Wafer Mapping of Material and Device Properties in Variously Prepared GaAs Substrates

Full wafer mapping of structural and electrical properties has been used to evaluate the various methods of preparing GaAs substrates. X-ray topographs and wafer maps of IR absorption, microwave photoconductance, and ion implantation activation reveal significant variations between wafers grown by standard LEC and those grown with In-alloying or by gradient freeze. The effects of post- growth annealing in the boule or wafer stage are presented as well. Correlation of the observed material properties with FET threshold voltage uniformity will also be discussed.