Valence Band Dispersion in Mn, Bi and In doped GaAs

Impact of Bi and In incorporation into (Ga,Mn)As layers on their electronic- and band-structures as well as their magnetic and structural properties has been studied. Homogenous (In,Ga,Mn)As, (Ga,Mn)(Bi,As) and (In,Ga,Mn)(Bi,As) layers of high structural perfection have been grown by the low-temperature molecular-beam epitaxy technique. Post-growth annealing treatment of the layers results in an improvement of their structural and magnetic properties and an increase in the hole concentration in the layers. Hard-x-ray angular-resolved photoemission spectroscopy (HARPES) reveals a strongly dispersed band, crossing the Fermi energy in the highly Mn-doped layers, appearing because of high concentration of Mn-induced itinerant holes residing in the valence band. Moreover, an increased density of states near the Fermi level has been revealed in these layers and attributed to additional localized Mn states. In addition to a downward shift of the chemical potential with increasing Mn-doping, we find pronounced valence-band modifications, particularly in the case of the spin-split-off band, what disagrees with the pure impurity band model. The modulation photoreflectance spectroscopy results confirm the modifications of the valence band in the investigated layers.