Date of Award

Summer 1981

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Physics

First Advisor

Pedrotti, Frank L.

Second Advisor

Burch, Thaddeus J.

Third Advisor

Deshotels, Warren

Abstract

This work represents an initial investigation into the electrical properties of Gallium arsenide (GaAs), consecutively doped by ion implantation with two ion species, sulphur and gallium ions, at ion energies of 63 keV and 120 keV respectively. Theoretically at these energies maximum concentrations of sulphur and gallium occur at the same depth into the surface of the GaAs samples. The principal objective of this study is to determine whether the use of dual implantation of gallium and sulphur (Ga+S) can enhance the electrical activity of the resulting active layers when compared with the implantation of sulphur alone. The secondary objective is the comparison of two different substarte materials, semi-insulating chromium-doped substrate and epitaxial substrate, with regard to resulting dopant activation and carrier mobility. Room temperature ion implantation was performed at the Avionics Laboratory, Wright Patterson Air Force Base (WPAFB), Dayton, Ohio, on both type of GaAs samples in doses ranging from 5x1012ions/cm2 to 1X1015ions/cm2• Silicon nitride (Si 3N4 ) encapsulant was used during thermal annealing which was also performed at the Avionics Laboratory at 900 for 30 minutes. The electrical characterization of these samples was made at the Solid State Laboratory, Marquette University Physics Department, by using the van der Pauw technique. Sheet carrier concentration, sheet resistance, Hall sheet coefficient, Hall mobility and activation efficiency were calculated for each sample. The experimental results show that samples with single sulphur-implant generally yield higher activation in comparison to the dual implanted samples. Contrary to expectations, the dual implantation of Ga+S did not enhance the n-type activity of the S-dopant. It might happen that excess substitutional Ga-cations produced p-type activity which compensated the desired n-type activity due to S-implant. Also, a modification of damage centers might occur during implantation and high temperature annealing raising the level of electrical compensation.

Share

COinS