1450–1550 nm range. The light in this wavelength region can directly induce the <sup>4</sup>I 15/2 →<sup>4</sup>I 13/2 intra‐4f‐shell transition of Er<sup>3+</sup> ions. The PLE spectra of a specific Er center formed by oxygen codoping under suitable growth conditions were conclusively assigned by site‐selective spectroscopy. Non‐site‐selective PLE spectroscopy, on the other hand, revealed that the atomic configurations of Er<sup>3+</sup> ions change according to the Er concentration, growth temperature, and oxygen codoping. Sharp lines related to Er<sup>3+</sup> ions with well‐defined atomic configurations, and inhomogeneously broadened structures related to aggregates of Er<sup>3+</sup> ions, are evident in the PLE spectra. The PLE spectra due to the direct intra‐4f‐shell excitation also revealed semiquantitatively that there are Er centers that do not show luminescence under above‐band gap photoexcitation, because of low energy transfer efficiency from the host. © 1995 American Institute of Physics.
Journal of Applied Physics 03/1995; · 2.17 Impact Factor
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ABSTRACT: This article investigates the structure of an Er luminescence center in GaAs by using its intra‐4f‐shell luminescence spectrum as an atomic probe to identify the atomic configuration. This Er center is formed in GaAs by metalorganic chemical vapor deposition with O codoping and the center shows a high efficiency and a sharp luminescence spectrum under above‐band‐gap photoexcitation. A single luminescence line in the spectrum of a GaAs:Er,O splits into more than eight lines in the spectrum of Al 0.01 Ga 0.99 As:Er,O. This drastic change due to the addition of 1% Al can be explained by assuming that, because of the high tendency of Al atoms to react with O atoms, the Al atoms preferentially occupy the nearest‐neighbor Ga sites of two O atoms, both of which are coupled with the Er atom. Based on the luminescence spectra and additional experiments of Rutherford backscattering and secondary ion mass spectroscopy, we propose that the structure of the Er luminescence center under study is Er occupying the Ga sublattice with two O atoms most likely located at the nearest‐neighbor As sites. An Er‐related spectrum of GaAs 0.97 P 0.03 :Er,O can also be understood based on this model if the chemical difference of Al and P is taken into account.
Journal of Applied Physics 11/1994; · 2.17 Impact Factor
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ABSTRACT: Comparison of the temperature dependencies of the
intra-4 f -shell photoluminescence (PL) and free electron
concentration in Yb-doped InP reveals that two mechanisms dominate the
thermal quenching of this PL. One is the localized Auger effect, which
is effective in samples with an excess donor concentration. The other
mechanism is independent of n- and p-type impurities and has an
activation energy of about 150 meV. Investigation of the relationship
between the temperature dependencies of the band-edge related PL and the
4 f -shell PL indicates that this is due to the energy back
transfer from the Yb 4 f -shell to the host electronic
state
Indium Phosphide and Related Materials, 1991., Third International Conference.; 05/1991
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ABSTRACT: The excitation and quenching mechanism of intra‐4f‐shell luminescence of Yb ions incorporated in an InP host is discussed. The discussion is based on experimental results of photoluminescence excitation spectra and photoluminescence time‐decay curves for crystals grown by metalorganic chemical vapor deposition and liquid‐phase epitaxy. The present as well as previously reported experimental results for samples grown by various methods can be consistently interpreted by considering a recently reported Yb‐related acceptorlike electron trap near the conduction‐band edge and by taking into account the shallow donor and acceptor as well as Yb concentrations in the samples. A model is proposed which describes the Yb intra‐4f‐shell excitation and quenching mechanisms for samples with various concentrations of the impurities.
Journal of Applied Physics 12/1989; · 2.17 Impact Factor
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ABSTRACT: The characteristics of the observed electroluminescence from the
internal 4 f -4 f transitions of Er<sup>3+</sup>, at 1.54
μm, and Yb<sup>3+</sup>, at 1.00 μm, are reported and compared
with an emphasis on the temperature dependence of the emission
intensity. In the erbium-doped LEDs the emission at 1.54 μm shows a
gradual decline in intensity with increasing temperature up to about 200
K, followed by a more rapid decline up to room temperature. The total
drop in intensity is about a factor of 20 from 77 K to room temperature.
