Effect of correlation between the shallow and deep metastable level subsystems on the excitonic photoluminescence spectra in <Emphasis Type="Italic">n</Emphasis>-GaAs

The excitonic photoluminescence spectra of GaAs epitaxial layers are studied. Changes in the relative arrangement of shallow and deep centers in the tetrahedral lattice are shown to bring about changes in the decay kinetics and the shape of the (D⁰, x) emission line (corresponding to an exciton bound to a shallow neutral donor). This change in the excitonic photoluminescence spectra is caused by dispersion in the exciton binding energy of shallow donors E_D, the dispersion being a result of the influence of the subsystem of deep metastable defects in n-GaAs crystals.     

Setup for taking the radiation spectra of wideband semiconductors

A setup is developed for measuring the spectra of wideband semiconductors (III nitrides) and related heterostructures. The setup makes it possible to trace the time distribution of the luminescence intensity at a fixed wavelength with a resolution of ±5 ns and a sampling rate of up to 10 MHz in the time interval from several microseconds to several hundreds of microseconds. Also, it plots the integral intensity of luminescence versus the wavelength. Precision measurement conditions are provided.     

Influence of the magnetic field and measurement temperature on the shape of microphotoluminescence spectra of Eu-Doped InGaN/GaN quantum-well structures

Based on the results of complex investigations of the influence of the magnetic field strength and measurement temperature on the shape of microphotoluminescence (micro-PL) spectra of Eu-doped InGaN/GaN quantum-well structures, the determination of the charge state of Eu impurity ions, and the change in the concentration of dopant ions, it has been shown that an increase in the magnetic field strength (0–5 T) leads to a more significant decrease in the luminescence intensity as compared to the undoped structures. An increase in the measurement temperature from 4.2 to 78 K results in an enhancement of the effect of the magnetic field on the shape of the micro-PL spectra of Eu-doped InGaN/GaN structures. It has been demonstrated that the doping of InGaN/GaN quantum-well structures with europium at a high excitation level leads to a shift in the maximum of the luminescence intensity toward the long-wavelength range of the spectrum.     

Growth and Structural,Magnetic, and Magnetooptical Properties of ZnO Films Doped with a Fe57 3d Impurity

Physics of the Solid State - ZnO films obtained by high-frequency magnetron sputtering and doped with a Fe57 metallic 3d impurity by the diffusion method are studied. The type of local environment...     

Intensity of visible and IR emission of intracenter 4<Emphasis Type="Italic">f</Emphasis> transitions of RE ions in Er- and Tm-doped ZnO films with additional Ag,Li, and N impurities

The use of Ag impurity in Er-doped ZnO films deposited by AC magnetron sputtering with a low growth rate has increased the emission intensity at λ = 1535–1540 nm. An increase in the deposition rate and in the temperature of substrates, as well as the use of Li and N⁺ impurities, led to a considerable increase in the intensity of the line with λ = 376–379 nm in the case of doping with rare-earth ions (Er, Tm), which makes it possible to use this semiconductor for creation of devices for the short-wavelength spectral region. Introduction of additional impurities in Er-doped ZnO films deposited on bulk ZnO crystals with increasing deposition rate and temperature caused an increase in the intensity of the line with λ = 1535–1540 nm. The photoluminescence spectra of ZnO films doped with Tm (ZnO<Tm>) exhibited intense emission of lines with λ_max = 377 nm.     

Parameters of thulium-doped gallium nitride crystals with wurtzite structure

A study was made of GaN crystals grown by HVPE and MOCVD. Thulium was introduced by diffusion. It is shown that the Tm rare-earth ion acts as an acceptor in a GaN semiconductor matrix if the undoped crystal contains deep-level defects. Intracenter f-f transitions characteristic of Tm were observed in the short-and long-wavelength spectral regions. The short-wavelength emission intensity is higher in crystals obtained by MOCVD.     

Radiation intensity fluctuations of an exciton Bose condensate in GaAs/Al0.33Ga0.67As double quantum wells

Fluctuations in time of the intensity of indirect exciton photoluminescence in GaAs/Al_0.33Ga_0.67As double quantum wells have been studied. An analysis of the behavior of the intensity fluctuations under variation in external control parameters, such as the temperature and the voltage applied perpendicular to the structure, has revealed that they directly reflect the manifestation of Bose condensation. It has been demonstrated that the current flowing perpendicular to the structure also undergoes pronounced fluctuations simultaneously with those of the intensity. A study of possible reasons that could account for the onset of such fluctuations suggests the need for taking into account tunneling transitions in the exciton Bose condensate system.     

Influence of Silver and Gold Nanoparticles and Thin Layers on Charge Carrier Generation in InGaN/GaN Multiple Quantum Well Structures and Crystalline Zinc Oxide Films

It has been shown that Ag and Au nanoparticles and thin layers influence charge carrier generation in InGaN/GaN multiple quantum well structures and crystalline ZnO films owing to the surface morphology heterogeneity of the semiconductors. When nanoparticles 10 < d < 20 nm in size are applied on InGaN/GaN multiple quantum well structures with surface morphology less nonuniform than that of ZnO films, the radiation intensity has turned out to grow considerably because of a plasmon resonance with the participation of localized plasmons. The application of Ag or Au layers on the surface of the structures strongly attenuates the radiation. When Ag and Au nanoparticles are applied on crystalline ZnO films obtained by rf magnetron sputtering, the radiation intensity in the short-wavelength part of the spectrum increases insignificantly because of their highly heterogeneous surface morphology.     

Edge photoluminescence spectra and the intensity of the intracenter <Emphasis Type="Italic">f</Emphasis>-<Emphasis Type="Italic">f</Emphasis> transitions in Er-and Sm-doped GaN crystals

Doping of GaN crystals prepared by various methods (HVPE and MOCVD) with various degrees of perfection of the mosaic structure, using rare-earth (RE) ions has been studied. An analysis of the shape of the photoluminescence spectra obtained before and after the doping showed that, as the defect concentration decreases, the intracenter f-f transitions characteristic of RE ions, at 1.54 and 0.54 μm in Er³⁺ and 0.72 μm in Sm²⁺, become observable. The intracenter f-f transitions of RE ions are seen, as a rule, in epitaxial layers with well-aggregated and relaxed domains and are absent in the case of a mosaic structure containing domains in the near-surface part of the epitaxial layer that are not fully coalesced. RE doping of the crystals under study was observed to initiate defect gettering. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 5, 2004, pp. 814–819. Original Russian Text Copyright ? 2004 by Krivolapchuk, Lundin, Mezdrogina, Nasonov, Rodin, Shmidt.     

Influence of europium doping on the sensitization of luminescence in GaAs/AlGaAs and InGaN/GaN quantum-well structures

A correlation between the photoluminescence spectra and structural parameters of Eu-doped quantum- well nanostructures InGaN/GaN and GaAs/AlGaAs is established. It is shown that the incorporation of rare-earth ions initiates lattice (as a rule, compressive) strains. The excitation migration in structures of high perfection stimulates transfer of nonequilibrium carriers to the ⁵ D ₂-⁵ D ₀ atomic levels of the Eu ion. In less perfect structures, the insertion of a rare-earth ion leads to the formation of isovalent traps in GaN layers capable of effectively capturing nonequilibrium carriers, which increases the intensity of photoluminescence of the structure by one order of magnitude.