Split and normal gate A1GaAs /GaAs MODFETs were fabricated along with the ohmic test structures and the Hall bar geometries. The DC characteristics of normal gate transistors were evaluated at room temperature and at 77K and the threshold voltages were extracted from the measurements and compared to the theoretical results. The performance of normal gate transistors was reasonable. The sheet carrier density and the mobility extracted from Hall measurements using the Hall bar geometry showed increase of carrier density with increasing gate voltage and an increase of mobility with increasing carrier density. The contact resistance obtained from the ohmic test structure was high and not uniform within the sample. / Graduation date: 1991

Not available / text

No description available.

No description available.

No description available.

No description available.

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xx, 187 p.; also includes graphics (some col.). Includes bibliographical references (p. 174-187). Available online via OhioLINK's ETD Center

This thesis reports the development of two rapid thermal annealing systems, one based on resistive heating of graphite strips, the second on heating from incoherent lamp radiation. Electrical activation studies of silicon implanted gallium arsenide has been used to compare the systems with those available commercially. It has been shown that commercial systems can yield temperature measurement errors in excess of 50° C. Furthermore, the systems have been used to investigate the electrical activation of silicon implants co-implanted with other ions into gallium arsenide, with a view to either, improving the activation of the silicon for high doses, or modifying the carrier profile shape for low doses. A factor of two improvement in the electrical activation of high dose silicon implants has been achieved by the co-implantation of phosphorus, with a reduction in the annealing temperature required to achieve a given activity also being observed. An alternative processing methodology is also proposed for through- nitride implantation. Phosphorus implants have also been used to "pre-amorphise" substrates to prevent ion channelling. Providing the damage is maintained below a certain level, improvements in profile shape can be obtained. Other compensation techniques using boron and carbon implants have also been investigated. Boron has been demonstrated to provide improved carrier activation for low implant doses, with thermally stable profile modification capability as the dose is increased. The electrical activation of single carbon implants (40% maximum) is below the level of compensation of silicon implants (approximately 90%) co-implanted with carbon. This in turn means carbon is excellent for profile modification as no p-type layer is created beyond the donor implant.