The Influence of Substrate Properties on the Electrical Characteristics of Ion-Implanted GaAs

Abstract

The type of substrate used for the formation of n-type layers in GaAs by ion implantation has a pronounced effect on the electrical properties of the implanted and annealed layers. Certain Cr-doped semi-insulating substrates exhibit a marked decrease in sheet resistance during the anneal cycle. We find that the carrier concentration of the converted material increases with the background Si concentration in the starting material. The carrier concentration profile and mobility of implanted and annealed GaAs are dependent on the substrate. The most reproducible and the highest quality layers with regard to mobility and carrier profile are obtained in high purity LPE or high purity bulk starting material. Results from 13 high purity ingots, grown during a one-year period at HP, demonstrate the quality and reproducibility of the layers produced by direct implantation into these substrates.