Hole spin polarization in the exchange field of the dilute magnetic (Ga,Mn)As semiconductor studied by means of polarized hot-electron photoluminescence spectroscopy

We have studied the hole spin polarization in the exchange field of ferromagnetic (Ga, Mn) As by means of polarized hot-electron photoluminescence (HPL). We found that the holes contribute to the HPL spectrum in two very different states. Most of the holes are strongly localized on Mn acceptors whose spin polarization under circularly polarized excitation is not sensitive to the exchange field arising in the ferromagnetic state below the Curie point. In contrast, the spin polarization of weakly localized or delocalized holes strongly decreases below the Curie temperature. This effect is explained by the hole spin orientation in the exchange field. The spin splitting of the weakly localized or delocalized holes in the mean exchange field is estimated Delta similar or equal to 6 meV (equivalent to the built-in exchange field similar or equal to 90 T).