The Transport of Gallium Arsenide in the Vapor Phase by Chemical Reaction

Abstract

The heat contents and entropies have been derived as a function of temperature for gallium arsenide and the gaseous species which exist in equilibrium with it, in the temperature range 800~176 when iodine or hydrogen chloride and hydrogen are also present. The important gaseous species are shown to be GaC13, GaIs, GaC1, GaI, HI, I2, I, HC1, As4, and H2. Under certain conditions the species As2, AsC13, and Ga (liq.) may also be present. The free energy changes for reactions among the above species are derived. They are shown to be consistent with those isothermal equilibria that have been directly measured. The free energy changes are used, together with the conservation equations for nondepositing components (I, C1, H, and As in excess of the stoichiometric Ga: As: 1:1 ratio) to give the partial pressures of all the important species at any temperature in a temperature gradient in a constant pressure system. The results are applicable to the calculation of the flux of gallium arsenide in open flow or closed tube (diffusive transport) systems, and they are in good agreement with experimentally measured rates of transport in the system GaAs-H2-C12 in an open flow apparatus.

Analysis of performance-limiting defects in pn junction GaAs solar cells grown by water-mediated close-spaced vapor transport epitaxy

“…We are currently designing and building such a system in our laboratory. A theoretical analysis of GaAs halogen transport in a closedtube is given by Fergusson and Gabor [42] and experimental results for GaAs and GaP have been described by Moest and Shupp [43]. In the latter study, epitaxial growth was reported with T src = 700 -800 °C and T sub = 500 -640 °C indicating lower deposition temperatures can be used with HCl.…”

GaCl molecular beam cell for surface dynamics studies

“…Reaction equilibrium constants k a , k b , and k c of reactions ͑a͒, ͑b͒, and ͑c͒ are given in Table I. 8,9 Since k b exceeds k a , the majority of GaCl production reaction is through the route from reaction ͑b͒ to reaction ͑c͒. Because k c is smaller than k b , reaction ͑b͒ occurs more easily than reaction ͑c͒, indicating that the GaCl 3 by-product is generated under an excess supply of Cl 2 gas.…”

Cinétique du transport de matière dans un tube ouvert

“…-Nous avons estimé que, compte tenu des faibles dimensions de la source par rapport au tube, le champ de vitesses ne pouvait être considérablement perturbé, surtout pour les vitesses linéaires mises en jeu ici (vo, définie à la température ambiante To, variant de 0,1 à 2 cm.s-1); aussi, avons nous considéré que ce champ était uniforme et parallèle à l'axe du tube. L'équation (10) n'est alors plus nécessaire et l'équation (9) se réduit à : où v (pour vx) devient la vitesse linéaire définie à la température T.…”

“…-La cinétique de transfert de matière en phase vapeur, d'une source chaude vers une zone froide, a été abordé dans de nombreux articles, mais essentiellement pour le transport en tube fermé ( [1] ] à [9]). Nous avons développé ici la cinétique du transport de matière en tube ouvert, beaucoup moins étudiée que la précédente ( [10] à [12]) et ayant donné lieu à peu de comparaisons théorieexpérience. L'étude de ce transfert de matière au sein d'une phase vapeur est importante car elle permet ensuite de mieux aborder et d'approfondir la cinétique de dépôt sur un substrat, généralement positionné en zone froide (T,).…”