THE GROWTH OF QUANTUM WELL GaAs/GaAlAs LASER STRUCTURES

Dans ce papier nous décrivons la croissance des interfaces abruptes pour l'application des lasers à puits quantiques. Nous rapportons les caractéristiques d'une structure Laser GRIN-SCH à puits quantique qui a montré la plus petite densité de courant de seuil jamais rapportée (232 A cm2 pour une longueur de cavité de 413 µm) tout en conservant de bonnes propriétés themiques et électriques. Une comparaison des longueurs d'ondes d'émission obtenues avec celles que la théorie laisse prévoir nous a permis d'étalonner la vitesse de croissance de la couche active entre 60 Å et 400 Å et d'estimer que la largeur de l'hétérointerface est inférieure à 10 Å.In this paper we describe the growth of abrupt heterojunctions for use in quantum well laser applications. We give the characteristics of a GRIN-SCH quantum-well laser structure which exhibits the lowest threshold current density ever reported (232 A cm2 at a cavity length of 413 µm) while maintaining good thermal and electrical properties. A comparison of the emission wavelengths with those predicted theoretically has allowed us to calibrate the growth rate in the layer thickness range 60 Å to 400 Å and to estimate a heterointerface abruptness of less than 10 Å

THE OMVPE GROWTH OF GaAs AND GaAlAs ON A LARGE SCALE

Ce papier décrit une tentative positive d'industrialisation de la méthode organométallique, effectuée à deux niveaux. Premièrement avec le système GaAs/GaAlAs on a essayé différentes géométries de suscepteurs placées dans un réacteur horizontal pour faire des diodes lasers sur des surfaces supérieures à 50 cm2. Deuxièmement un réacteur vertical de grande capacité capable de traiter 20 plaques de diamètre trois pouces a été conçu et réalisé en collaboration avec la Société "Métal Research" pour assurer la croissance de GaAs. Les caractéristiques des couches : uniformité de composition d'épaisseur et de dopage sont discutées pour chacune des géométries.In this paper we discuss the design of "scaled up" OMVPE reactors and describe the characteristics of a horizontal reactor for which we have designed a susceptor geometry having a capacity of 60 cm2 of substrate. This is followed by a description of the growth behaviour of a very large scale vertical reactor, which was designed in collaboration with Metals Research and has a capacity of 900 cm2, i.e. twenty 3" slices of GaAs

Determination of the structural and luminescence properties of nitrides using electron backscattered diffraction and photo- and cathodoluminescence

In this paper we describe the use of electron backscattered diffraction (EBSD) for the characterisation of nitride thin films, and report its use in the study of the spatial variation of strain across an epitaxially laterally overgrown GaN (ELOG) thin film. We also discuss the combination of luminescence and EBSD measurements to enable luminescence properties of samples to be directly correlated with their crystallographic properties. We compare photoluminescence spectra and EBSD measurements from a set of GaN thin films grown on off-axis sapphire substrates, revealing the tilt of a GaN thin film grown on a 10° off-axis sapphire substrate to be responsible for the observation of luminescence defect bands in this film. We finally report on the use of EBSD to identify zinc blende regions in a predominantly wurtzite MBE film, with cathodoluminescence used to obtain correlated luminescence spectra

Characterisation of nitride thin films by EBSD

Thin films incorporating GaN, InGaN and AlGaN are presently arousing considerable excitement because of their suitability for UV and visible light-emitting diodes and laser diodes. However, because of the lattice mismatch between presently used substrates and epitaxial nitride thin films, the films are of variable quality. In this paper we describe our preliminary studies of nitride thin films using electron backscattered diffraction (EBSD). We show that the EBSD technique may be used to reveal the relative orientation of an epitaxial thin film with respect to its substrate (a 90° rotation between a GaN epitaxial thin film and its sapphire substrate is observed) and to determine its tilt (a GaN thin film was found to be tilted by 13±1° towards [10 0]GaN), where the tilt is due to the inclination of the sapphire substrate(cut off-axis by 10° from (0001)sapphire towards (10 0)sapphire). We compare EBSD patterns obtained from As-doped GaN films grown by plasma-assisted molecular beam epitaxy (PA-MBE) with low and high As 4 flux, respectively. Higher As 4 flux results in sharper, better defined patterns, this observation is consistent with the improved surface morphology observed in AFM studies. Finally, we show that more detail can be discerned in EBSD patterns from GaN thin films when samples are cooled