Magneto-Optical Spectroscopy on (Ga,Mn)As Based Layers—Correlation Between the p–d Exchange Integral and Doping

Abstract

It is well established that the ferromagnetism of (Ga,Mn)As is mediated by holes. An important parameter in this context is the p–d exchange integral N ₀β as the RKKY interaction parameter J _RKKY is proportional to (N ₀β)². In magnetic semiconductors, magnitude and sign of N ₀β are strongly dependent on the local electronic configuration of the Mn-ion and on the free carrier density. To investigate the correlation between the p–d exchange interaction and doping in Ga_1−x Mn _x As, paramagnetic samples with x ≈0.1% have been intentionally n-doped with Te. High-field Hall measurements at 1.6 K confirm that with increasing degree of Te co-doping, the samples change from p- to n-type. The magnetic field induced splitting of the excitonic and electronic states has been studied by various magneto-optical spectroscopic techniques at 1.8 K and external magnetic fields up to 7.5 T. The p–d exchange integral changes from N ₀β > 0 (ferromagnetic coupling) to N ₀β < 0 (antiferromagnetic coupling) with increasing degree of Te co-doping. Thus, N ₀β can be tuned and can even change its sign in dependence on the doping conditions of the Mn-containing layers.