Photoluminescence fatigue of ZnSe semiconductor under ultraviolet irradiation (original) (raw)
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Time-resolved photoluminescence of isoelectronic traps in ZnSe1−xTex semiconductor alloys
Applied Physics Letters, 2008
Kohlrausch’s stretched exponential law correlates well with the photoluminescence (PL) decay profiles of ZnSe1−xTex. As the Te concentration increases, the stretching exponent β initially declines and then monotonically increases. This result can be understood using the hopping-transport and energy transfer model. The increase in the number of isoelectronic Te localized traps can reduce the PL decay rate and increase the linewidth, whereas the hybridization of the Te localized states with the valence-band edge states causes a reduction in both the lifetime and linewidth.
Effect of Annealing on Photoluminescence Properties in Ar+-Ion Irradiated MOCVD-Grown ZnSe Films
Japanese Journal of Applied Physics, 1988
Ion irradiation and subsequent thermal annealing effects have, for the first time, been investigated on photoluminescence properties at 4.2 K of ZnSe films grown on (100) GaAs and Ge substrates by metalorganic chemical-vapour deposition (MOCVD). After irradiation of Ar+-ion beams with a total dose of about 1015 cm-2 at 50 KeV, the deep-level emission bands newly appear in the vicinity of about 570 nm, while the excitonic emission lines become extremely weak in intensity or vanish completely. It is found that the photoluminescence spectra in ZnSe/Ge are almost completely recovered by annealing at 350°C. On the contrary, in the case of ZnSe/GaAs, the deep-level emission bands around 570 nm become much greater in intensity after the anneal. It is therefore suggested that the 550, 570 and 600 nm bands which occur in the irradiated ZnSe/GaAs, are derived from complex defects associated with radiation-induced Zn vacancies and/or donor impurities out-diffused from the substrate.
Microstructural study of quantum well degradation in ZnSe-based laser diodes
physica status solidi (c), 2004
The possibility to grow CdZnSSe quantum structures with a high structural quality is extremely important for light emitting devices in the blue-green spectral range. However, during device operation the degradation of the quantum well reduces the lifetime severely due to the formation of dark spot and dark line defects, which are not clearly understood. To investigate the mechanisms of defects formation degradation studies were performed for ZnSe-based laser diodes with quaternary CdZnSSe quantum well structures by means of electroluminescence, high-resolution X-ray diffraction and transmission electron microscopy. It was found that the degradation is closely connected to a blue shift of the emitted light and the formation of defects which are confined near to the quantum well. A partial broadening of the quantum well could be observed, which is attributed to the outdiffusion of Cd from the active region.
Applied Physics Letters, 1999
Photoluminescence lifetimes have been measured at room temperature as a function of carrier density in ZnCdSe/ZnSSe quantum wells. We show that, at low carrier density (5ϫ10 9 -5 ϫ10 10 cm Ϫ2 ), nonradiative recombination dominates, while radiative recombination becomes more dominant as the carrier density is increased from 5ϫ10 10 to 5ϫ10 11 cm Ϫ2 . Above ϳ5 ϫ10 11 cm Ϫ2 , band filling effects are shown to produce a saturation of the lifetimes. A simple rate equation model approach can be used to describe the carrier density dependence of the photoluminescence decay data obtained on a wide range of samples. A representative band-to-band recombination coefficient of 8ϫ10 Ϫ4 cm 2 s Ϫ1 and a Shockley-Read-Hall rate of 7.3ϫ10 7 s Ϫ1 were determined for one of the better samples studied. We believe that the excellent quality of our samples has allowed for the radiative recombination coefficient to be characterized accurately at room temperature.
