An optical study of interdiffusion in ZnSe/ZnCdSe

Copyright 1996 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Applied Physics Letters 69, 1579 (1996) and may be found at

Stimulated emission and optical gain in a single MOVPE-grown Zn x Cd 1 − x S e − Z n S e quantum well

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Light amplification due to free and localized exciton states in ZnCdSe GRINSCH structures

International audienceIn this paper we present measurements of light amplification in optically pumped ZnCdSe GRINSCH (graded refraction index separate confinement heterostructures), In several differently designed samples we observe the presence of two gain mechanisms, which involve localized excitons and exciton-exciton inelastic scattering processes, respectively. The influence of the GRINSCH sample structure on gain is discussed in terms of their improved light-guiding properties

Stimulated emission of optically excited MOVPE grown ZnCdSe-ZnSe GRINSCH quantum well

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Positron annihilation in ZnSe layers grown on GaAs: Zinc vacancies and drift in the electric field at the ZnSe/GaAs interface

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Characterization of ZnSe epitaxial layers by four-wave mixing experiments

International audienceFour-wave mixing experiments in two- and in three-beam configurations have been performed at room temperature on ZnSe layers grown by two different techniques: high quality ZnSe layers grown on a GaAs (001) substrate by low-pressure metal-organic vapour phase epitaxy and pulsed laser deposited ZnSe layers on GaAs (001). The GaAs substrates were first removed by polishing and chemical etching. The linear optical properties of the ZnSe epilayers have been studied by photoluminescence, reflection and transmission measurements, in order to analyse the quality of the samples. The third-order nonlinear susceptibility chi((3)), has been measured by degenerate four-wave mixing in the two-beam configuration near the absorption edge at room temperature. chi((3)) values of 3.4 x 10(-4) acid 1.8 x 10(-4) esu respectively have been obtained at about 2.7 eV close to the band edge of the two types of samples.The dynamics of photocreated free carriers has also been studied in the same samples by four-wave mixing experiments in the three-beam configuration at room temperature. A lifetime T-1 = 720+/-20 ps and an ambipolar diffusion coefficient D-a = 5.0+/-0.3 cm(2) s(-1) have been obtained for metal-organic vapour phase epilayers and compared with previously published results. The carrier recombination in the laser-deposited samples has been shown to be much faster, probably due to their higher concentration of crystalline defects. For all the samples studied, the homogeneous dephasing time T-2 was found to be shorter (< 2 ps) than the temporal resolution of our experimental set-up

Thermal stability of GaN investigated by Raman scattering

We have investigated the thermal stability of GaN using Raman scattering. Noninvasive optical monitoring of structural damage to GaN by high-temperature anneals in nitrogen ambient has been demonstrated. Characteristic features in the Raman spectrum identify three thermal stability regimes. Thermal damage between 900 and 1000 degrees C results in the appearance of a broad Raman peak between the E-2 and A(1) (LO) phonon. For anneals at temperatures higher than 1000 degrees C emerging macroscopic disorder gives rise to distinct Raman modes at 630, 656, and 770 cm(-1). Below 900 degrees C no thermal damage has been observed. The evolution of the Raman spectrum of GaN with increasing annealing temperature is discussed in terms of disorder-induced Raman scattering. We find clear indications for a reaction at the GaN/sapphire interface for anneals higher than 1000 degrees C. (C) 1998 American Institute of Physics

Growth and characterisation of Eu doped GaN thin films

We have studied the optical properties of Eu doped GaN thin films. We have grown high quality Eu doped GaN thin films by using Gas Source Molecular Beam Epitaxy (GSMBE), with 1.4% Eu concentration. The Full Width at Half Maximum (FWHM) of the X-ray diffraction in an omega scan was found to be 288 arcsecs. Low Eu concentration (0.08%) doped GaN thin films were grown, where Eu-related photoluminescence at 622 and 613 nm was detected using above band-gap excitation at 2 K. For high Eu concentration of 30% GaN:Eu crystal photoluminescence (PL) and cathodoluminescence (CL) spectra show strong and intense transitions at 622 and 664 nm, but also at 593 nm for CL spectra, with a similar transition observed from the low Eu concentration sample