Wafer mapping of material 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. KOH etching, wafer maps of IR absorption and microwave photoconductance, as well as full wafer measurements of resistivity and ion implantation activation reveal significant variations between wafers grown by standard LEC, and those given a post growth anneal, or grown with in-alloying, or by gradient freeze. The uniformity of implantation behavior was found to correlate strongly with the uniformity of the material properties measured. Of the methods tested, boule annealing proved to be most effective techniques for improving material uniformity.