Spectral structure of the X-ray stimulated phosphorescence of monocrystalline ZnSe
Physica B: Condensed Matter, 2015
This work presents the extensive experimental studies of the X-ray stimulated luminescence, conductivity, phosphorescence and electric current relaxation, and the thermally stimulated luminescence and conductivity of monocrystalline ZnSe. It was found that the luminescence emission band with a maximum at 635 nm is a combination of at least three emission bands and that the appropriate recombination centres implement both electronic and hole recombination mechanisms. We propose an energy model of the traps and recombination centres in monocrystalline ZnSe and show that the majority of the generated free electrons and holes recombine in the luminescence centres with an estimated probability of 94.3% and that only a small fraction (5.7%) of generated charge carriers are accumulated in traps during the X-ray excitation of the ZnSe sample.
Japanese Journal of Applied Physics, 1983
The successful results on surface gettering of background impurities and defects in 1.6 mm thick (111) GaAs wafers have been obtained. For the gettering, the wafers were coated by a 1000 Å thick yttrium film either on one side or on both sides followed by a heat treatment. It has allowed the electron concentration to decrease from (1-2)×10 15 cm -3 down to 10 8 -10 10 cm -3 and the mobility to increase from 1500-2000 cm 2 V -1 s -1 up to 7000 cm 2 V -1 s -1 at 300 K. The distribution profiles of the electron concentration and of the hole effective lifetime throughout the wafer thickness as well as photoluminescence spectra at 2 K have been presented.
Photoluminescence in Chemical Vapor Deposited ZnS: Insight into electronic defects
Optical Materials Express, 2013
Photoluminescence spectra taken from chemical vapor deposited (CVD) ZnS are shown to exhibit sub-band-gap emission bands characteristic of isoelectronic oxygen defects. The emission spectra vary spatially with position and orientation with respect to the major axis of CVD growth. These data suggest that a complex set of defects exist in the band gap of CVD ZnS whose structural nature is highly dependent upon local deposition and growth conditions, contributing to inherent heterogeneity in optical behavior throughout the material.
Time-resolved photoluminescence spectroscopy of individual Te impurity centers in ZnSe
Physical Review B, 2006
Time-resolved photoluminescence ͑PL͒ measurements are carried out for the InGaAs quantum dots ͑QDs͒ grown on ͑001͒ and ͑311͒ oriented GaAs substrates. The detection energies scan the spectral region from the energy of the QD excitonic transition up to the wetting layer absorption edge. A convex-shaped decay of the PL signal in this region gives evidence of carrier relaxation through the continuum states below the wetting layer similar to a diffusion process. Strong dependence of the decay time on the excitation density observed for the QD ground-state PL is consistent with a presented theoretical model.
LUMINESCENCE AND LASING IN ZnSe MICROPOWDERS AT HIGH OPTICAL EXCITATION LEVELS
Photoluminescence (PL) of ZnSe wide-bandgap semiconductor micropowder was studied at a high optical excitation level by pulsed nanosecond N2-laser emission. A new emission band that appeared on the long-wavelength edge of the PL spectrum at 40–75 meV from the electron–hole plasma (EHP) band depending on the optical excitation level showed that plasmons could participate in recombination processes in the EHP. Random lasing at 475 nm from submicron-sized crystallites in ZnSe powder was produced by the third harmonic of a YAG:Nd3+ laser with an exciting-radiation threshold intensity of 750 kW/cm2. The lasing manifested as a sharp increase of integrated emission intensity, a narrowing of the spectrum, and the appearance in it of localized and extended mode structure. Random lasing was due to feedback of amplifi ed radiation in closely packed active scattering microcrystallites.
Defect characterization of electrically degraded ZnSe based laser diodes
physica status solidi (a), 2004
The degradation of the optical active region of a CdSe/ZnSe based laser diode was analyzed in detail by use of transmission electron microscopy. The investigated structure contained a separate confinement structure in the active region and was degraded by operating the device below the lasing threshold. The defect formation is connected with a local relaxation of the quantum well and a Cd outdiffusion occurring along extended defects, which are confined to the quantum well. These defects are more pronounced into the p-type side of the laser diode.