A Hall coefficient investigation of ferromagnetic Ga1−xMnxAs layers on (100) GaAs substrates

Ferromagnetic Ga1−xMnxAs epilayers with Mn mole fraction in the range of x≈2.2–4.4% were grown on semi-insulating (100) GaAs substrates using the molecular beam epitaxy technique. The transport properties of these epilayers were investigated through Hall effect measurements. The measured hole concentration of Ga1−xMnxAs layers varied from 4.4×1019 to 3.4×1019 cm−3 in the range of x≈2.2–4.4% at room temperature. From temperature dependent resisitivity data, the sample with x≈4.4% shows typical behavior for insulator Ga1−xMnxAs and the samples with x≈2.2 and 3.7% show typical behavior for metallic Ga1−xMnxAs. The Hall coefficient for the samples with x≈2.2 and 4.4% was fitted assuming a magnetic susceptibility given by Curie–Weiss law in a paramagnetic region. This model provides good fits to the measured data up to T=300 K and the Curie temperature Tc was estimated to be 65, 83 K and hole concentration p was estimated to be 5.1×1019, 4.6×1019 cm−3 for the samples with x≈2.2 and 4.4%, respectively, confirming the existence of an anomalous Hall effect for metallic and insulating samples.