100 research outputs found
Strained-Layer InGaAs(P)/InP Quantum Well Semiconductor Lasers Grown by Organometallic Vapour Phase Epitaxy
No full textApplied Science
TEMPERATURES AND FLOWS IN HORIZONTAL EPI REACTORS
No full textDans les réacteurs d'épitaxie horizontaux, des flux importants de gaz porteurs H 2, N2, He ou argon sont présents pour entraîner les constituants de croissance chimiquement actifs tels que SiHCl3, SiH4 pour la croissance de silicium par CVD ou les espèces de gallium et d'arsenic pour la croissance de GaAs en phase gazeuse. Des flux importants sont nécessaires pour avoir des vitesses de croissance égales sur toute la longueur du tube du réacteur. De cette manière, la dépression de la phase gazeuse est neutralisée. Les flux des quatre gaz porteurs ont été étudiés en détail pour différents types de réacteurs d'épitaxie horizontaux par des techniques de mesures optiques in-situ telles que l'holographie interférentielle. L'analyse des résultats montre clairement l'influence dominante des effets d'entrée, particulièrement importants pour l'argon et l'azote. H2 et He ont dans des conditions normales des lignes de flux laminaires bien développées,alors que N2 et Ar donnent en général un mélange de flux turbulents et convectifs, fortement sous-développés en vitesse et en température. Les figures d'interférence rendent possibles le calcul des profils de température dans le tube du réacteur. Cela a été fait pour plusieurs vitesses de flux et types de cellules de reacteurs. Dans ce cas, l'influence de l'effet d'entrée est vu moins clairement : il se manifeste par la présence d'un doigt froid dans le courant gazeux. D'autre part, dans le cas de CVD à basse pression, sont présents simultanément une plus faible pression et de plus grandes vitesses de flux. L'effet de ces paramètres sur les profils des flux est discuté. En plus, quelques calculs de T. Cherepanova donnent les profils de température en fonction des vitesses de flux des processus d'épitaxie. Dans ce cas aussi, l'échauffement du flux gazeux est le principal phénomène rencontré.In horizontal epitaxial reactors high flows are present of the carrier gases H2, N2, He or argon which carry the chemically active growth components e.g. SiHCl3, SiH4 for silicon growth by CVD or the gallium and arsenic species for the growth of GaAs from the gas phase. High flows are needed in order to achieve equal growth rates along the length of the reactor tube. In this way the depletion of the gas phase is counter acted. For various types of horizontal epitaxial reactors the flow of these four carrier gases has been studied in detail using in situ optical measuring techniques i.c. interference holography. Analysis of the results clearly shows the dominant influence of the so called entrance effects, which, especially are of importance for argon and nitrogen. It appears that H2 and He under normal conditions will have well developed laminar streamlines, whereas N2 and Ar nomally will give a mixture of turbulent and convective streams, which are highly underdeveloped qua velocity and temperature. The interference patterns make it possible to calculate the temperature profiles in the reactor tube. This has been done for several flow velocities and types of reactor cells. Here the influence of the entrance effect is most clearly seen : it demonstrates itself as the presence of a cold finger in the gas stream. In low pressure CVD besides the lower pressure also higher flow velocities are present. The effect of these parameters on the flow profiles is discussed. In addition some calculations made by T. Cherepanova are given on temperature profiles as a function of flow velocity for furnace processes. Also here the heating up of the gas stream is the main phenomenon which is encountered
The flash-photolysis of sodium pyrenide in tetrahydrofuran. On the photo-oxidation process and on the existence of sodium atoms NaO
No full textTHE INCORPORATION OF PHOSPHORUS IN SILICON; THE TEMPERATURE DEPENDENCE OF THE SEGREGATION COEFFICIENT
No full text
A closer study on the self-annihilation of antiphase boundaries in GaAs epilayers
No full textContains fulltext :
27678.pdf (Publisher’s version ) (Open Access
Vapour growth of silicon: growth anisotropy and adsorption
No full textThe development of facets on hemispherical single crystal substrates is investigated for growth in a near-equilibrium hot-wall CVD system, in order to study the orientation dependence of silicon crystal growth as a function of gas phase parameters in the Si-H-Cl system. It is found that only faces with indices {hhk} are stable. On the basis of their different behaviour as a function of experimental conditions, these faces are divided into {hhk}h k and {hhk}h < k faces. The {111} and {001} faces have to be considered separately. From the experimental dependencies it is concluded that the adsorption of chlorine and hydrogen plays a dominant yet ambivalent role: it stabilizes the {001} and the {hhk}h k faces, but destabilizes the {hhk}h < k faces. In order to explain these effects, it has to be assumed that under CVD conditions dimer-like reconstructions are present on all silicon faces. The interplay between surface dimer reconstructions and adsorption processes also shows up in the kinetic roughening of the different faces at high supersaturations. Theoretical calculations of the probabilities of adsorption of growth species on the different faces are used to explain the differences in kinetic roughening of these faces and the observed change in orientation of growth hillocks on the {111} faces which occurs when the supersaturation is increased
Chemical boundary layers in CVD II. Reversible reactions
No full textIn addition to irreversible reactions, which were treated in part I, reversible reactions in the gas phase have beenstudied using the concept of the chemical boundary layer. The analysis is given for the situations in which either the forwardor the back reaction is dominant. Two conceptual models for the boundary layer are used in the calculations: theblock model and the linearly varying k model. It is shown that both models lead to the same deposition rates
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