Doping effect on the properties of III-V ferromagnetic semiconductor GaMnAs epilayers and their superlattices

We present a systematic study on the properties of the ferromagnetic (FM) III-V-based semiconductor GaMnAs, including extrinsically doped GaMnAs : Be and its heterostructures in the form of superlattices. In an attempt to further improve the Curie temperature T, of GaMnAs, we have undertaken a systematic program of extrinsic p-doping of this material. In GaMnAs with low x (x = 0.03), T-c is, indeed, seen to increase monotonically with increasing Be doping. We also studied the effect of p-doping of non-magnetic spacer layers on the magnetic properties of GaMnAs/GaAs superlattices (SLs). While Be-doped SLs exhibited relatively robust remanent magnetization and a larger coercivity over a broad temperature range, undoped SLs showed a fast decrease in the remanent magnetization with temperature, and a rather small coercivity. We propose that the observed hardness of the magnetization in SLs with Be-doped GaAs layers is related to the interlayer coupling introduced by the doping of the non-magnetic layers.