This contrasts with the ytterbium-doped LEDs, for which the
rare-earth-related intensity drops sharply with temperature above 77 K
and is unobservable at room temperature. Such a difference implies a
significant difference in the active energy transfer mechanisms for the
two rare earth species. On the other hand, the temperature dependence of
the intensity in the erbium-doped devices appears to be relatively
insensitive to the host material (InP or GaAs). In addition, no
significant difference was observed in the peak position of the
1.54-μm emission between the GaAs devices and that of the InP devices
at 77 K and above
IEEE Transactions on Electron Devices 01/1989; · 2.32 Impact Factor
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ABSTRACT: GaAs light-emitting diodes emitting at 1.54 μm have been
fabricated using Er-doped GaAs grown by metal organic chemical vapour
deposition, and the output characteristics are reported for the first
time. Characteristic emission from the internal 4f-shell transitions of
erbium is observed even at room temperature, and the wavelength shifts
by less than the measurement resolution of 1 nm over the temperature
range from 180 K to 296 K. These results confirm the possibility of
fabricating stable light sources using rare earth doped semiconductors
Electronics Letters 07/1988; · 0.96 Impact Factor
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ABSTRACT: Room temperature aging tests have been carried out on molecular beam epitaxially grown InGaAs/InP BH (buried heterostructure) lasers with LPE (liquid phase epitaxy) InP burying layers and LPE‐grown InGaAs/InP BH lasers. Both types of lasers have operated continuously at room temperature in air for more than 8000 h at 4–8 mW/facet, and are still operating stably. Except for slight changes in the threshold currents at an early stage of the aging test, these lasers did not show noticeable change in the longitudinal mode, far field pattern, and light output response under pulsed operation before and after aging.
Journal of Applied Physics 03/1984; · 2.17 Impact Factor
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ABSTRACT: Preliminary results of the accelerated aging test under stresses of temperature and current are presented. The degradation modes are found to be divided into two patterns which can be mapped in co-ordinates of these stresses.
Electronics Letters 02/1983; · 0.96 Impact Factor
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ABSTRACT: Details of the fabrication, optimization of the dimensions of the active region, characteristics, and the aging results of the V - grooved substrate buried heterostructure (VSB) InGaAsP/InP laser are described. It is shown that the VSB laser can be fabricated in one-step epitaxy as well as two-step epitaxy. The active region width below 2.5 μm and the thickness of 0.15-0.2 mu m are shown to give stable fundamental mode operation and good temperature characteristics. The fundamental mode operation up to the optical output of 20 mW/facet at 25°C and the CW operation above 100°C are obtained. The pulse response showed the strongly damped relaxation oscillation with a frequency as high as 4.5 GHz. The spectral width under the modulation of 400 Mbit/s RZ single is as narrow as 25 Å in full width at half maximum. Highly stable aging characteristics at an elevated temperature of 50°C are obtained in both two-step epitaxy lasers and one-step epitaxy lasers.
IEEE Journal of Quantum Electronics 11/1982; · 1.88 Impact Factor
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ABSTRACT: Formation of oxide on mirror facets was observed by Auger electron spectroscopy in InGaAsP/ InP buried heterostructure lasers. The oxide on the mirror facets caused increase of threshold current and leakage current, and decrease of differential quantum efficiency. Such phenomena were observed under nonlasing high current density operation as well as under high optical output power operation. The degradation of lasers due to the mirror facet oxidation is shown to be suppressed by coating the mirror facet with Al 2 O 3 .
Applied Physics Letters 08/1982; · 3.84 Impact Factor
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ABSTRACT: Output power saturation of BH lasers under high current operation is analysed and it is concluded that such saturation is due to increase of leakage current through the burying layers. The mechanism of such leakage can be explained by a turn-on model of the bipolar transistor around the active region.
Electronics Letters 02/1982; · 0.96 Impact Factor
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ABSTRACT: Buried‐heterostructure InGaAsP/InP lasers with chemically etched mirrors are fabricated successfully. The lasers emit light at ∼1.5 μm. The threshold current of these lasers is nearly the same as that of conventionally fabricated cleaved‐mirror lasers. This fabrication procedure enables us to obtain low‐threshold‐current devices and allows a much wide variety of device design and fabrication compared with the conventional cleaving technique.
Journal of Applied Physics 10/1981; · 2.17 Impact Factor
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ABSTRACT: Fabrication and lasing characteristics of InGaAsP/InP lasers emitting around 1.55 μm are described. Zn-diffused stripe-geometry lasers with emission wavelengths in the 1.53-1.60mu m range were fabricated from InP/InGaAsP/InP DH epitaxial wafers prepared by a low temperature LPE technique. The dependence of the lasing charaeteristics on the stripe width was examined. The lowest threshold current (≃160 mA under CW operation at 27°C) was obtained for a laser with a 13 μm stripe. CW operation of the laser has been achieved at a heat-sink temperature as high as 53°C. For sufficiently narrow stripe widths ( simeq6 mu m), fundamental-transverse mode and single-longitudinal mode operation was obtained under CW operation. Moreover, the lasers have good high-frequency performance. The lasers showed excellent dynamic properties without waveform distortion under high-frequency (800 Mbits/s) large-signal pulse modulation. The full width at half maximum of the longitudinal mode envelope was approximately 30 Å at 800 Mbits/s.
IEEE Journal of Quantum Electronics 05/1981; · 1.88 Impact Factor
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ABSTRACT: A V-grooved substrate buried-heterostructure laser emitting at 1.3 ¿m wavelength is described. The active layer is buried in the V-shaped groove. A CW threshold current of 10~20 mA is obtained and a far-field pattern free from irregularity and peak shift is realised. Damped relaxation oscillation and stable aging characteristics are obtained.
Electronics Letters 02/1981; · 0.96 Impact Factor
