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Abstract

A thorough study of wet thermal oxidation in AlAs/AlxGa1-xAs superlattices is presented. The results shown here demonstrate that the final oxidation depth can be finely tuned via the composition and thickness of AlxGa1-xAs into the digital alloy. A complete model of oxidation in these structures is proposed, relying on diffusion through the AlAs layer, its oxidation and an additional effect due to the AlxGa1-xAs intermediate barriers. This barrier contribution is shown to further improve the control of the oxidation rate, and thereby fabrication of sophisticated AlOx/GaAs integrated optoelectronic devices.

Abstract

Preparation of processed GaAs surface cleaning in view of molecular beam epitaxy regrowth by means of a O2SF6 microwave plasma has been investigated. Photoemission, Auger electron spectroscopy, atomic force microscopy and secondary ion mass spectrometry have been used for characterization. The O2SF6 plasma treatment was found to be very efficient for decontaminating the GaAs surface and leads to the formation of an oxide layer that can be taken off by a thermal or low temperature H-plasma assisted deoxidation. The levels of oxygen and carbon contaminants at the regrowth interface were measured to be in the range of a standard homoepitaxial layer-epiready substrate interface. Fluorine was observed to be eliminated upon deoxidation while sulphur is present, particularly in the case of low temperature grown layers. This plasma treatment was found to be efficient for preparation of processed GaAs surfaces for molecular beam epitaxial regrowth.

Abstract

We have developed integrated distributed-feedback laser arrays using photonic crystal waveguide on a membrane. They exhibit stable single-mode emission. Using both different lattice constants and a method called affine deformation of the crystal, we obtained extended control over the lasing wavelength. Laser arrays with laser-to-laser wavelength shifts as small as 0.3 nm are achieved.

Résumé

Des lasers tout cristal photonique émettant par la facette fabriqués dans le système (In)GaAs/AlGaAs et fonctionnant en régime de pompage optique sont démontrés. Nous montrons qu'une émission laser stable basée sur un point de fonctionnement de type DFB du second ordre peut être obtenue en utilisant des guides de type W3 (3 rangées de trous manquant). Nous démontrons la faisabilité d'une ingénierie de la longueur d'onde démission obtenue soit par modification du pas du cristal photonique (accord grossier), soit par déformation affine du cristal (accord fin). Nous étudions la sensibilité des cavités étudiées face aux conditions de pompage, à la longueur de cavité, et nous analysons la possibilité d'utiliser des guides plus larges.

Mots-Clés / Keywords

Abstract

We present a comprehensive study of spectral photoluminescence (PL), photoconductivity and Hall mobility in undoped, n and p-type modulation-doped quantum wells of Ga1x InxNyAs1y/GaAs with varying nitrogen concentration.We show that the increasing nitrogen composition red shifts the energy gap and this red shift is accompanied with a reduction of the 2D electron mobility in the quantum wells. True temperature dependence of the band gap, free from errors associated with nitrogen induced exciton trapping effects, is observed because in the modulation doped QWsamples PL emission is dominated by bandto- band recombination and the S-shape temperature dependence is eliminated. Excellent fit to semi-experimental Varshni equation is obtained and the temperature dependence of the band gap in the linear regime (dE/dT) is tabulated as a function of nitrogen concentration and the type of dopant.

Mots-Clés / Keywords