SBIR-STTR Award

This program is investigating the growth of gaas using ionized cluster beam (icb) technology employing substrate growth temperatures of less than 6000 c. Unintentionally doped epitaxial gaas has been grown on well characterized semi-insulating gaas substrates. The icb grown gaas is being thoroughly characterized. Recent work has been done on the deposition of SI semiconductor films for use in solar cell applications. Other work on iii-v films has also been addressed. This technique operates as a hybrid approach between mbe and ion implant. Using vacuum levels of 10-7 torr and accelerated ionized clusters, depositions of single crystal films have been done at reduced substrate temperatures. The use of this process to gaas could offer an epi process that operates at temperatures below 500 degree with large area uniformity in thickness and composition.

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.