Hall-effect measurements in Cd-implanted GaAs

Abstract

Cadmium ions were implanted in GaAs crystals at 135 keV to doses ranging from 1012 to 1016 ion/cm2 at room temperature. Sheet-resistivity and Hall-effect measurements were carried out as a function of temperature, 4.2–300°K, after annealings at 700, 800, or 900°C in an Ar ambient. The sample surfaces were protected with pyrolytically deposited Si3N4. Significant p-type conduction was observed when samples with doses ≳1013 cm−2 were annealed at ≳700°C. For doses below 1014 cm−2 nearly complete electrical activity was attained after an 800–900°C anneal. The Cd profiles were determined by differential Hall-effect measurements in conjunction with the acid-etch layer-removal technique. Above about 800°C diffusion becomes important and significantly flattens the implantation profile.