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.