Showing papers by "Benoit Deveaud published in 1984"

Observation of one-monolayer size fluctuations in a GaAs/GaAlAs superlattice

Abstract: The observation of one‐monolayer well size fluctuations in a superlattice is reported. Luminescence experiments show that several exciton peaks occur, each of them corresponding to a discrete well width differing by one monolayer from the next one. This attribution is confirmed by the intentional introduction of a larger well in the structure. It is also checked by comparison with the x‐ray diffraction results that confirm the variations of the superlattice parameters observed in luminescence, and by photoluminescence excitation experiments that also show a splitting.

Luminescence processes at chromium in GaAs

Abstract: In GaAs:Cr, the ${\mathrm{Cr}}^{2+}$ internal luminescence is not observed when excited with above-gap light, because the $^{5}E$ state of ${\mathrm{Cr}}^{2+}$ is above the conduction-band minimum. We report here on experiments which allow one to observe this luminescence: luminescence in ${\mathrm{Ga}}_{x\ensuremath{-}1}{\mathrm{Al}}_{x}\mathrm{As}$:$\mathrm{Cr}$, luminescence in GaAs under hydrostatic pressure, or luminescence in GaAs excited with a yttrium-aluminum-garnet:neodymium laser at 1.32 \ensuremath{\mu}m (0.9 eV). The zero-phonon line of that luminescence is observed for the first time and corresponds well to the absorption line. It is shown that in any case the radiative transitions are the results of a balance between the internal transition ($A$) and the band-to-level transition ($B$). Photoluminescence excitation spectra of the various luminescence bands involving ${\mathrm{Cr}}^{2+}$ are reported, and they allow one to confirm the previously proposed schemes. A model is developed, in terms of one-electron orbitals, to explain the characteristics of the photoluminescence excitation processes for ${\mathrm{Cr}}^{2+}$ as well as for other transition-metal ions in III-V materials. Internal luminescence at ${\mathrm{Cr}}^{2+}$ is shown to be mainly excited through the capture of electronhole pairs by ${\mathrm{Cr}}^{2+}$ centers. This model allows one to propose some kind of Auger effect to explain the ${\mathrm{Cr}}^{2+}$-related photoconductivity in III-V compounds. Finally, various band-shape calculations are performed that lead to the conclusion that spin-orbit effects on the band shape are negligible and that the main effect is due to a quadratic Jahn-Teller effect in the $^{5}E$ excited state.

Deep levels related to Co in InP

Abstract: Electrical and optical junction space‐charge spectroscopies,photoluminescence, and electron paramagnetic resonance are used to investigate the charge states of Co present in n‐type InP and to characterize the deep levels occuring in such Co dopedmaterials.Electron paramagnetic resonance and photoluminescence results indicate unambiguously that the Co2 + charge state is present in n‐type material substitutional to indium. Only one deep level at E V +0.24 eV is detected with a concentration similar to Co doping. The (E V +0.24 eV) level is identified with the (Co2 +→Co3 ++e C B ) charge state change mainly on the analysis of its optical cross sections σ0 n (hν) and σ0 p (hν). Optical transitions are well interpreted as transitions from the Co2 + ground state (4 A 2) to the Γ point minimum of the conduction band for σ0 n (hν) and from the valence band to the Co2 + ground (4 A 2) and excited state (4 T 2) for σ0 p (hν). The value of the ionization energy for Co2 + in InP (1.16 eV) is shown to agree quite well the value predicted by the trends of the ionization energies of 2+ charge states of transition metals in III‐V semiconductors.

Observation of a new chromium‐related complex in GaAs:Cr

Abstract: A new zero‐phonon line in GaAs:Cr is observed at 0.844 eV. This line is attributed to an internal transition of a Cr2+‐Te complex. Photoluminescence excitation experiments are reported for the first time on the 0.839‐eV line (Cr2+–X). Comparison of the results on these two centers with those obtained on isolated Cr2+ gives interesting details about the trigonal field at Cr2+–X and Cr2+‐Te. Other complexes are not suspected to be observed in luminescence.

Device has electro-optical semiconductor device and method of light emission

Abstract: THE INVENTION CONCERNS A DEVICE ELECTRO-OPTICAL FOR MAKING A LIGHT RADIATION FROM A MID SEMICONDUCTOR SUBJECT TO CONTROLLED EXCITEMENT ENERGY. THE ENVIRONMENT IS A SEMICONDUCTOR ALLOY SEMICONDUCTOR III-V bINARY, TERNARY AND QUATERNARY FORM OF AT LEAST ONE COLUMN III AND AT LEAST ONE COLUMN V THE PERIODIC TABLE, AND DOPED vANADIUM AND TITANIUM. THE DEVICE IS MADE MORE PARTICULARLY IN THE FORM OF OR eMITTING DIODE LASER.