Abstract
Some of the effects of implanting tellurium and tin into single crystal gallium arsenide are described in this thesis. The distribution and retention of tellurium and tin implanted into GaAs, the properties of the ion implantation damage and the. electrical properties of the ion implanted impurities were studied as a function of the implantation temperature, dose and anneal temperature between 150°C and 700°C. Silicon dioxide (SiO[2]) was used as the encapsulant for the majority of those specimens annealed at temperatures in excess of 500°C. A few comparative measurements were made with silicon nitride (Si[3]N[4]) as the encapsulant material. The effectiveness of silicon dioxide as an encapsulant for GaAs is discussed. The Rutherford backscattering and Hall effect techniques were used to investigate the depth distribution of the physical and electrical properties of the ion implanted layers. It was shown that the damage induced conductivity was confined to a thin surface layer for implantation temperatures of 20°C and 100°C, but deeper diffusing tails in the electrical conductivity versus depth profile were observed for implantation temperatures of 180°C and 250°C. The dependence of the damage induced conductivity on analysis temperature could be described theoretically by a model in which it was assumed that the conduction mechanism was similar to that of an amorphous semiconductor with a non-uniform density of states in the region of the Fermi energy level. Although the ion implanted Te does not redistribute for annealing temperatures up to 700°C, the ion implanted Sn diffuses towards the surface of the crystal. The results presented indicate that, for anneal temperatures up to 700°C, only a small percentage of the ion implanted Te and Sn became electrically active. The reasons for this low activity are discussed.