Bulk electronic structure of the dilute magnetic semiconductor Ga1-xMnxAs through hard X-ray angle-resolved photoemission

A detailed understanding of the origin of the magnetism in dilute magnetic semiconductors is crucial to their development for applications. Using hard X-ray angle-resolved photoemission (HARPES) at 3.2 keV, we investigate the bulk electronic structure of the prototypical dilute magnetic semiconductor Ga0.97Mn0.03As, and the reference undoped GaAs. The data are compared to theory based on the coherent potential approximation and fully relativistic one-step-model photoemission calculations including matrix-element effects. Distinct differences are found between angle-resolved, as well as angle-integrated, valence spectra of Ga0.97Mn0.03As and GaAs, and these are in good agreement with theory. Direct observation of Mn-induced states between the GaAs valence-band maximum and the Fermi level, centred about 400meV below this level, as well as changes throughout the full valence-level energy range, indicates that ferromagnetism in Ga1-xMnxAs must be considered to arise from both p-d exchange and double exchange, thus providing a more unifying picture of this controversial material.