Band engineering of magnetic semiconductors by phosphorus doping

Impact of P and Mn incorporation into GaAs layers on their electronic- and band-structures as well as their magnetic and structural properties has been studied. A set of the homogenous (Ga,Mn)(P,As) layers with 8% of Mn and 0-32% of P contents 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 that a strongly dispersing band crosses the Fermi energy in the highly doped samples. This is a consequence of the high concentration of Mn-induced itinerant holes residing in the valence band of the III-V semiconductor host. We find an increased density of states near the Fermi level for higher doping levels, which one may attribute to additional localized Mn states. The spectroscopic ellipsometry (SE) results confirmed the modification of the valence band of the epitaxial layers.