The objective of this proposal is the growth of high quality epitaxial GAS on GAAS substrates. The work will study the relationship between thermally neutral clusters and epitaxial film properties as well as the influence of ionized and accelerated clusters on film parameters. Particular emphasis will be directed to efforts to grow films at temperatures below 400 degree c. The native defects grown into the samples in the Phase I program were the result of high energy ions hitting the surface from small clusters. This work will address the problem of cluster formation conditions and cluster size. These critical parameters will, in turn, be related to multitude of machine modifications such as crucible modification, heater redesign, temperature control, and flux density studies. The films grown will be characterized by optical microscopy, hall, c/v, photoluminesence and Sims techniques. The Sims will be used to study impurities at the interface and in the bulk. One of the final objectives will be the study of selective doping of the films with both n-type or p-type dopants. The type of dopant will be varied as well as choice of using a gaseous or solid source.
